Comparative analysis of viscous characteristics of CPE–cellulose solutions in NMMO let us to conclusion, that the introduction of CPE into cellulose solutions does not change drastically profiles of flow curves or the concentration dependences of the viscosity inherent for binary solutions cellulose-NMMO. At low and intermediate shear rates, mixed solutions demonstrate Newtonian character of flow; at high shear rates, a marked viscosity anomaly is observed. The introduction of CPE into cellulose solutions increases their viscosity in whole range of shear rates. The concentration dependences of the viscosity of cellulose solutions show positive deviations from values corresponding to the logarithmic additivity rule. This indicates on strong intermolecular interactions between molecules of solvent and cellulose as well as between cellulose macromolecules themselves. The introduction of CPE macromolecules into the cellulose–NMMO system gives rise to even higher positive

Due to the specific structural features of cellulose and even despite its strong electron donor–acceptor interaction with NMMO, cellulose solutions in NMMO are known to be highly structured. Due to presence of CPE in NMMO, solvent quality decreases and interaction between cellulose macromolecules appears to be enhanced; as a result, the viscosity of the mixed solutions is increased. Therefore, the difference between binary and ternary solutions is concerned with the level of structural organization of cellulose

Hypothetically, the high level of structuring of the mixed solutions increases with increasing overall concentration of polymers and variation in the ratio between components. As a result, mixed solutions are metastable. This assumption was proven by rheological studies performed for mixed solutions cellulose and CPE in NMMO over a wide concentration

For example, at passing to 25% mixed solution concentration, which according to ternary phase diagram is located in vicinity of the binodal, the character of rheological behavior changes, especially in the regions of limiting concentrations (20% of cellulose/5% of PDTOB and 5% of cellulose/20% of PDTOB). For example, in the case of the 20/5 mixture viscosity anomaly at high shear stresses increases dramatically. Flow curves of the 5/20 mixture can change their position depending on prehistory of the sample and deformation conditions. Therefore, deformation of the solutions in their pre-transition region increases phase instability and can lead even to the phase separation. One can expect that for the mixed systems located directly on binodal, the effect of deformation will be the most pronounced. Figure 14 presents two flow curves for the cellulose-PDTOB (13/15) mixture. Curve 1 corresponds to short deformation times (strain is 10–100 rel. units), and in these conditions the system does not undergo phase separation. With increasing time of deformation action (strain is above 100 rel. units) the shear stress does not grow monotonically at each shear rate, but after reaching the definite strain decreases (stepwise curve). This kind of behavior

deviations of the concentration dependence of viscosity.

**Figure 14.** Flow curves of the mixed cellulose–PDTOB solutions in NMMO; overall concentration of polymers is 28%, and cellulose : PDTOB ratio = 13 : 15: (1) small strains, (2) high strains.

reflects transition through binodal induced by strain. By other words, after relaxation at stopping the previous shear rate, the system is homophase but deformation at flow acts as thermodynamic factor changing the bimodal location, and the system becomes heterophasic. Cessation of flow at each shear rate leads to stress relaxation and reverse transition into onephase region, but new loading causes the same transformation of the phase state. These results indicate on two circumstances: significant changes in the rheological behavior of mixed solutions on passing from the single-phase to the two-phase state, and influence of flow on location of the binodal curve.

Mixed cellulose–CPE solutions in NMMO with phase compositions corresponding to single phase region have been studied over a wide range of shear stresses with attempt to see morphological changes, they have not been revealed.

In contrast to the above systems, two-phase cellulose–PMPIA systems in NMMO are characterized by a well-pronounced heterogeneous morphology, which is controlled by the composition of the sample and deformation conditions. First, let us consider the specific features of the rheological behavior of mixed cellulose–PMPIA–NMMO systems under capillary flow. All solutions that contain 14, 18, and 20% of polymers show a non-Newtonian behavior or, in other words, their viscosity almost linearly decreases with increasing shear stress and follows the power-law flow regime.

The concentration dependences of the viscosity (log τ = 3.6 Pa) were constructed for equiconcentrated mixed solutions; the overall concentration of polymers in solutions was 14 or 18%. As follows from Fig.15, the viscosity of all the solutions lies below the line of logarithmic additivity.

**Figure 15.** Concentration dependences of viscosity of the mixed cellulose–PMPIA solutions in NMMO. The overall concentration of polymers is (1) 14 and (2) 18%.

Оn passing through the entrance zone, droplets of PMPIA solution (the dispersed phase) are elongated and transformed into long liquid threads oriented along the flow direction, forming a fibrillar system. As a result, inside the capillary a complex profile of linear velocities is realized (a multi-parabolic one). Due to the superposition of multiple profiles, the overall flow rate decreases.

In addition to capillary viscometry, the rheological behavior of the mixed cellulose–PMPIA solutions in NMMO was studied on a rotation rheometer with its cone–plate working unit. Measurements were performed under steady-state shear by measuring dependences of tangential (τ) and normal (N1) stresses on the shear rate and in the low-amplitude oscillatory deformation regime by measuring the frequency dependences of storage modulus G' and loss modulus G''. In the case of the first difference of normal stresses, their coefficient connecting N1 with shear rate was calculated: N1= ζ 2 .

Figure 16 presents the concentration dependences of the effective viscosity η and the coefficient of normal stresses. As follows from this figure, in contrast to the concentration dependences of viscosity constructed from data of capillary flow, the above mentioned dependences have S-shaped profiles with positive deviation at low concentrations and negative deviation at high concentrations. A slight positive deviation from additivity can be explained by different flow kinematics in rotation and capillary regimes leading to different orientation of the disperse phase droplets.

**Figure 15.** Concentration dependences of viscosity of the mixed cellulose–PMPIA solutions in NMMO.

Оn passing through the entrance zone, droplets of PMPIA solution (the dispersed phase) are elongated and transformed into long liquid threads oriented along the flow direction, forming a fibrillar system. As a result, inside the capillary a complex profile of linear velocities is realized (a multi-parabolic one). Due to the superposition of multiple profiles,

In addition to capillary viscometry, the rheological behavior of the mixed cellulose–PMPIA solutions in NMMO was studied on a rotation rheometer with its cone–plate working unit. Measurements were performed under steady-state shear by measuring dependences of tangential (τ) and normal (N1) stresses on the shear rate and in the low-amplitude oscillatory deformation regime by measuring the frequency dependences of storage modulus G' and loss modulus G''. In the case of the first difference of normal stresses, their coefficient

Figure 16 presents the concentration dependences of the effective viscosity η and the coefficient of normal stresses. As follows from this figure, in contrast to the concentration dependences of viscosity constructed from data of capillary flow, the above mentioned dependences have S-shaped profiles with positive deviation at low concentrations and negative deviation at high concentrations. A slight positive deviation from additivity can be explained by different flow kinematics in rotation and capillary regimes leading to different

.

The overall concentration of polymers is (1) 14 and (2) 18%.

connecting N1 with shear rate was calculated: N1= ζ 2

orientation of the disperse phase droplets.

the overall flow rate decreases.

**Figure 16.** (a) Viscosity η and (b) coefficient of normal stresses ζ vs. composition for the mixed cellulose–PMPIA solutions in NMMO at log τ = (1) 3 and (2) 4 Pa. The overall concentration of polymers is 18%.

The use of the transparent cell as the working unit in the rotation rheometer allowed us to perform the direct visual observation of the behavior of mixed systems under flow. Upon deformation in an uniform shear field, mixed solutions containing from 5 to 40% of PMPIA are transformed into a microheterogeneous system with a highly developed interfacial surface. In the case of 5% content of PMPIA solution, the shear deformation is insufficient to provide any deformation of droplets and they play a role of filler. When the content of the PMPIA phase is increased, the dimensions of droplets increase and the deformation induce the transformation of the droplet-matrix morphology into the fibrillar one. The formation of liquid continuous threads of the dispersed low-viscous phase is accompanied by negative deviations of the concentration dependences of the viscosity from the additive straight line, similar to the case of the capillary flow.

The concentration dependences of *G*' and *G*'' as well as steady-state viscosity are S-shaped. According to the traditional concept on the character of flow of incompatible polymer systems, the transition the positive to the negative deviations of viscosity from the additivity line is treated as phase inversion. In our case, the revealed dependences are controlled by changes in the morphology of the flowing mixed system and by its ability for orientation at different by intensity deformation actions.

**Figure 17.** (1) Storage G' and (2) loss moduli G'' vs. composition at ω = 1 s–1 for the mixed cellulose– PMPIA solutions in NMMO. The overall concentration of polymers is 18%.

Scales of positive and negative deviations can be selected as criteria of the deformability of PMPIA droplets. Depending on droplets deformability at different flow regimes, the interval of inflection shifts along the concentration axis. Maximum positive deviation is for the oscillatory regime. In this case, the point corresponding to the transition to negative deviations is observed at 50–60% PMPIA content. In a homogeneous shear field (under steady-state flow), positive deviations of viscosity are much lower and take place in the concentration interval below 30–40%. Finally, under capillary flow, no positive deviations are observed and maximal viscosity is achieved at ~65% of PMPIA.

Hence, solutions of cellulose and LC copolyesters in NMMO far from binodal change their rheological characteristics according to the traditional mechanism of flow of mixed systems with high specific interaction between components. However, in vicinity of bimodal deformation induces phase transition from the homogeneous to the heterogeneous system leading to unstable flow with oscillation of shear stress. In the case of the mixed cellulose– PMPIA–NMMO systems, the rheological behavior is controlled by transformations of morphology dependent on solution composition and flow regime.

### *4.2.4. Rheological Characteristics of Mixed Solutions of Cellulose with Natural and Modified Clays*

324 Cellulose – Fundamental Aspects

**Figure 17.** (1) Storage G' and (2) loss moduli G'' vs. composition at ω = 1 s–1 for the mixed cellulose–

Scales of positive and negative deviations can be selected as criteria of the deformability of PMPIA droplets. Depending on droplets deformability at different flow regimes, the interval of inflection shifts along the concentration axis. Maximum positive deviation is for the oscillatory regime. In this case, the point corresponding to the transition to negative deviations is observed at 50–60% PMPIA content. In a homogeneous shear field (under steady-state flow), positive deviations of viscosity are much lower and take place in the concentration interval below 30–40%. Finally, under capillary flow, no positive deviations

Hence, solutions of cellulose and LC copolyesters in NMMO far from binodal change their rheological characteristics according to the traditional mechanism of flow of mixed systems with high specific interaction between components. However, in vicinity of bimodal deformation induces phase transition from the homogeneous to the heterogeneous system leading to unstable flow with oscillation of shear stress. In the case of the mixed cellulose– PMPIA–NMMO systems, the rheological behavior is controlled by transformations of

PMPIA solutions in NMMO. The overall concentration of polymers is 18%.

are observed and maximal viscosity is achieved at ~65% of PMPIA.

morphology dependent on solution composition and flow regime.

In order to estimate the effect of aluminosilicate additives on the rheological behavior of cellulose solutions in NMMO, rheological properties of filled solutions containing 18 and 10% cellulose were chosen as matrices [14-15]. It was shown that flow of sufficiently viscous 18% cellulose solutions filled up to 9% with different clays is determined mainly by rheological behavior of the polymer matrix. Using less concentrated 10% cellulose solutions allowed to increase the clay content in the solutions up to 20%. The flow curves for 10% cellulose solutions filled to various degree with particles of Cloisite Na+ are presented in Fig. 18. As is seen from the figure, already at a low content of solid phase the flow of the filled composition becomes a non-Newtonian.

With increasing clay concentration the degree of the viscosity anomaly increases, and at 20% content of clay in the system the shape of flow curve indicates on existence of the yield stress (viscoplastic behavior) due to the formation by filler particles the percolation network. At high shear rates the structure of clay is destroyed, and as a result the rheological behavior becomes similar (pseudoplastic behavior) to cellulose solution in NMMO.

Introducing to the 10% cellulose solution hydrophobic clay - Cloisite 20A is caused some intrinsic features of rheological behavior. The identified features of the rheological behavior of these compositions are presented in Fig. 19 as the generalized concentration dependence of the relative viscosity for both 18% and 10% of matrices containing hydrophilic Cloisite Na+ and organoclay Cloisite 20A.

For easier comparison, the function is the relative viscosity (ηr=η/ηcel) , and the argument is a fraction of clay in composition. At the solid content up to 9%, changes of relative viscosity with concentration for all compositions can be described by a single curve, irrespectively of the clay nature and the matrix viscosity. With further increasing of the solid phase concentration the dependence becomes more complex. The single the viscositycomposition curve for solutions filled with Cloisite Na+ particles does not change, but introduction to solution particles of Cloisite 20A clay leads to a splitting of the curve into two branches. A high viscous branch (curve 1) practically coincident with the concentration curve of systems with natural clay, a low viscous branch lies much lower (curve 2), that is why the generalized dependence for these compositions has a minimum localized at 10% of clay in solution. Starting with concentration corresponding to the splitting, the flow curves of filled solutions containing 15% - 20% of Cloisite 20A demonstrate the presence of the yield stress.

Unexpected at first sight the experimental fact of reduction of the viscosity of filled solutions with Cloisite 20A (curve 2) seems to be explained by different prehistory of their preparation. Within variety of many factors that determine the specific features of systems under investigation, as the main parameter the moisture content in "initially hydrophobic" clay was chosen, since all other components are hydrophilic containing almost equilibrium moisture, meanwhile the sorption of water by hydrophobic clay was unknown.

**Figure 18.** Flow curves for 10% solutions of cellulose in NMMO with Cloisite Na+. Content of clay: 0 (1), 5 (2), 10 (3), 15 (4), 20 wt.% (5). Filled points - rotational viscometry data, open points - data of capillary viscometry.

**Figure 19.** Concentration dependence of the relative viscosity filled solutions of cellulose in NMMO with Cloisite Na+ and Cloisite 20A at log τ = 3.0 [Pa]. 1-18% solution of cellulose + Cloisite Na+; 2 - 18% solution of cellulose + Cloisite 20A, 3 - 10% solution of cellulose + Cloisite Na+; 4 -10% solution of cellulose + Cloisite 20A. Figures 5, 6 and 7 correspond to 6, 13 and 16% of moisture content in Cloisite 20A.

Model experiments on influence of moisture content in Cloisite 20A on the viscosity values using pre-moistened clay with a fixed water content were carried out. Obtained results have confirmed the assumption that a decrease in the viscosity of filled solution is caused by increase of water content in the clay. By means of X-ray diffraction method, a comparative structure analysis of the neat clay (~ 2% of water) and extremely Cloisite 20A moistened after prolonged sorption up to 16% of water it was shown that the basal reflection of neat clay at 2, equal to 3,2 transforms to diffuse asymmetric reflection with maxima at 2 2,6 and 3.9 for moistened clay (Fig. 20). Such change of the diffraction pattern indicates on specific ability of clay hydrophobized with quarterly ammonium bases to absorb water. We can expect that water molecules should come to the polar Na+ center of ionic surfactant localized on negative clay platelets. On the one side, this can lead to increase of the interplanar spaces, i.e., to decrease of the intrinsic scattering angle, but on the other side, presence of polar water molecules in vicinity of hydrophilic clay elementary platelets could cause hydrophobic interaction (repulsion) that change conformations of hydrophobic tails of modifier leading to their shrinking. As a result of dual action of water molecules, the interspace width change in non-homogeneous manner (extension-shrinkage).

326 Cellulose – Fundamental Aspects

1

viscometry.

20A.

2

3

4

lg [Па]

**Figure 18.** Flow curves for 10% solutions of cellulose in NMMO with Cloisite Na+. Content of clay: 0 (1), 5 (2), 10 (3), 15 (4), 20 wt.% (5). Filled points - rotational viscometry data, open points - data of capillary

**Figure 19.** Concentration dependence of the relative viscosity filled solutions of cellulose in NMMO with Cloisite Na+ and Cloisite 20A at log τ = 3.0 [Pa]. 1-18% solution of cellulose + Cloisite Na+; 2 - 18% solution of cellulose + Cloisite 20A, 3 - 10% solution of cellulose + Cloisite Na+; 4 -10% solution of cellulose + Cloisite 20A. Figures 5, 6 and 7 correspond to 6, 13 and 16% of moisture content in Cloisite

lg [c -1 ]

> Rheological data show that 10% content of clay in the system is critical, at which heterophase structure of the interplanar spaces forms and can initiate distortion of clay crystalline structure with formation of irregular layers. Shear action can cause fragmentation of clay platelets ensembles accompanied by a drop in the viscosity of the system as whole.

> Introduction to the cellulose solutions of nanoparticles of M2Cloisite Na+ in amount not exceeding 0.1% leads to decrease of the solutions viscosity more than in two times (Fig. 21).

> Filled solutions of cellulose in NMMO with addition of nanoparticles of M2Cloisite Na+ are characterized by a pronounced fibrillation. Apparently, the reason of reducing the viscosity is directly related to the fibrillar structure of cellulose solutions in presence of clay nanoparticles and extremely high surface energy of highly developed interfaces.

**Figure 20.** Diffraction patterns of the neat Cloisite 20A (1) and moistened Cloisite 20A (2).

**Figure 21.** Dependence of the viscosity on concentration of M2Cloisite Na+; a) Microphotography of 18% cellulose solution with 0,03% M2Cloisite Na+.

The rheological behavior of filled solutions of cellulose with microparticles of Cloisite Na+ and Cloisite 20A is similar to the behavior of traditional polymer filled systems, while in presence of nanoparticles the flow mechanism changes from traditional segmental to stratified one, i.e., stream morphology becomes regular.

## **5. Evolution of cellulose structure at transition from dopes to cellulose and blend oriented fibers**

#### **5.1. Structure of cellulose and its blends with synthetic polymers**

X-ray data demonstrate that solutions containing 18% cellulose in NMMO are amorphous and isotropic, as evidenced by the short-range order in the arrangement of macromolecules. The bulk extrudate obtained without drawing after full removal of the solvent is likewise isotropic, as is seen from X-ray patterns shown in Fig. 22a.

Spinning of fibers from 18% cellulose solution leads to substantial changes in the cellulose structure. The as-spun fiber containing the residual solvent is characterized by nonequilibrium metastable modification of cellulose. The X-ray pattern of this sample (Fig.21b) exhibits well-defined equatorial reflections. Presence of only one intense reflection on the equator of the diffractogram implies that the intensity abruptly declines with the diffraction angle 2θ. This effect is usually attributed to an increase in the disorder owing to the formation of disruptions along chains. A similar character of diffractograms, as a rule, is typical for 2*D* columnar mesophases. During complete phase separation, a crystalline phase of the cellulose is formed (Fig. 22c).

**Figure 21.** Dependence of the viscosity on concentration of M2Cloisite Na+; a) Microphotography of

**5. Evolution of cellulose structure at transition from dopes to cellulose**

X-ray data demonstrate that solutions containing 18% cellulose in NMMO are amorphous and isotropic, as evidenced by the short-range order in the arrangement of macromolecules. The bulk extrudate obtained without drawing after full removal of the solvent is likewise

Spinning of fibers from 18% cellulose solution leads to substantial changes in the cellulose structure. The as-spun fiber containing the residual solvent is characterized by nonequilibrium metastable modification of cellulose. The X-ray pattern of this sample (Fig.21b) exhibits well-defined equatorial reflections. Presence of only one intense reflection on the equator of the diffractogram implies that the intensity abruptly declines with the diffraction angle 2θ. This effect is usually attributed to an increase in the disorder owing to the formation of disruptions along chains. A similar character of diffractograms, as a rule, is typical for 2*D* columnar mesophases. During complete phase separation, a crystalline phase

**5.1. Structure of cellulose and its blends with synthetic polymers**

The rheological behavior of filled solutions of cellulose with microparticles of Cloisite Na+ and Cloisite 20A is similar to the behavior of traditional polymer filled systems, while in presence of nanoparticles the flow mechanism changes from traditional segmental to

а)

18% cellulose solution with 0,03% M2Cloisite Na+.

**and blend oriented fibers**

of the cellulose is formed (Fig. 22c).

stratified one, i.e., stream morphology becomes regular.

isotropic, as is seen from X-ray patterns shown in Fig. 22a.

**Figure 22.** Flat camera X-ray patterns of 18% solution of cellulose in NMMO (а), cellulose partially washed-out from NMMO (b) and completely coagulated oriented cellulose fibers (c).

During spinning of the cellulose fiber from NMMO solutions, there appears a crystalline phase in which long crystallites are extended in the longitudinal direction [16-18]. On the one hand, this situation indicates on high order and increased density of the structure being formed. On the other hand, this leads to decrease of the probability of transverse hydrogen bonds with neighboring crystalline clusters formation enhancing the tendency of the system toward fibrillation. The transformation of structure in the cellulose–NMMO system during the spinning of model fibers is schematically shown in Fig. 23.

A comparison of X-ray pattern taken for the crystalline fiber (Fig. 22c) and the gel fiber (Fig.22b) of cellulose leads us to suggestion that the package of macromolecules in the plane of the 2D mesophase and the ac plane of the crystal are similar. This conclusion is supported by the fact that the angular positions of the equatorial reflections of the crystal and the mesophase are similar. The transition of the cellulose–NMMO system to the mesophase is probably related to the structural features of cellulose as a high-regular polymer with a developed system of H-bonds.

**Figure 23.** Schematic representation of the evolution in the cellulose structure during spinning of fiber samples from cellulose solutions in NMMO

Let us consider the evolution of the cellulose structure in blends. According to the X-ray data, all NMMO solutions of cellulose blended with copolyesters, PMPIA or clays, are amorphous; however, the character of structural transformations in them during isolation of the polymer phase is appreciably different from that in cellulose solutions [19]. Our experiments showed that although the chemical nature of the polymer introduced in cellulose solutions and the phase states and morphologies of blend solutions are different, the resultant structure of the formed blend polymer phase is of the same type. Since the evolution of the structure is the most pronounced for the cellulose–PMPIA system, let us examine step-by-step formation of the structure of cellulose composites.

After removal of the solvent, cellulose composites containing 5% PMPIA, as is seen from the diffractograms shown in Fig. 24, are not amorphous even in the absence of drawing, and demonstrate a marked increase in the intensity of scattering in the range of angles 2θ = 12° in the equatorial direction and the absence of redistribution between equatorial and meridional scatterings at 2θ > 15° (Figs. 24, 25a).

Presence of two peaks on the diffractogram indicates that the packing with two mean intermolecular spacings occurs. These spacings are appreciably different. It is quite probable that the molecules located in the closest proximity more easily form the system of inter- and intramolecular hydrogen bonds that is necessary for formation of ordered domains capable to be oriented. Therefore, the layered 1D packaging is formed at a small draw ratio (λ = 6) (Fig. 25a).

**Figure 24.** Equatorial (1) and meridional (2) diffractograms of blend extrudates composed of 95% cellulose and 5% PMPIA

(Fig. 25a).

cellulose and 5% PMPIA

Let us consider the evolution of the cellulose structure in blends. According to the X-ray data, all NMMO solutions of cellulose blended with copolyesters, PMPIA or clays, are amorphous; however, the character of structural transformations in them during isolation of the polymer phase is appreciably different from that in cellulose solutions [19]. Our experiments showed that although the chemical nature of the polymer introduced in cellulose solutions and the phase states and morphologies of blend solutions are different, the resultant structure of the formed blend polymer phase is of the same type. Since the evolution of the structure is the most pronounced for the cellulose–PMPIA system, let us

After removal of the solvent, cellulose composites containing 5% PMPIA, as is seen from the diffractograms shown in Fig. 24, are not amorphous even in the absence of drawing, and demonstrate a marked increase in the intensity of scattering in the range of angles 2θ = 12° in the equatorial direction and the absence of redistribution between equatorial and

Presence of two peaks on the diffractogram indicates that the packing with two mean intermolecular spacings occurs. These spacings are appreciably different. It is quite probable that the molecules located in the closest proximity more easily form the system of inter- and intramolecular hydrogen bonds that is necessary for formation of ordered domains capable to be oriented. Therefore, the layered 1D packaging is formed at a small draw ratio (λ = 6)

**Figure 24.** Equatorial (1) and meridional (2) diffractograms of blend extrudates composed of 95%

examine step-by-step formation of the structure of cellulose composites.

meridional scatterings at 2θ > 15° (Figs. 24, 25a).

**Figure 25.** X-ray patterns of blend fiber samples composed of 95% cellulose and 5% PMPIA at various draw ratios: λ = (a) 6, (b) 13, and (c) 17.

Formation of composite fibers under conditions of orientation drawing accompanies by further evolution in the scattering pattern. As is seen from Fig. 25b, the redistribution of intensity covers now the entire region of scattering. As in the case of the purely cellulose mesomophic gel fiber, two reflections are observed on the equator (22 b). As the order of packing of cellulose macromolecules in the basal plane (at the intermolecular level) is improved, the transition of the layered 1D packing to the 2D columnar mesophase occurs. In this case, the position of equatorial reflections on the X-ray patterns of the oriented blend sample coincides with the position of equatorial reflections of the mesophase cellulose gel fiber and with the position of main basal reflection 101 of the cellulose crystal.

An increase in the draw ratio of the composite sample to λ = 17 facilitates further perfection of its structure. On the X-ray pattern of the fiber (Fig. 25c), the meridional reflection appears at 2θ =35°C. The features of scattering in the vicinity of the equator, which have been previous assigned to ordering in the basal plane, are preserved. At the same time, there are no reflections in the quadrants of the X-ray pattern.

A comparison of the oriented fibers of cellulose and the composite having the same draw ratios convincingly proves this finding. In fact, scanning of the composite fiber samples reveals no near-meridional reflections or other quadrant reflections (Fig. 26). The absence of quadrant reflections is the distinguishing feature of the composite fiber. At the same time, the angular positions and the half-widths of equatorial and meridional reflections for the cellulose and composite fibers are almost the same at a small content of the polymer additive (4%).

The above described picture of scattering obtained for the composite fiber with λ = 17 shows that the system contains two independent levels of order: 2D order in the basal plane (the intermolecular level) and 1D order along the fiber axis (the intramolecular level), that is, on the whole, non-crystalline 3D order. Fig. 27 schematically represents the most pronounced structural transformations occurring during isolation of the polymer phase from blend solutions in NMMO.

**Figure 26.** Diffractograms of the composite cellulose fiber containing 4% PMPIA during scanning (1) along the meridian and at angles to the meridian of (2) 10° and (3) 20°.

Thus, it has been shown for the first time that the introduction of copolyester and PMPIA into cellulose solutions in NMMO makes it possible to govern the processes of cellulose structuring and to stop them at the stage of formation of the 2D mesophase and, thus, to avoid further perfection of the structure and formation of the crystalline phase of cellulose.

On the basis of the above evidence, evolution in the structure of cellulose during isolation of the polymer phase from its own solutions and solutions of cellulose blends in NMMO may be depicted as follows. If the cellulose fiber is spun from NMMO solutions under the conditions of uniaxial drawing, the structure of cellulose forms in two stages. At the first stage, when the solvent is incompletely removed from solution (~95%) and, accordingly, the phase separation is incomplete, regular interchain periodicity develops in the main bulk of the cellulose phase. NMMO molecules remaining in the polymer phase are linked via strong electron donor–acceptor bonds with protons of hydroxyl groups of cellulose and, thus, favor restoration of intrachain hydrogen bonds that are necessary for the formation of classical three-dimensional ordering. As a consequence, conformational distortions appear in chains and only the two-dimensional ordering of the 2D mesophase type is implemented in the system. At the second stage, when the solvent is fully removed and, accordingly, when the phase decomposition in the cellulose phase is completed, the traditional ensemble of inter and intramolecular hydrogen bonds forms and cellulose passes to the crystalline phase.

Copolyester and PMPIA are thermodynamically incompatible with cellulose but possess high affinity for NMMO. These polymers dissolve in NMMO to form solutions that in the case of copolyester are compatible with the solution of cellulose. However, in the case of PMPIA, the inverse situation is observed: solutions of cellulose and PMPIA in the same solvent are incompatible. During isolation of the polymer phase from blend solutions, the redistribution of specific interactions and hydrogen bonds, but conformational transformations of cellulose macromolecules associated with incompatibility of polymers most probably create steric hindrances to the development of intermolecular ordering that is traditional for cellulose.

332 Cellulose – Fundamental Aspects

**Figure 26.** Diffractograms of the composite cellulose fiber containing 4% PMPIA during scanning (1)

Thus, it has been shown for the first time that the introduction of copolyester and PMPIA into cellulose solutions in NMMO makes it possible to govern the processes of cellulose structuring and to stop them at the stage of formation of the 2D mesophase and, thus, to avoid further perfection of the structure and formation of the crystalline phase of cellulose.

On the basis of the above evidence, evolution in the structure of cellulose during isolation of the polymer phase from its own solutions and solutions of cellulose blends in NMMO may be depicted as follows. If the cellulose fiber is spun from NMMO solutions under the conditions of uniaxial drawing, the structure of cellulose forms in two stages. At the first stage, when the solvent is incompletely removed from solution (~95%) and, accordingly, the phase separation is incomplete, regular interchain periodicity develops in the main bulk of the cellulose phase. NMMO molecules remaining in the polymer phase are linked via strong electron donor–acceptor bonds with protons of hydroxyl groups of cellulose and, thus, favor restoration of intrachain hydrogen bonds that are necessary for the formation of classical three-dimensional ordering. As a consequence, conformational distortions appear in chains and only the two-dimensional ordering of the 2D mesophase type is implemented in the system. At the second stage, when the solvent is fully removed and, accordingly, when the phase decomposition in the cellulose phase is completed, the traditional ensemble of inter and intramolecular hydrogen bonds forms and cellulose passes to the crystalline phase.

Copolyester and PMPIA are thermodynamically incompatible with cellulose but possess high affinity for NMMO. These polymers dissolve in NMMO to form solutions that in the case of copolyester are compatible with the solution of cellulose. However, in the case of PMPIA, the inverse situation is observed: solutions of cellulose and PMPIA in the same

along the meridian and at angles to the meridian of (2) 10° and (3) 20°.

**Figure 27.** Schematic representation of the structure evolution during spinning of composite fibers from the cellulose–NMMO–

PMPIA blend system: (a) 1D order in the basal plane (layered, intermolecular); (b) 2D order in the basal plane (intermolecular); and (c) 2D order in the basal plane (intermolecular) + 1D order along the fiber axis (intramolecular), that is, →3D noncrystalline order.

#### **5.2. Structure of cellulose and its blends with aluminosilicates**

The evolution of structure transformations in composite systems based on cellulose and layered aluminosilicates Cloisite Na+ and Cloisite 20Å, obtained through a stage of solidphase dissolution of cellulose in NMMO, has been investigated by X-ray diffraction (XRD) technique [20-22]. A solid-phase process provides high dispersion and uniform distribution of particles of clay in a matrix cellulose phase.

Diffractograms in Fig.28 reflect interaction between components of the system "cellulose-Cloisite Na+-NMMO" realized on the first stage of the process—the solidstate activation.

**Figure 28.** Diffractograms of Cloisite Na+ (1), solid-activated mix system: 16,2% cellulose - 1,8% Cloisite Na+ - 82% ММО at 20 (2), 120 (3) and 20oC after cooling from 1200С (4)

Comparison of the X-ray characteristics indicates that after introducing the clay into the composition no changes in the angular position of the basic layer peak of the clay at 2θL take place. However, an additional peak appears shifted a little to a small-angle side in comparison with the reflection at 2θL. The shift of the additional new peak corresponds to the increase of interlayer spacing for 3 Å. This additional peak becomes the basic one on heating up to 120°С (curve 3) and subsequent cooling (curve 4). It seems that the weak changes in clay interlayer spacing are caused by water migration from the system to the clay due to their high affinity to each other. So, the XRD pattern of the solid-phase treated by composition corresponds to the superposition of the two patterns: Cloisite Na+ and the solid pre-solution of cellulose in NMMO.

The scanning at a low speed with high acquisition reveals no reflexes in the angular region of 2θ <3°, that did not enables us treat this system as an intercalated one.

Nanosize particles (M2Cloisite Na+), received as a result of activating dispersion of Cloisite Na+, are discrete tacktoids with the same interlayer distance as in the initial clay. Possibly, such type of a clay structure is caused by steric restriction for the penetration of bulk Hcomplexes into interlayer regions of the polar montmorillonite Cloisite Na+.

Essentially different structure of activated solid-phase mixed system is realized in Cloisite 20 A. As seen at the equatorial XRD pattern of the composition (Fig. 29), the basic layer peak of Cloisite 20A shifts to the small-angle region from the initial angular position 2L=3.3º to 2L=1.76°, (curve 1).

334 Cellulose – Fundamental Aspects

**I, ar.un.**

0

pre-solution of cellulose in NMMO.

500

1000

10 20 30 40

**Figure 28.** Diffractograms of Cloisite Na+ (1), solid-activated mix system: 16,2% cellulose - 1,8% Cloisite

Comparison of the X-ray characteristics indicates that after introducing the clay into the composition no changes in the angular position of the basic layer peak of the clay at 2θL take place. However, an additional peak appears shifted a little to a small-angle side in comparison with the reflection at 2θL. The shift of the additional new peak corresponds to the increase of interlayer spacing for 3 Å. This additional peak becomes the basic one on heating up to 120°С (curve 3) and subsequent cooling (curve 4). It seems that the weak changes in clay interlayer spacing are caused by water migration from the system to the clay due to their high affinity to each other. So, the XRD pattern of the solid-phase treated by composition corresponds to the superposition of the two patterns: Cloisite Na+ and the solid

The scanning at a low speed with high acquisition reveals no reflexes in the angular region

Nanosize particles (M2Cloisite Na+), received as a result of activating dispersion of Cloisite Na+, are discrete tacktoids with the same interlayer distance as in the initial clay. Possibly, such type of a clay structure is caused by steric restriction for the penetration of bulk H-

Essentially different structure of activated solid-phase mixed system is realized in Cloisite 20 A. As seen at the equatorial XRD pattern of the composition (Fig. 29), the basic layer peak

of 2θ <3°, that did not enables us treat this system as an intercalated one.

complexes into interlayer regions of the polar montmorillonite Cloisite Na+.

Na+ - 82% ММО at 20 (2), 120 (3) and 20oC after cooling from 1200С (4)

4

3

2

1

**2, degrees**

**Figure 29.** Diffractograms of the solid-phase activated system 16,2% cellulose-1,8% Cloisite 20A - 82% ММО at 20 (1), 120 (2), 20С after cooling from 120С (3) and Cloisite 20A (4).

That is caused by the influence of shear stress. Molecules of cellulose and NMMO penetrate into interlayer regions of the clay crystal lattice causing to the shift one-dimensional expansion by more than 20Å. It happens in spite of the hydrophobic nature of Cloisite 20A conditioned due to the presence of non-polar side modifying substituents. A heating and, accordingly, melting of mixed "solid" pre-solutions, they transfer into a viscous state that leads to the changes in the XRD pattern (curve 2): the intensity of the basic layer peak of the modified clay sharply increases and the angular position of this peak slightly shifts towards wide- angle side up to 2L=2.04º. The similar changes in the character of the XRD pattern occur also on heating the individual Cloisite 20A. This is apparently connected with conformational changes of its side chains. Conformational reorganization happened on heating promotes the formation of more perfect and homogeneous structure also after cooling the sample. This manifests itself by the intensive growth of the peak at 2L (curve 3).

The above cited set of experimental data allows us to come to the following conclusions. Under the solid-phase activation of a cellulose-NMMO-Cloisite Na+ system the solid-phase complex formation between molecules of cellulose and NMMO occurs only. As for the system cellulose-NMMO- Cloisite 20А, herein a reaction of solid-phase intercalation of molecules of cellulose and NMMO into the interlayer regions of the modified clay happens alongside with processes of H-complex formation between cellulose and NMMO.

Under simultaneous influence of temperature and velocity gradient solid-phase presolutions melt and passes into a viscous state. As seen in Fig. 30, the XRD patterns of mixed solutions of cellulose in NMMO, containing Cloisite Na+, are characterized by the slight shift of the basic layer peak of the clay towards the small-angle side, i.e. identically to what happens in solid-phase state.

Moreover, the basic layer peak of the clay at 2θL is characterized by higher intensity on the equator in comparison with the meridian (Fig. 30). Such character of azimuthal redistribution of peak intensity is obliged to high-degree orientation of discrete clay particles along the flow axis direction. It is achieved under the influence of longitudinal and shear stresses arising in the pre-entered zone of a capillary. Schematic representation of the realized structure is presented in Fig. 30a.

The structures of the mixed solutions of cellulose in NMMO, containing Cloisite 20А, and the activated solid-phase compositions are completely identical and are characterized by pronounced intercalation of the cellulose macromolecules solvated by NMMO into interlayer regions of the clay.

The revealed structural peculiarities of the mixed systems under study demonstrate themselves the most essentially at the last stage of the process – allocation of a cellulosesilicate phase from NMMO solutions.

**Figure 30.** Diffractograms of Cloisite Na+ (1), 18% cellulose solution in NMMO, containing 10% Cloisite Na+, in film form (2), in extrudate form (3 – meridional, 4 – equatorial) and schematic representation of the solution extrudate structure (a).

The XRD patterns of oriented samples of the cellulose-Cloisite Na+ compositions (Fig. 31) are characterized by the practically similar slight increase of the clay interlayer spacing dL up to 15.0Å, like in the case of the activated solid-phase mixtures and solutions described ealier. Such a character of the XRD patterns is indicative of complete absence of intercalation.

336 Cellulose – Fundamental Aspects

happens in solid-phase state.

interlayer regions of the clay.

silicate phase from NMMO solutions.

the solution extrudate structure (a).

realized structure is presented in Fig. 30a.

molecules of cellulose and NMMO into the interlayer regions of the modified clay happens

Under simultaneous influence of temperature and velocity gradient solid-phase presolutions melt and passes into a viscous state. As seen in Fig. 30, the XRD patterns of mixed solutions of cellulose in NMMO, containing Cloisite Na+, are characterized by the slight shift of the basic layer peak of the clay towards the small-angle side, i.e. identically to what

Moreover, the basic layer peak of the clay at 2θL is characterized by higher intensity on the equator in comparison with the meridian (Fig. 30). Such character of azimuthal redistribution of peak intensity is obliged to high-degree orientation of discrete clay particles along the flow axis direction. It is achieved under the influence of longitudinal and shear stresses arising in the pre-entered zone of a capillary. Schematic representation of the

The structures of the mixed solutions of cellulose in NMMO, containing Cloisite 20А, and the activated solid-phase compositions are completely identical and are characterized by pronounced intercalation of the cellulose macromolecules solvated by NMMO into

The revealed structural peculiarities of the mixed systems under study demonstrate themselves the most essentially at the last stage of the process – allocation of a cellulose-

**Figure 30.** Diffractograms of Cloisite Na+ (1), 18% cellulose solution in NMMO, containing 10% Cloisite Na+, in film form (2), in extrudate form (3 – meridional, 4 – equatorial) and schematic representation of

alongside with processes of H-complex formation between cellulose and NMMO.

**Figure 31.** Equatorial (1) and meridional (2) diffractograms and X-ray pattents (3) of composite sample of 90% cellulose + 10% Cloisite Na+; meridional diffractogram of cellulose fibers (4) powder diffractogram of Cloisite Na+ (5).

Analysis of the X-ray patterns of oriented samples allows us to obtain more exact information about realized structure. So, two equatorial peaks rather legibly manifest themselves on the equator of pattern of a mixed sample (Fig. 31a). One of the peaks located in at wide angles corresponds to the oriented cellulose. The angular positions of the equatorial peaks of cellulose on the patterns for mixed system (Fig. 31a) and oriented cellulose partially washed-out from NMMO (22b) coincide. As has been mentioned above, the presence of only these equatorial peaks indicates that cellulose macromolecules form the columnar type 2D-mesophase. The peak of oriented clay is also present on the equator of the mixture pattern. Is has been also established that the degree of orientation for both components depends on a content of nanocomposites. The increase of content and, accordingly, the degree of structuredness of cellulose phase in solution promotes the rise of an orientation order for both, cellulose itself and clay. The X-ray patterns of composite with Cloisite 20A and composite of cellulose with Cloisite Na+ as additive are practically identical.

Thus, a cellulose phase under the influence of shear stress is oriented and this initiates the implementation of certain orientational order of anizodiametric clay particles. The oriented clay particles give an additional impact on orienting the cellulose phase. In other words, in mixed solutions and respectively in the composites develop a unique synergy of orientation of the matrix phase and the filler. At the same time, particles of the clay immobilized in the matrix phase retain their size and do not aggregated.

Apparently, under the influence of shear of mixed systems at capillary flow anisodiametric solid particles of the filler embedding in a less structured region of the matrix phase, orient in the direction of extrusion. This leads to a perturbation of the stress and velocity fields of a viscoelastic matrix phase of cellulose and, consequently, to its local deformation. The stressed state of the matrix at the micro level does not allow the cellulose macromolecules rearrange with the formation a three-dimensional crystal structure. As a result, twodimensional but not three-dimensional structure is formed, and it is characterized by a regular packing of conformationally disordered macromolecules of cellulose in the basal plane. Schematic representation of the evolution in the cellulose structure during spinning of fiber samples from mixed solutions of cellulose in NMMO with the addition of nanoparticles of clay is presented in Fig. 32.

**Figure 32.** Schematic representation of the structure evolution during spinning of composite fibers from the cellulose–clay–NMMO blend system.

So, it has been shown that the introduction of copolyester, PMPIA and clays into cellulose solutions in NMMO makes it possible to govern the processes of the cellulose structuring and to finish them on the stage of the 2*D* mesophase formation and, thus, to avoid further perfection of the structure and the formation of the crystalline phase of cellulose. In other words, the structural situation is the same as in the case of the as-spun cellulose fibers. The only difference is that, in purely cellulose fibers, the resulting mesophase is not at equilibrium, while in blend systems, the 2*D* mesophase forms after the complete phase decomposition of the system and, correspondingly, is at equilibrium.

## **6. Fibrillization and mechanical properties of cellulose and synthetic polymers and layered aluminosilicates micro- and nanocomposite fibers**

The following structure peculiarity of the process under discussion was found. This is the formation of mesamorphic matrix cellulose phase due to introducing synthetic polymers or micro- and nanoadditives of layers alumonosilicates into cellulose solutions. This effect allows us to solve two important concerns of the processing of cellulose from solution in NMMO: it prevents fibers fibrillation and provides high mechanical properties of novel composite materials. Photomicrographs of cellulose and mixed fibers obtained before and after vibrating mill treatment are shown in Fig. 33.

338 Cellulose – Fundamental Aspects

nanoparticles of clay is presented in Fig. 32.

from the cellulose–clay–NMMO blend system.

Apparently, under the influence of shear of mixed systems at capillary flow anisodiametric solid particles of the filler embedding in a less structured region of the matrix phase, orient in the direction of extrusion. This leads to a perturbation of the stress and velocity fields of a viscoelastic matrix phase of cellulose and, consequently, to its local deformation. The stressed state of the matrix at the micro level does not allow the cellulose macromolecules rearrange with the formation a three-dimensional crystal structure. As a result, twodimensional but not three-dimensional structure is formed, and it is characterized by a regular packing of conformationally disordered macromolecules of cellulose in the basal plane. Schematic representation of the evolution in the cellulose structure during spinning of fiber samples from mixed solutions of cellulose in NMMO with the addition of

**Figure 32.** Schematic representation of the structure evolution during spinning of composite fibers

**6. Fibrillization and mechanical properties of cellulose and synthetic polymers and layered aluminosilicates micro- and nanocomposite fibers**

The following structure peculiarity of the process under discussion was found. This is the formation of mesamorphic matrix cellulose phase due to introducing synthetic polymers or

decomposition of the system and, correspondingly, is at equilibrium.

So, it has been shown that the introduction of copolyester, PMPIA and clays into cellulose solutions in NMMO makes it possible to govern the processes of the cellulose structuring and to finish them on the stage of the 2*D* mesophase formation and, thus, to avoid further perfection of the structure and the formation of the crystalline phase of cellulose. In other words, the structural situation is the same as in the case of the as-spun cellulose fibers. The only difference is that, in purely cellulose fibers, the resulting mesophase is not at equilibrium, while in blend systems, the 2*D* mesophase forms after the complete phase

**Figure 33.** Micrographs of cellulose (a) and mixed fibers: cellulose/PMPIA (b) and cellulose/M2CloisiteNa+(c) before and after mechanical treatment in a vibrating mill in the aquatic environment (diameter of the fibers is 14-16 m).

The obtained micro- and nanocomposite fiber cellulose/CPE (PMPIA) and cellulose/clay have high mechanical properties, which by 1.5–3 times exceed the strength properties of cellulose fibers (Table1). At the same time, the deformation parameters of composite fibers are not reduced, and, in some cases, are substantially increased in comparison with the standard cellulose fibers.

**Table 1.** Mechanical properties of micro- and nanocomposites

## **7. Conclusion**

A method for the preparation of solid-phase compositions of cellulose with synthetic polymers and layered aluminosilicates Cloisite Na+ and Cloisite 20А has been developed. It provides high dispersion and uniform distribution of a polymer or micro- and clay nanoparticles in the matrix cellulose phase.

The addition of polymers and clay to cellulose solutions in NMMO, regardless of the nature of a polymer as well as phase and/or structure peculiarities of mixed solutions, allows us to control the process of structurization of the matrix cellulose phase, leading it to the formation of 2D mesophase, thereby excluding a possibility of crystallization.

Novel nanostructures composed of cellulose/clay and cellulose/polymer fibers possess high mechanical properties: their strength and modulus are 1,5–2 times higher than those of cellulose.

Our studies have made it possible to approach the solution of an extremely important issue that consists in the regulation of the cellulose structuring. Until now this did not have any direct solution. Thus, it becomes possible to manufacture cellulose-based fibers that have the desired combination of characteristics.

## **Author details**

Ludmila Golova, Igor Makarov, Ludmila Kuznetsova, Elena Plotnikova and Valery Kulichikhin *A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia*

### **8. References**

[8] Golova L. K., Makarov I. S., Matukhina E. V., Kuptsov S. A., Shambilova G. K. and Kulichikhin V. G. Crystal Solvates of Thermotropic Alkylenearomatic Copolyesters and Poly(*m*-phenyleneisophthalamide) with *N*-Methylmorpholine-*N*-oxide . Vysokomol.Soedin 2008; A (50) 665 – 678.

340 Cellulose – Fundamental Aspects

nanoparticles in the matrix cellulose phase.

desired combination of characteristics.

Elena Plotnikova and Valery Kulichikhin

Symposium 1983; 37 239-259.

Lenzinger Bericht 1996; 7 51-63.

[6] Golova L. K. 1992, Russia Patent, No. 1645308

solutions". Khim. Volokna 1996; 1 13-21.

Ludmila Golova, Igor Makarov, Ludmila Kuznetsova,

[1] Franks N. F. and Varga J. K. 1979, US Patent, No. 4290815

A method for the preparation of solid-phase compositions of cellulose with synthetic polymers and layered aluminosilicates Cloisite Na+ and Cloisite 20А has been developed. It provides high dispersion and uniform distribution of a polymer or micro- and clay

The addition of polymers and clay to cellulose solutions in NMMO, regardless of the nature of a polymer as well as phase and/or structure peculiarities of mixed solutions, allows us to control the process of structurization of the matrix cellulose phase, leading it to the

Novel nanostructures composed of cellulose/clay and cellulose/polymer fibers possess high mechanical properties: their strength and modulus are 1,5–2 times higher than those of

Our studies have made it possible to approach the solution of an extremely important issue that consists in the regulation of the cellulose structuring. Until now this did not have any direct solution. Thus, it becomes possible to manufacture cellulose-based fibers that have the

*A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia*

[2] Chanzy H., Noe P., Paillet M., Smith P. Swelling and dissolution of cellulose in amine oxide/water systems. Journal of Applied Polymer Science: Applied Polymer

[3] Kruger R. Cellulosic filament yarn from the NMMO process. Lenzinger Berichte 1994; 4

[4] Golova L. K., Kulichikhin V. G., and Papkov S. P. Mexanism of dissolution of cellulose

[5] Cousey H. A., Smith S.B. The Formation and Structure of a new Cellulose Fibre.

[7] Golova L. K. A new method of processing cellulose via highly concentrated "solid

in nonaqueous solvents. Vysokomol. Soedin 1986; A(28) 1795-2016.

formation of 2D mesophase, thereby excluding a possibility of crystallization.

**7. Conclusion**

cellulose.

**Author details**

**8. References**

49-52.

	- [22] Makarov I.S., Golova L.K., Rebrov A.V., Matukhina E.V., Kulichikhin V.G. Biodegrable nanocomposites based on cellulose with Na-montmorillonite. AERC 2011. 7th Annual European Rheology Conference .Suzdal - Russia; 2011.

## **Cellulose Nanofibers and Its Applications for Resin Reinforcements**

Mariko Yoshioka, Yoshiyuki Nishio, Satoru Nakamura, Yoshiyuki Kushizaki, Ryo Ishiguro, Toshiki Kabutomori, Takeo Imanishi and Nobuo Shiraishi

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/55346

## **1. Introduction**

342 Cellulose – Fundamental Aspects

[22] Makarov I.S., Golova L.K., Rebrov A.V., Matukhina E.V., Kulichikhin V.G. Biodegrable nanocomposites based on cellulose with Na-montmorillonite. AERC 2011. 7th Annual

European Rheology Conference .Suzdal - Russia; 2011.

It is widely recognized that technologies that can convert biomass resources into commercially viable materials are needed. Cellulose is a candidate among biomass due to its abundance in nature. The characteristics of cellulose, which include no thermoplasticity and being insoluble in ordinary solvents, have limited its applications. With the aim of widening its application possibilities, several works have been documented on mechanochemical treatments of cellulose in the dry state and in the wet states.[1-6] Endo et al. [1-4] developed novel cellulose composites by ball milling mixtures of cellulose and poly(ethylene glycol) (PEG). The composites are reported to have formed by insertion of PEG molecules among the cellulose molecular chains. [3,4]

Works of Kondo et al*.* [5] and ours [7] appeared as patent publications. In the former case, fine cellulose powder (average powder length and width: 28 and 11 μm, respectively) was pulverized in aqueous suspension by counter collision at a pressure of 200 MPa, being done once or repeatedly up to 60 times or more, using an ultra high-pressure homogenizer, Star Burst System HJP-25005( Sugino Machine Ltd.). In our case [7], cellulose micronized powder (KC flock W-400G, average particle size 24 μm) was used in the same way at a pressure of 245 MPa, being done once or repeatedly up to ten times, using a Star Burst System HJP-25080. These patents appeared independently within the period of 13 months. Kondo et al*.*  [5,6] claimed that pulverization by an ultra high counter collision successfully decomposed the interaction within the assembly structures of cellulose molecules without any damage of the molecular structure, and finally liberated the components into various sizes in water to provide a transparent and homogeneous component-water system after repeated treatments (60 times). While having some claims in common with those of Kondo et al., [5] our work [7] concentrated more on utilization of the ultra high-pressure counter collisiontreated cellulose.

© 2012 Yoshioka et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Yoshioka et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

In fact, our research interests were stimulated by the works of Endo et al., [1-4] and we started to research suitable methods for efficient wet mechanochemical treatment of biomass. Works were performed with the intention of determining pretreatment methods for successive efficient chemical reactions for cellulose in water. The scope of our preliminary works included using a planetary ball mill (Fritch Japan Co.,Ltd.), a bead mill (Ashizawa Finetech Ltd.), a vibration mill (Chuo Kakoki Co.,Ltd.) as well as ultra highpressure homogenizers. The last of these, the Star Burst System HJP-25080 (Sugino Machine Ltd.) [7], was found to be the most effective and acceptable for successive chemical reaction in water.

It can be said that this counter-collision treatment at ultra high pressure is an extension of the microfibrillation of cellulose done by ITT Rayonier research group, in which dilute slurries of cellulose fibers were subjected to the repeated mechanical actions of "homogenizing" machine (Gaulin) [8,9]. The slurry was pumped at high pressure and fed through a spring-loaded valve assembly [8]. The aqueous cellulose slurry was pumped at 0.5-5 l/min. The operation pressure was 55 MPa, which is 20%-25% of those for the Star Burst System models.

Because cellulose is composed of aggregated micron-sized microfibrils within the cellulose fiber, the above finding suggests that the cellulose fibers were rapidly expanded in the surface area and grew into their substructural microfibrils by mechanical action and heat. Cellulose nanofiber (CNF) formation or its primordials is considered to be attained.

Starting from these fabricating cellulose nanofibers, authors have been conducting trials for developing related biomass composites. This review chapter addresses some of our findings, which are reported in the three following sections, each having their own experimental section and results and discussion section.

## **2. Fabricating cellulose nanofibers through ultrahigh pressure (245 MPa) counter collision treatments**

As described in the above introduction section, Kondo et al. [5] and authors [7] found a method for fabricating cellulose nanofiber through ultrahigh pressure (200 or 245 MPa) counter collision treatments of cellulose powders in an aqueous slurry state. In our case, the morphologic features of the obtained cellulose nanofiber (CNF) were explored by use of freeze–drying technique and SEM observations. Obtained nanofiber are tend to cohere by themselves during the melt-blending with thermoplastic polymers, oligomers or prepolymers. Thus, the blending or fabricating methods have been explored on the one hand, and chemical modification of starting cellulose in order to prevent the agglomeration of the CNF on the other hand. The chemical modification can place restraint on the inducement of self-assembly of CNF by steric hinderance, electrostatic repulsion and so forth. A recent finding was that the species of the cellulose affects a lot for this fabrication of the nanofiber. These obtained features of CNF are discussed first.

#### **2.1. Experimental**

#### *2.1.1. Materials*

344 Cellulose – Fundamental Aspects

chemical reaction in water.

Burst System models.

In fact, our research interests were stimulated by the works of Endo et al., [1-4] and we started to research suitable methods for efficient wet mechanochemical treatment of biomass. Works were performed with the intention of determining pretreatment methods for successive efficient chemical reactions for cellulose in water. The scope of our preliminary works included using a planetary ball mill (Fritch Japan Co.,Ltd.), a bead mill (Ashizawa Finetech Ltd.), a vibration mill (Chuo Kakoki Co.,Ltd.) as well as ultra highpressure homogenizers. The last of these, the Star Burst System HJP-25080 (Sugino Machine Ltd.) [7], was found to be the most effective and acceptable for successive

It can be said that this counter-collision treatment at ultra high pressure is an extension of the microfibrillation of cellulose done by ITT Rayonier research group, in which dilute slurries of cellulose fibers were subjected to the repeated mechanical actions of "homogenizing" machine (Gaulin) [8,9]. The slurry was pumped at high pressure and fed through a spring-loaded valve assembly [8]. The aqueous cellulose slurry was pumped at 0.5-5 l/min. The operation pressure was 55 MPa, which is 20%-25% of those for the Star

Because cellulose is composed of aggregated micron-sized microfibrils within the cellulose fiber, the above finding suggests that the cellulose fibers were rapidly expanded in the surface area and grew into their substructural microfibrils by mechanical action and heat.

Starting from these fabricating cellulose nanofibers, authors have been conducting trials for developing related biomass composites. This review chapter addresses some of our findings, which are reported in the three following sections, each having their own

**2. Fabricating cellulose nanofibers through ultrahigh pressure (245 MPa)**

As described in the above introduction section, Kondo et al. [5] and authors [7] found a method for fabricating cellulose nanofiber through ultrahigh pressure (200 or 245 MPa) counter collision treatments of cellulose powders in an aqueous slurry state. In our case, the morphologic features of the obtained cellulose nanofiber (CNF) were explored by use of freeze–drying technique and SEM observations. Obtained nanofiber are tend to cohere by themselves during the melt-blending with thermoplastic polymers, oligomers or prepolymers. Thus, the blending or fabricating methods have been explored on the one hand, and chemical modification of starting cellulose in order to prevent the agglomeration of the CNF on the other hand. The chemical modification can place restraint on the inducement of self-assembly of CNF by steric hinderance, electrostatic repulsion and so forth. A recent finding was that the species of the cellulose affects a lot for this fabrication of

Cellulose nanofiber (CNF) formation or its primordials is considered to be attained.

experimental section and results and discussion section.

the nanofiber. These obtained features of CNF are discussed first.

**counter collision treatments**

Micronized cellulose powder (KC flock W-400G, average particle size: 24 μm) was supplied by Nippon Paper Chemicals. "Avicel", Crystalline Cellulose was from Asahi Kasei Co. Deionized water was used throughout, including in suspension of sample powders.

#### *2.1.2. Methods*

#### *Micropulverization of cellulose powders*

Approximately 500 g of cellulose micronized powder was suspended in 20 times weight of deionized water assisted by a powerful stirring device and placed in the feed tank of the Star Burst HJP-25080 ( Sugino Machine Ltd.), which was used for slurry jet counter collision. The aqueous cellulose slurry from the feed tank was divided into two flow channels, which were then pressurized to 245 MPa and are instantaneously injected from small nozzles at high speed. This allowed each fluid stream to collide in the chamber where they combined. The machine automatically permits repeated ultra high-pressure counter-collision treatments and our samples received one to ten collisions (passes).

#### *Characterization*

#### *Scanning electron microscopy*

Morphologies of the untreated cellulose as well as the freeze-dried cellulose, before and after the counter-collision treatment, were observed using a JSM-T330A (JEOL) scanning electron microscope. The samples were mounted on brass stubs and were coated with a thin layer of gold using an ion sputter coater. The freeze-drying treatment was applied for the aqueous cellulose suspensions as well as those obtained through solvent exchange described hereafter. Four freeze-drying methods were performed.

*Regular freeze drying 1.* Aqueous slurry of the cellulosic sample was placed in a glass bottle and placed in a conventional freeze drier (EYELA FD-550; Tokyo Rikakikai), cooled at - 30°C and subjected to freeze drying.

*Regular freeze drying 2*. Aqueous slurry of the cellulosic sample was placed in a glass bottle and was frozen by immersing the bottle in liquid nitrogen. The sample was then subjected to conventional freeze drying.

*Solvent exchange freeze drying.* Imbibed water of cellulose aqueous slurry was exchanged to methanol and then to benzene or *t*-butyl alcohol, with several changes of each solvent. The gel containing benzene or *t*-butyl alcohol was subjected to regular freeze drying 2 as described above.

*Rapid freeze drying.* Imbibed water of cellulose aqueous slurry was exchanged to methanol and then to *t*-butyl alcohol, with several changes of each solvent. Several drops of the *t*-butyl alcohol-containing gel were put directly into liquid nitrogen stored within a dewar vessel and then subjected to the conventional freeze drying as above.

### **2.2. Results and discussion**

At first, a planetary ball mill, a bead mill, and an ultra high-pressure homogenizer were all tried to be used to convert cellulose suspension into an appropriate nanopulverized state. The ultra high-pressure homogenizer was found to be the most suitable, because it can offer increased efficiency and flexibility over the others. In particular, the ultra high-pressure homogenizer offered the most straightforward means and ease of handling in separating the sample from the treating medium (balls, beads). The problems due to contamination of the treated sample with impurities derived from the medium can be avoided, and treatment of larger amounts of samples is possible within a shorter period of time. In this study, Star-Burst HJP-25080 was used as the ultra-high pressure homogenizer.

The additional feature of this ultra high-pressure homogenizer treatment is that the treated cellulose fiber can be homogeneously dispersed in water for a prolonged period. [5, 7] It is considered that cellulose fibers can be pulverized heavily to enlarge its specific surface area to give a much more highly hydrated state than that achieved with untreated cellulosic fiber. To visualize micropulverized states of the counter collision-pretreated cellulose, the morphological structure was studied by SEM as a function of drying method.

Figure 1 shows a SEM photograph of the counter-collision treated cellulose dried by the regular freeze drying 1 method in comparison with that of untreated cellulose. The Star Burst treated cellulose (Fig. 1b) is observed to have surface morphological features different from the untreated cellulose (Fig. 1a). The former has a fibrous surface when compared with the latter, but much of the surface area is severely coagulated to form aggregate structures. It is widely accepted that the relatively slow freezing process causes the formation of ice crystals and squeezes out cellulose microfibrils to form the aggregate structure. The growth of ice crystal on freezing is considered to be prevented by rapid cooling [10]. To confirm the descriptive validity, an SEM photograph was taken of the counter collision-treated cellulose dried by regular freeze drying 2 method (Fig.2).

**Figure 1. a, b.** Scanning electron microscopy (SEM) photographs of cellulose fibers before (a) and after (b) Star Burst treatment (10 passes) followed by the regular freeze drying 1. KC flock W-400G was used as the cellulose sample.

**2.2. Results and discussion**

At first, a planetary ball mill, a bead mill, and an ultra high-pressure homogenizer were all tried to be used to convert cellulose suspension into an appropriate nanopulverized state. The ultra high-pressure homogenizer was found to be the most suitable, because it can offer increased efficiency and flexibility over the others. In particular, the ultra high-pressure homogenizer offered the most straightforward means and ease of handling in separating the sample from the treating medium (balls, beads). The problems due to contamination of the treated sample with impurities derived from the medium can be avoided, and treatment of larger amounts of samples is possible within a shorter period of time. In this study, Star-

The additional feature of this ultra high-pressure homogenizer treatment is that the treated cellulose fiber can be homogeneously dispersed in water for a prolonged period. [5, 7] It is considered that cellulose fibers can be pulverized heavily to enlarge its specific surface area to give a much more highly hydrated state than that achieved with untreated cellulosic fiber. To visualize micropulverized states of the counter collision-pretreated cellulose, the

Figure 1 shows a SEM photograph of the counter-collision treated cellulose dried by the regular freeze drying 1 method in comparison with that of untreated cellulose. The Star Burst treated cellulose (Fig. 1b) is observed to have surface morphological features different from the untreated cellulose (Fig. 1a). The former has a fibrous surface when compared with the latter, but much of the surface area is severely coagulated to form aggregate structures. It is widely accepted that the relatively slow freezing process causes the formation of ice crystals and squeezes out cellulose microfibrils to form the aggregate structure. The growth of ice crystal on freezing is considered to be prevented by rapid cooling [10]. To confirm the descriptive validity, an SEM photograph was taken of the counter collision-treated cellulose

**Figure 1. a, b.** Scanning electron microscopy (SEM) photographs of cellulose fibers before (a) and after (b) Star Burst treatment (10 passes) followed by the regular freeze drying 1. KC flock W-400G was used

Burst HJP-25080 was used as the ultra-high pressure homogenizer.

dried by regular freeze drying 2 method (Fig.2).

as the cellulose sample.

morphological structure was studied by SEM as a function of drying method.

From Fig. 2, the Star Burst treated cellulose is observed to have surface morphological features more significantly different from that for the untreated cellulose (Fig. 1a). It loses the severe aggregate structure of Fig. 1b, but the whole surface is still regularly coagulated to form a laminate layer of thin leaves. Each thin leaf appears to be lamellae composed of cellulose microfibrils.

It is also known that preservation of cellulose fibrillar morphology is better achieved by solvent-exchange freeze drying using methanol and benzene or *t-*butyl alcohol [10]. Thus, it was planned that an additional solvent-exchange experiment was conducted. And, in addition to it, in order to accelerate the freezing process and to hinder ice crystal formation, rapid freeze drying was employed. To this end, drops of the exchanged slurry were directly put into liquid nitrogen stored in a dewar vessel after the solvent exchanges of water methanol-*t-*butyl alcohol, and then subjected to the rapid freeze drying.

The resultant SEM photograph is shown in Figs. 3 and 4. When compared with the image in Fig. 2, it is clear that each thin leaf of cellulose fibrillar lamellae exists separately from others in these figures, noting that thin lamellae (leaves) are stuck to each other and produce laminated materials in the image in Fig. 2. This ease of coalescence among the thin leaves is caused by the easy formation of hydrogen bonding among the hydroxyl groups present on the different surfaces. That is, the thin leaves of cellulose fibrils have high density of –OH groups on the surface, which have a tendency to form hydrogen bonds between hydroxyl groups of adjacent molecules belonging to another thin leaf of cellulose fibrils.

Although the most desirable freeze-drying conditions for this experiment were employed, fibrous microfibrillated cellulose could not be directly obtained. As the ways of dealing with this problem, authors experimented with three investigations.

The first investigation was charging additional agitations for converting the thin leaves of cellulose fibrils into nanofibers. It was started from magnetic stirring during the solventexchange process before the freeze-drying. That is, cellulose slurry was pulverized by counter collision at a pressure of 245 MPa, after which the pulverized product was solventexchanged followed by freeze-drying. In the experiment, benzene was used as the final solvent of the solvent-exchange process and mechanical agitation was used during the solvent-exchange process. The SEM photograph of the corresponding freeze-dried product is shown in Fig. 5.

**Figure 3.** SEM photograph of cellulose fibers after Star Burst treatment (10 passes) followed by solvent exchange and rapid freeze drying.

No. 114, ×40,000 No. 115 ×20,000

**Figure 4.** Other examples of SEM photographs of cellulose fibers after Star Burst treatment (10 passes) followed by solvent exchange and rapid freeze drying.

Figure 5 shows that a large number of cellulose fibers are yielded on or near the surface but lamellae-like structures are observed behind. The cellulose fibers can be recognized as a nanofiber when taking the thickness (ca. 38nm) of the gold coating into consideration. Thus, it may be argued that although the untreated cellulose fibers with diameters of 8-20μm were pulverized to diameters of several nanometers, the formation of nanofibers was limited and incomplete (Fig. 5). This is despite the fact that the cellulose received the ultra high-pressure homogenizing treatment and stirrer agitation during the solvent-exchange process. When comparing the results of Figs. 2 and 5, however, it can be said that the magnetic-stirrer agitation having continued two days resulted in an insufficient formation of cellulose nanofiber.

348 Cellulose – Fundamental Aspects

is shown in Fig. 5.

exchange and rapid freeze drying.

solvent of the solvent-exchange process and mechanical agitation was used during the solvent-exchange process. The SEM photograph of the corresponding freeze-dried product

**Figure 3.** SEM photograph of cellulose fibers after Star Burst treatment (10 passes) followed by solvent

No. 112, ×40,000 No. 113 ×33,000

No. 114, ×40,000 No. 115 ×20,000 **Figure 4.** Other examples of SEM photographs of cellulose fibers after Star Burst treatment (10 passes)

followed by solvent exchange and rapid freeze drying.

Then, the degree of mechanical stimulations used for post-processing of the countercollision were tried to be strengthened by use of T. K. ROBOMIX® (PRIMIX Co.), or by an ultrasonic processor (Sharp Co.; UT-205HS). An aggressive stirring with the rate of 15,000 rpm for 60 min was used by the former, and a treatment for 60 min at 40 kHz was taken for the latter.

After these treatments, both aqueous slurries were rapidly freeze dryed and SEM photograph were taken. As shown in Fig. 6, developments of CNF were clearly advanced, but even after these post-treatments, thin leaf structures of cellulose lamellae are still partially remaining. Effect of the treatment with T. K. ROBOMIX became larger compared with that with the ultrasonic processor [11].

It is considered that strong agitation followed by adept kneading with twin-screw extruder, would break the thin leaf structure of cellulose fibrillar lamellae, yielding nanofibrous microfibrillated cellulose. To examine this point, several experiments were performed and results are shown in the third section of this article.

The second investigation was to use half-esterified cellulose of dibasic acid anhydride (e.g. maleic anhydride) for the ultra high-pressure homogenizer treatment. By introducing small

amounts (1~5wt%) of the half- esters on the amorphous region and microfibril surface of cellulose, followed by the counter collosion treatment, electrostatic repulsion and steric hinderance effects rose up and a rather well formation of nano-fibers was caused as shown in Fig. 7. It is understandable from this figure that the degree of conversion to nano-fiber is advanced.

**Figure 6.** SEM photograph of KC flock W-400G after Star Burst treatment (10 passes) followed by an aggressive stirring with the rate of 15,000 rpm for 60 min (left), or by ultrasonic processor treatment (40 kHz) (right), and further followed by rapid freeze drying.

**Figure 7.** SEM photograph of half- esterified cellulose fibers after Star Burst treatment (10 passes) followed by rapid freeze drying.

The third investigation was to choose the species of cellulose. There are big differences in the nanofiber formation behavior between KC flock W-400G micronized cellulose powder and "Avicel", crystalline cellulose. Conversion to nano-fiber is easier for the latter when compared with the former. Even in non-treated state there are obvious differences between them as shown in Fig. 8. In Avicel's case, fibers are clearly observable and in KC flock W-400G's case, fibers are buried much more within the matrix binders.

On the other hand, however, when Avicel was used, nano-fiber formation was accomplished through 5 min of an aggressive post stirring with the rate of 15,000 rpm after the Star Burst treatment gave the tremendous effect in this cellulose species (Fig. 9). The results shown in Figs. 8 and 9, and also 6 reveals the big difference caused by selection of cellulose species.

350 Cellulose – Fundamental Aspects

advanced.

amounts (1~5wt%) of the half- esters on the amorphous region and microfibril surface of cellulose, followed by the counter collosion treatment, electrostatic repulsion and steric hinderance effects rose up and a rather well formation of nano-fibers was caused as shown in Fig. 7. It is understandable from this figure that the degree of conversion to nano-fiber is

**Figure 6.** SEM photograph of KC flock W-400G after Star Burst treatment (10 passes) followed by an aggressive stirring with the rate of 15,000 rpm for 60 min (left), or by ultrasonic processor treatment (40

**Figure 7.** SEM photograph of half- esterified cellulose fibers after Star Burst treatment (10 passes)

400G's case, fibers are buried much more within the matrix binders.

The third investigation was to choose the species of cellulose. There are big differences in the nanofiber formation behavior between KC flock W-400G micronized cellulose powder and "Avicel", crystalline cellulose. Conversion to nano-fiber is easier for the latter when compared with the former. Even in non-treated state there are obvious differences between them as shown in Fig. 8. In Avicel's case, fibers are clearly observable and in KC flock W-

kHz) (right), and further followed by rapid freeze drying.

followed by rapid freeze drying.

**Figure 8.** SEM photographs of the surfaces of untreated KC flock W-400G (right) and "Avicel"(left) powders.

**Figure 9.** SEM photograph of Avicel after Star Burst treatment (10 passes) followed by an aggressive stirring with T. K. ROBOMIX (stirring rate of 15,000 rpm for 5 min) and by rapid freeze drying.

Percentage amounts of nano-cellulose fiber composited to matrix resins have been an another problem. In general, investigators and scientists are tried to employ the values of 10% or more. At first, they used higher CNF concentration of 50~90 % in the corresponding composites.

On the other hand, there are arguments claiming that the smaller the particle, the smaller the clearance of the particle in particle/matrix resin composites, when the particle concentration is constant [12]. Nano-particles are those having near the smallest in dimension which cause their particle clearances the smallest. Being influenced by these arguments, authors have made choice of the concentration of CNF small, that is, less than 1 wt%. In this regard, 0.05 % Avicel nano-fiber aqueous slurry was prepared and its SEM images were taken after the rapid freeze drying (Fig. 10). The nano-fiber preparation was as follows: an aqueous mixture of Avicel fine powders having Avicel concentration of 0.05% was prepared, treated with Star Burst at 245 MPa counter collision (10 passes), followed by an aggressive stirring with T. K. ROBOMIX (stirring rate of 15,000 rpm for 5 min) and by rapid freeze drying. It is known from this figure that, though the slurry concentration is as low as 0.05 % , nano-fibers are indicating a closely-arranged morphology responsible for network structures [11]. That is, a crowded three dimensional network structure is shown.

It is known that CNF formation is much more attained when compared with Figs. 6, 7 and 10. This means again that choice of Avicel instead of KC flock W-400G makes the nano-fiber formation much easier.

**Figure 10.** SEM photograph of the rapid freeze dryed 0.05% Avicel nano-fiber aqueous slurry. The sample was made from 0.05 wt % Avicel aqueous mixture after Star Burst treatment (10 passes) followed by an aggressive stirring with T. K. ROBOMIX (stirring rate of 15,000 rpm for 5 min) and by rapid freeze drying.

## **3. Usage of pulverized cellulosics prepared by ultra high-pressure water jet treatment in polymer nanocomposites**

Using the resultant micropulverized cellulose emulsion prepared from KC flock W-400G, we attempted compositing with vinyl polymers through kneading and evaluated the effects of the counter-collision treatment. Use of KC flock W-400G has been known to result in less than perfect formation of CNF, however, adept kneading with twin-screw extruder was expected to break the thin leaf structure of cellulose fibrillar lamellae, yielding CNF, in the previous chapter. This point will be discussed in this chapter. This newly developed approach offers new opportunities for creating innovative products derived from biomass.

## **3.1. Experimental**

#### *3.1.1. Materials*

352 Cellulose – Fundamental Aspects

formation much easier.

rapid freeze drying.

**jet treatment in polymer nanocomposites**

wt%. In this regard, 0.05 % Avicel nano-fiber aqueous slurry was prepared and its SEM images were taken after the rapid freeze drying (Fig. 10). The nano-fiber preparation was as follows: an aqueous mixture of Avicel fine powders having Avicel concentration of 0.05% was prepared, treated with Star Burst at 245 MPa counter collision (10 passes), followed by an aggressive stirring with T. K. ROBOMIX (stirring rate of 15,000 rpm for 5 min) and by rapid freeze drying. It is known from this figure that, though the slurry concentration is as low as 0.05 % , nano-fibers are indicating a closely-arranged morphology responsible for network structures [11]. That is, a crowded three dimensional network structure is shown.

It is known that CNF formation is much more attained when compared with Figs. 6, 7 and 10. This means again that choice of Avicel instead of KC flock W-400G makes the nano-fiber

**Figure 10.** SEM photograph of the rapid freeze dryed 0.05% Avicel nano-fiber aqueous slurry. The sample was made from 0.05 wt % Avicel aqueous mixture after Star Burst treatment (10 passes) followed by an aggressive stirring with T. K. ROBOMIX (stirring rate of 15,000 rpm for 5 min) and by

**3. Usage of pulverized cellulosics prepared by ultra high-pressure water**

Using the resultant micropulverized cellulose emulsion prepared from KC flock W-400G, we attempted compositing with vinyl polymers through kneading and evaluated the effects of the counter-collision treatment. Use of KC flock W-400G has been known to result in less than perfect formation of CNF, however, adept kneading with twin-screw extruder was expected to break the thin leaf structure of cellulose fibrillar lamellae, yielding CNF, in the previous chapter. This point will be discussed in this chapter. This newly developed approach offers new opportunities for creating innovative products derived from biomass.

Micronized cellulose powder (KC flock W-400G, average particle size: 24 μm) was supplied by Nippon Paper Chemicals. Deionized water was used throughout, including in suspension of sample powders. Agri-wood pellets, rice-type(BIOPOLY JOETSU Co.,Ltd.) including, Agri-wood(R)\_1, Agri-wood(R)\_2 (advanced second-generation) and Agriwood(R)\_3 (advanced third-generation), as well as their inflation-molded sheets were used. Both of Agri-wood(R)\_2 and 3 are composed of old stockpiled rice (rice stored for almost 10 years since harvest), Wintec polyolefin WSX02 (polypropylene random copolymer; Japan Polypropylene), ultra high-pressure counter collision-pretreated cellulose aqueous slurry, and additives, in which the cellulose nanofiber concentration is around 0.05% (w/w). In the cases of Agri-wood(R)\_2 and Agri-wood(R)\_3 pellets, the ultra high-pressure counter collision-pretreated cellulosic slurry at around 0.05% nanofiber concentration was kneaded with Wintec polyolefin WSX02 (polypropylene random copolymer; Japan Polypropylene) and above mentioned old stockpiled rice in the presence of small amounts of additives, using a super high-torque twin-screw extruder (Supertex 77α, The Japan Steel Works), under a controlled moisture vapor release. In the case of Agri-wood(R)\_1, the aqueous cellulose nanofiber slurry was not combined. Inflation-molded bags have been produced commercially from Agri-wood(R)\_2 and 3 and widely used as municipal governmentapproved garbage bags. For our work, these garbage bag sheets were taken as test pieces. Recycled polyethylene (PE) was supplied by Ecos Factory.

#### *3.1.2. Methods*

#### *Micropulverization of cellulose powders*

The method for micropulverization of cellulose powders is the same that taken in the previous chapter.

#### *Preparation of test pieces from inflation-molded bags of Agri-wood(R) pellets for tensile testing*

Inflation molded bags were prepared using a blown film machine (Placo) from Agriwood(R)\_2 and Agri-wood(R)\_3 pellets as well as first-generation Agri-wood(R) \_1 pellets (not combined with cellulose nanofiber) as a control. Sample strips measuring 100×5×0.4 mm were cut from the molded sheets.

#### *Preparation of test pieces of Agri-wood(R) pellets for tensile testing*

Agri-wood(R)\_1~(R)\_3 pellets were molded into sheets at a prescribed temperature by hot pressing using a Toyo-Seiki 10 tons bench hot press. Each sample (approximately 3 g) was placed between polyethylene terephthalate (PET) sheets with a 0.4 mm-thick spacer. For molding, a gauge pressure ranging from 0 to 5 MPa was applied slowly over 3-5 min to allow air bubbles to dissipate. The pressure was subsequently raised to 15 MPa quickly and maintained there for 30 s. The samples were cooled for 10-15 min to room temperature by cold pressing under the same pressure. Sample strips measuring 80×5×0.4mm were cut from

the molded sheets. Agri-wood(R)\_1~(R)\_3 pellets were directly subjected to the measurement of melt index (MI) [melt-flow rate (MFR)].

#### *Compounding micropulverized cellulose with recycled PE*

The ultra high-pressure counter collision-pretreated cellulosic slurry was kneaded with recycled PE at around 0.05 % nanofiber concentration using a super high-torque twin-screw extruder (TEX77α, The Japan Steel Works), under a controlled moisture vapor release. Compounded pellets were obtained from which films were prepared with a blown-film machine (Placo). Recycled PE with or without kneading by the Supertex 77α were used as the controls in the form of films.

#### *Preparation of test pieces of micropulverized cellulose – recycled PE composites for tensile testing*

The test pieces for tensile testing were prepared as described above. The compounded pellets of cellulosic slurry and recycled PE and their control were molded into specimens for the Charpy impact test by use of an Elject NEX110-12E (Nissei Plastic) high-performance injection molding machine.

#### *Characterization*

#### *Scanning electron microscopy*

The method for obtaining SEM photograph is the same that taken in the previous chapter. Fracture cross sections obtained by tensile elongation testing of the inflation-molded sheets prepared from Agri-wood(R)\_2 and 3 were visualized by SEM.

#### *Mesurements of mechanical properties of the Agri-wood(R), and recycled PE composite*

An IM-401 Charpy-type Impact Tester (Tester Sangyo) was used for Charpy impact test, while a Universal Testing Machine AG10kNIS (Shimadzu) was used for tensile testing. Melt flow rate was measured by a Melt Flow Indexer IMC-1540 (Imoto Machinery).

Dynamic viscoelastic measurements were performed for the strips using a Rheogel-E4000 (UBM) under tension mode (frequency 10Hz, rate of temperature increase 3°C/min).

#### **3.2. Results and discussion**

#### *Composite processing*

Inflation films molded from pellets of Agri-wood(R)\_2 and 3 were prepared, their tensile properties were measured, and fracture cross sections obtained were visualized by SEM. Figure 11 shows the SEM photographs for the fracture cross section of Agri-wood(R)\_2 film. It is apparent from the figure that there is a scattering of fine starch of a few μm in diameter. The starch particles are almost completely exposed on the destroyed surface. This means that surface adhesion between the starch particle and the matrix resin, percolated by the microfibrillated cellulose fibers is poor. At the time of kneading, cellulose was added as Star Burst treated cellulose slurry (0.5% w/w) to give a concentration of ca. 0.05% in the pellet.

This kneading technique to prepare Agri-wood(R)\_2 pellets was further advanced recently by modifying kneading conditions. Major improvement efforts have been focused on

354 Cellulose – Fundamental Aspects

the controls in the form of films.

injection molding machine.

*Scanning electron microscopy*

**3.2. Results and discussion**

*Composite processing*

*Characterization*

measurement of melt index (MI) [melt-flow rate (MFR)].

prepared from Agri-wood(R)\_2 and 3 were visualized by SEM.

*Compounding micropulverized cellulose with recycled PE*

the molded sheets. Agri-wood(R)\_1~(R)\_3 pellets were directly subjected to the

The ultra high-pressure counter collision-pretreated cellulosic slurry was kneaded with recycled PE at around 0.05 % nanofiber concentration using a super high-torque twin-screw extruder (TEX77α, The Japan Steel Works), under a controlled moisture vapor release. Compounded pellets were obtained from which films were prepared with a blown-film machine (Placo). Recycled PE with or without kneading by the Supertex 77α were used as

*Preparation of test pieces of micropulverized cellulose – recycled PE composites for tensile testing*

The test pieces for tensile testing were prepared as described above. The compounded pellets of cellulosic slurry and recycled PE and their control were molded into specimens for the Charpy impact test by use of an Elject NEX110-12E (Nissei Plastic) high-performance

The method for obtaining SEM photograph is the same that taken in the previous chapter. Fracture cross sections obtained by tensile elongation testing of the inflation-molded sheets

An IM-401 Charpy-type Impact Tester (Tester Sangyo) was used for Charpy impact test, while a Universal Testing Machine AG10kNIS (Shimadzu) was used for tensile testing. Melt

Dynamic viscoelastic measurements were performed for the strips using a Rheogel-E4000

Inflation films molded from pellets of Agri-wood(R)\_2 and 3 were prepared, their tensile properties were measured, and fracture cross sections obtained were visualized by SEM. Figure 11 shows the SEM photographs for the fracture cross section of Agri-wood(R)\_2 film. It is apparent from the figure that there is a scattering of fine starch of a few μm in diameter. The starch particles are almost completely exposed on the destroyed surface. This means that surface adhesion between the starch particle and the matrix resin, percolated by the microfibrillated cellulose fibers is poor. At the time of kneading, cellulose was added as Star Burst treated cellulose slurry (0.5% w/w) to give a concentration of ca. 0.05% in the pellet.

*Mesurements of mechanical properties of the Agri-wood(R), and recycled PE composite*

flow rate was measured by a Melt Flow Indexer IMC-1540 (Imoto Machinery).

(UBM) under tension mode (frequency 10Hz, rate of temperature increase 3°C/min).

**Figure 11.** SEM photographs of fracture cross section of inflation film molded from Agri-wood(R)\_2 [second-generation Agri-wood(R)] pellets obtained by tensile elongation test.

**Figure 12.** SEM photographs of fracture cross section of inflation film molded from Agri-wood(R)\_3 [third-generation Agri-wood(R)] pellets obtained by tensile elongation test.

techniques of programmed evacuation of water vapor from the vents at pressurized, normal, and reduced pressures, as well as adopting appropriate paddle constructions [13, 14]. Such advancements were actually reflected on the SEM photographs of the fracture cross section of the film molded from Agri-wood(R)\_3 pellets (Fig. 12). The starch particles are almost completely covered by the matrix resin, showing that surface adhesion between the starch particle and the matrix resin, percolated by the microfibrillated cellulose fibers is enhanced and morphological characteristics among these three components became more intimately unified. That is, cellulose nanofibers and starch particles (smaller size than those in Fig. 11) are homogeneously dispersed and combined with the matrix resin. Four photographs corresponding to and confirming Fig. 12 are shown in Fig. 13. The starch particles are also almost completely covered by the matrix resin, and penetrations of microfibrillated cellulose fibers through starch grains as well as matrix resin can be observed. That is, the mechanical interlocking caused by cellulose nanofibers are occurring, though the amounts are quite small. This argument is at least supported by the MFR values shown in Table 1. When comparing the MFR value for sample No. 2 with that for sample No. 3, the latter value is smaller than the former. The melt flowability of the matrix resin, Wintec polyolefin WSX02, is obviously much higher than that of rice starch and the microfibrillated cellulose fibers. It is thus considered that sample No. 2 composite is less blended than the advanced type and contains partly polyolefin rich portions in the composite due to the nonadvanced kneading technique. Therefore, the part of free polyolefin that is not well compatibilized with the rice starch and the microfibrillated cellulose fibers preferably passes through the melt flow indexer die head providing a higher MFR value.

**Figure 13.** SEM photographs of fracture cross section of inflation film molded from Agri-wood(R)\_3 [third-generation Agri-wood(R)] pellets obtained by tensile elongation test as the other examples for Fig. 12.

These observations strongly indicated that cellulose can exist more dispersedly within the nanocomposite after enhanced twin-screw kneading, in which 35%-70% amounts of rice was kneaded with 30%-65% of Wintec polyolefin WSX02 in the presence of small amount of Star Burst treated cellulose slurry. This argument is further enhanced by the results obtained from measuring the solid state properties of the molded test pieces. As shown in Table 1, all the tensile properties were enhanced in the order of the extent of nanofiber reinforcement. Especially, the value of tensile elongation at breakage can reflect the enhancement of compatibilization of the composite components of starch grain, matrix polyolefin, and microfibrillated cellulose fibers.

Concerning these findings, followings are found in the literatures. It can be stated as the first place, that cellulose nanofibers have a high density of hydroxyl groups, facilitating their agglomeration, and reducing interaction with surrounding matrix. Agglomeration is the formation of groups of cellulose fiber due to the hydrogen bonds between each of them. Overcoming strong hydrogen bond requires high energy. The high pressure and high energy in the presence of added water, afforded by the action of a twin-screw extruder were imparted to the cellulose fibers to defibrillate fibrils intensively in achieving acceptable dispersion levels [15].

a 190℃, 10.58 kg

356 Cellulose – Fundamental Aspects

MFR value.

Fig. 12.

polyolefin, and microfibrillated cellulose fibers.

shown in Table 1. When comparing the MFR value for sample No. 2 with that for sample No. 3, the latter value is smaller than the former. The melt flowability of the matrix resin, Wintec polyolefin WSX02, is obviously much higher than that of rice starch and the microfibrillated cellulose fibers. It is thus considered that sample No. 2 composite is less blended than the advanced type and contains partly polyolefin rich portions in the composite due to the nonadvanced kneading technique. Therefore, the part of free polyolefin that is not well compatibilized with the rice starch and the microfibrillated cellulose fibers preferably passes through the melt flow indexer die head providing a higher

**Figure 13.** SEM photographs of fracture cross section of inflation film molded from Agri-wood(R)\_3 [third-generation Agri-wood(R)] pellets obtained by tensile elongation test as the other examples for

These observations strongly indicated that cellulose can exist more dispersedly within the nanocomposite after enhanced twin-screw kneading, in which 35%-70% amounts of rice was kneaded with 30%-65% of Wintec polyolefin WSX02 in the presence of small amount of Star Burst treated cellulose slurry. This argument is further enhanced by the results obtained from measuring the solid state properties of the molded test pieces. As shown in Table 1, all the tensile properties were enhanced in the order of the extent of nanofiber reinforcement. Especially, the value of tensile elongation at breakage can reflect the enhancement of compatibilization of the composite components of starch grain, matrix

Concerning these findings, followings are found in the literatures. It can be stated as the first place, that cellulose nanofibers have a high density of hydroxyl groups, facilitating their agglomeration, and reducing interaction with surrounding matrix. Agglomeration is the b First generation Agri-wood(R); no added cellulose nanofiber; polyolefin / rice = 30 / 70 (w/w)

 c Second generation Agri-wood(R); polyolefin / rice / cellulose nanofiber = 30 / 70 / 0.05 (w/w)

 d Third generation Agri-wood(R); polyolefin / rice / cellulose nanofiber = 30 / 70 / 0.05 (w/w)

**Table 1.** Mechanical properties of a series of Agri-wood(R) samples

The inherent polar and hydrophilic nature of the nanofiber and the non-polar characteristic of most thermoplastics result in difficulties in compounding the filler and the matrix. In view of these, there is a possibility that the presence of starch in the kneading system play a prominent role in achieving acceptable dispersion levels. It is possible that the starch molecule interacts with cellulose nanofibers, covers them and by that improves the dispersion of the cellulose nanofiber. Actually, Oksman *et.al.,* studied a manufacturing process of cellulose whisker / polylactic acid (PLA) nanocomposites and found by TEM observation that dispersed composite structures could be obtained when water-soluble polyethylene glycol (PVA) was included as an additive [16].

Figure 14 shows the storage modulus as a function of temperature for neat polyorefine (Wintec WSX02)(×), the first generation Agri-wood without cellulose nanofiber and the two kinds of Agri-wood/Cellulose nanofiber composites. The latter three are corresponding to Agri-wood(R)\_1~3 in Table 1.

The curve corresponding to the pure matrix (x) shows typical of thermoplastic behavior. The neat polyorefine (Wintec WSX02) is a random copolymer of PP (with small amounts of PE) having a melting temperature of 125 °C. Thus, the starting temperature (room temperature) for the measurement is very close to Tg of the polymer, from which a rapid decrease in the elastic tensile modulus is occurring. Then, a rapid decrease in the elastic tensile modulus, by more than 3 decades, is observed, corresponding to the glass-rubber transition, after which it seems to go directly into flow region but the experimental setup fails to measure it.

The storage modulus in Fig. 14 shows that the three of the Agri-woods have higher moduli on the entire temperature ranges compared to that of the neat polyorefine (Wintec WSX02), which is caused by the starch filler effect. The corresponding data have shown large effect of starch fillers, which is further reinforced by the small coexistence of cellulose nanofibers, in order to obtain composites with good mechanical properties and increased stability at higher temperatures. The contents of cellulose nanofiber are remarkably small (ca.0.05%), its role can hardly be seen in the figure (Fig. 14).

◇: Agri-wood (R) 1st Generation (Control)( no added cellulose nanofiber; polyolefin/rice=30/70(w/w)); △: Agri-wood (R) 2nd Generation ( polyolefin/rice/cellulose nanofiber=30/70/0.05(w/w)); ○: Agri-wood (R) 3rd Generation ( polyolefin/rice/cellulose nanofiber=30/70/0.05(w/w))

**Figure 14.** Temperature dependencies of storage modulus (E') of neat polyorefine (Wintec WSX02) (×) and the Agri-wood/Cellulose nanofiber composites.

The influence of nanofiber existence for enhancing physical properties can be observed in the case of physical blending of microfibrillated cellulose fibers with thermoplastic polymer. An example is shown in Table 2. In this case, recycled PE was used instead of Wintec polyolefin WSX02 and kneaded with a small amount of Star Burst treated cellulose slurry. The resulting physical properties of the molded specimen were significantly improved when compared with the corresponding control, especially for impact strength and tensile elongation at breakage. This showed that nanofibrous microfibrillated cellulose was well dispersed within the molded specimen.

1) 190°C, 10.58 kg

2) Recycled PE / Cellulose nanofiber = 100 / 0.05 (w/w)

**Table 2.** Mechanical properties of the recycled PE / cellulose nanofiber composite

## **4. Usage of pulverized cellulosics prepared by ultra high-pressure water jet treatment in development of separator sheets equipped within the lithium ion battery (A feasibility study)**

As shown in Table 1 in the previous chapter, the tensile properties were enhanced in the order of the additional or advantageous effect of nanofiber reinforcement. And also in Table 2, it was shown that when recycled PE was kneaded with a small amount of aqueous Star Burst treated cellulose slurry, the resulting molded specimens indicated improved physical properties when compared with the corresponding control. It is known, at the same time, that the presence of small amounts of cellulose nanofiber effects an enhancement of the heat resistance of the matrix resin [14]. These data encouraged us to apply these CNF reinforced HDPE to separator sheets equipped within the lithium ion battery.

An utilization of CNF reinforced polyolefin for the separator sheets equipped within the lithium ion battery [17] has been experimenting as a feasibility study. By use of the CNF from KC flock W-400G, half-esterified KC flock W-400G and half-esterified Avicel, the heat resistance and strength properties of the modified polyolefin sheets have been enhanced, which enables the sheets to be used for this purpose. Concerning data obtained up to now will be shown and discussed.

#### **4.1. Experimental**

#### *4.1.1. Materials*

358 Cellulose – Fundamental Aspects

role can hardly be seen in the figure (Fig. 14).

polyolefin/rice/cellulose nanofiber=30/70/0.05(w/w))

dispersed within the molded specimen.

No. Sample Charpy impact

2) Recycled PE / Cellulose nanofiber = 100 / 0.05 (w/w)

**Table 2.** Mechanical properties of the recycled PE / cellulose nanofiber composite

1) 190°C, 10.58 kg

and the Agri-wood/Cellulose nanofiber composites.

which is caused by the starch filler effect. The corresponding data have shown large effect of starch fillers, which is further reinforced by the small coexistence of cellulose nanofibers, in order to obtain composites with good mechanical properties and increased stability at higher temperatures. The contents of cellulose nanofiber are remarkably small (ca.0.05%), its

◇: Agri-wood (R) 1st Generation (Control)( no added cellulose nanofiber; polyolefin/rice=30/70(w/w)); △: Agri-wood (R) 2nd Generation ( polyolefin/rice/cellulose nanofiber=30/70/0.05(w/w)); ○: Agri-wood (R) 3rd Generation (

**Figure 14.** Temperature dependencies of storage modulus (E') of neat polyorefine (Wintec WSX02) (×)

The influence of nanofiber existence for enhancing physical properties can be observed in the case of physical blending of microfibrillated cellulose fibers with thermoplastic polymer. An example is shown in Table 2. In this case, recycled PE was used instead of Wintec polyolefin WSX02 and kneaded with a small amount of Star Burst treated cellulose slurry. The resulting physical properties of the molded specimen were significantly improved when compared with the corresponding control, especially for impact strength and tensile elongation at breakage. This showed that nanofibrous microfibrillated cellulose was well

strength / kJm-2

1 Control 1 (Untreated recycled PE) 29 17 72 17 2 Control 2 (Kneaded recycled PE) 28 14 64 11 3 Cellulose nanofiber composite2) 46 15 300 10

Tensile strenth / MPa

Tensile elongation at break / %

MFR1) / (g/10min) Micronized cellulose powder (KC flock W-400G, average particle size: 24 μm) was supplied by Nippon Paper Chemicals. "Avicel", Crystalline Cellulose was from Asahi Kasei Co. Deionized water was used throughout, including in suspension of sample powders. Succinic anhydride was from nacalai tesque high-density polyethylene (HDPE)("HI-ZEH(HDPE)7000F") was from Mitui Hi-Zex Co. Ltd.

#### *4.1.2. Methods*

#### *Half esterification of cellulose with succinic anhydride*

Half esterification of cellulose powders (KC flock W-400G and Avicel) with succinic anhydride was conducted by use of 500 mL Dispersion Mixer (MS Moriyama Co.). 100 weight parts of cellulose fine powders were mixed and reacted with 5 weight parts of succinic anhydride without solvent at 140°C for 40 min.

#### *Micropulverization of the half esterufied cellulose powders*

0.5 and 5% aqueous slurrys of cellulose or the prepared succinic anhydride half esterified cellulose fine powders were converted to nano-fiber by use of Star Burst mini ( Sugino Machine Ltd.). The method for micropulverization of cellulose powders is the same that token in the previous chapter.

#### *Compounding micropulverized cellulose (CNF) with high-density polyethylene (HDPE)("HI-ZEH (HDPE) 7000F")*

The ultra high-pressure counter collision-pretreated cellulosic or half-esterified cellulosic

slurry(5% and 0.5%) was kneaded with high-density polyethylene (HDPE ("HI-ZEH (HDPE) 7000F") at around 0.5 or 0.05 % nanofiber concentration with or without maleic anhydride modified PP (3%) and lubricant (BYK-P4101(1%)), using a super high-torque twin-screw extruder (Intermeshed co-rotation twin screw extruder (screw diameter= 48 mm, L/D=60), Technovel.Co.), under a controlled moisture vapor release. The compounding was done in the plant of Shiraishi Biomass Co. Ltd., located in Kyoto prefecture. Compounded pellets were obtained as shown in Table 3, from which films were prepared as described later.

\*phr : per hundred resin

**Table 3.** CNF composited HDPE pellets

#### *Preparation of biaxially-drawn porous film made by a phase separation method*

360 Cellulose – Fundamental Aspects

*(HDPE) 7000F")*

later.

Pellet No.

③ HDPE+halfesterified CNF

④ HDPE+halfesterified CNF+ maleic anhydride modified PP

⑤ HDPE+halfesterified CNF

⑥ HDPE+halfesterified CNF

⑦ HDPE+halfesterified CNF+ lubricant

⑧ HDPE+halfesterified CNF+ lubricant

\*phr : per hundred resin

**Table 3.** CNF composited HDPE pellets

*Compounding micropulverized cellulose (CNF) with high-density polyethylene (HDPE)("HI-ZEH*

The ultra high-pressure counter collision-pretreated cellulosic or half-esterified cellulosic slurry(5% and 0.5%) was kneaded with high-density polyethylene (HDPE ("HI-ZEH (HDPE) 7000F") at around 0.5 or 0.05 % nanofiber concentration with or without maleic anhydride modified PP (3%) and lubricant (BYK-P4101(1%)), using a super high-torque twin-screw extruder (Intermeshed co-rotation twin screw extruder (screw diameter= 48 mm, L/D=60), Technovel.Co.), under a controlled moisture vapor release. The compounding was done in the plant of Shiraishi Biomass Co. Ltd., located in Kyoto prefecture. Compounded pellets were obtained as shown in Table 3, from which films were prepared as described

amount

Avicel 0.1phr 20phr 0.5wt% ↑

Slurry input amount

Slurry concentrat ion

only

0.1phr\* 20phr 0.5wt% 10 passes

0.1phr 20phr 0.5wt% ↑

0.5phr 10phr 5wt% ↑

0.1phr 20phr 0.5wt% ↑

0.5phr 10phr 5wt% ↑

Star Burst treating frequency

Composition Cellulose Additive CNFcomposition

① HDPE 0 0

KC flock W400G

KC flock W400G

KC flock W400G

KC flock W400G

KC flock W400G

② HDPE 0 10phr Water

Maleic anhydride modified PP 3%

BYK-P4101 1%

BYK-P4101 1%

Each compounded pellets of micropulverized non-treated or half-esterified cellulose with HDPE ("HI-ZEH (HDPE)7000F") (Table 3) was mixed with liquid paraffin at a weight rate of 6:4, first in a beaker for the swelling of the pellets with liquid paraffin for 30 min, and then by use of a small size mixer at 180°C for 30 min, as shown in Figs. 15 and 16.

**Figure 15.** Swelling of the CNF compounded HDPE pellets with liquid paraffin.

**Figure 16.** The small size mixer used for kneading the pellets with liquid paraffin.

The kneaded products were molded with a metal mold (100mmΦx1mm thickness) at 180℃ under the pressure of 20 MPa. From obtained sheets, square shape sheets with a dimension of 80mm x 80mm were punched out, which were biaxially-stretched simultaneously in 5 x 5 multiples through the use of a table tenter (Fig.17). The stretching temperature was 110℃ and the rate of stretching was 8000 mm/min.

Then, from the prepared biaxially-drawn sheets, liquid paraffin was extracted with methylene chloride, obtaining biaxially-drawn porous films. These operations were done in the plant of The Japan steel works, Ltd., located in Hiroshima prefecture. Then, from the SEM observations and the measurements of air permeability on the biaxially-drawn porous films, the potentiality of the obtained sheets for the application to the separator sheets equipped within the lithium ion battery was discussed.

**Figure 17.** The table tenter used for biaxially-stretching the sheets.

#### *Characterization*

#### *Scanning electron microscopy*

SEM observations were done after extracting liquid paraffin through methylene chloride, trying to obtain biaxially-drawn porous films. SEM photographs 18 and 19 were obtained by FE-SEM(Thermal field emission scanning electron microscope, JSM-7000F)(JEOL), after platinum deposition of ca. 3 nm thickness through the ion sputtering device, Super Fine Coater : ESC-101 (ELIONIX). The FE-SEM photographs were shown at the magnification ratio of 20,000.

#### *Mesurement of air permeability*

Air permeability measured by the Gurley densometer IM38-03-00 (air permeability measuring device; Testing Machines Inc.).

#### **4.2. Results and discussion**

#### *Composite processing*

As described in the experimental section, six kinds of CNF/higher molecular weight HDPE pellets have been prepared (Table 3). Also, as described in the experimental section, an array of biaxially-drawn porous films were finally prepared.

#### *SEM observations of prepaired biaxially-drawn porous films*

The characterful SEM imeges obtained for biaxially-drawn porous films are shown in Figs. 18 and 19, those film of which are prepared from pellet ④ and ⑥ in Table 3, respectively. Fibrous substances in several μm length are dispersed and unlevel pore like patterns are existing. The latter are presumed to be derived from shrinkage of the pores, caused by residual stress, arising from biaxially-stretching or liquid paraffin extraction. In this experiment, the second biaxially-stretching at certain temperature was not performed after the liquid paraffin extraction, which is usually conducted in the correspondent industrial plant. Thus, the shrinkage of the pores, caused by residual stress, would rise up and pore would be obstructed partly. From these observations, it can be said that the samples ④ and ⑥ have evidences of coming with good to excellent pores and are pointed out the possibility of expressing characteristics as separator sheets.

**Figure 18.** SEM photographs of the surfaces of biaxially-drawn porous films prepared from pellet ④ in Table 3. (20,000 magnifications)

**Figure 19.** SEM photographs of the surfaces of biaxially-drawn porous films prepared from pellet ⑥ in Table 3. (20,000 magnifications)

#### *Air permeability of prepaired biaxially-drawn porous films*

362 Cellulose – Fundamental Aspects

*Characterization*

ratio of 20,000.

*Scanning electron microscopy*

*Mesurement of air permeability*

**4.2. Results and discussion**

*Composite processing*

measuring device; Testing Machines Inc.).

of biaxially-drawn porous films were finally prepared. *SEM observations of prepaired biaxially-drawn porous films*

equipped within the lithium ion battery was discussed.

**Figure 17.** The table tenter used for biaxially-stretching the sheets.

SEM observations and the measurements of air permeability on the biaxially-drawn porous films, the potentiality of the obtained sheets for the application to the separator sheets

SEM observations were done after extracting liquid paraffin through methylene chloride, trying to obtain biaxially-drawn porous films. SEM photographs 18 and 19 were obtained by FE-SEM(Thermal field emission scanning electron microscope, JSM-7000F)(JEOL), after platinum deposition of ca. 3 nm thickness through the ion sputtering device, Super Fine Coater : ESC-101 (ELIONIX). The FE-SEM photographs were shown at the magnification

Air permeability measured by the Gurley densometer IM38-03-00 (air permeability

As described in the experimental section, six kinds of CNF/higher molecular weight HDPE pellets have been prepared (Table 3). Also, as described in the experimental section, an array

The characterful SEM imeges obtained for biaxially-drawn porous films are shown in Figs. 18 and 19, those film of which are prepared from pellet ④ and ⑥ in Table 3, respectively. Fibrous substances in several μm length are dispersed and unlevel pore like patterns are Pore volumes and air permeabilities of the biaxially-drawn porous films prepaired from raw material pellets ③~⑧ are shown in Table 4. Pore volumes were derived from thickness and weight of 50 mm square sample sheets. As the density of samples, the density of used HDPE (HI-ZEH (HDPE)7000F), that is, 0.95g/cm3 , was adopted.

Air permeabilities were calculated from the obtained Gurley values, using the formulas shown in the footnote of Table 4.

Sheets prepared from raw material pellets ③ and ④ reviel Gurley values (times required 100ml air passing through the sheet) less than 1000, however, others have the values more than 3000, reflecting the small pore existence rate. Especially, the sheet prepared from raw material pellet ④ exhibits the air permeability value almost equal to that obtained for the standard sample, showing the existence of pass-through pores. The previous SEM observation also pointed out that the sheet prepared from raw material pellet ④ gave the result showing the existence of pass-through pores.

From these data, it can be said that the second biaxially-stretching at certain temperature should be performed after the liquid paraffin extraction. In addition, there is an argument in our research group that as the matrix resin, more appropriate high molecular weight HDPE should be adopted. Under these considerations and others, the related developing studies are continuing.

1) Air permeability:p=135.3/t(time to 100ml permeable), t: Gurley value(s/100cc)

2) Heat stability: Stability during SEM observation.

**Table 4.** Pore volumes and air permeabilities of prepaired biaxially-drawn porous films

## **5. Conclusions**

Cellulose fine powders were found to be effectively pulverized and emulsified by an ultra high-pressure counter collision treatment in an aqueous suspension state. The emulsion was visually stable and did not show any phase separation even after a few years of storage. The fiber diameter of cellulose was reduced from an average of 24 μm to several nanometers by the described treatment. The different effects of different freeze-drying methods were visualized by SEM observations. The coalescence of microfibrillar structures was observed easily when the freeze-drying conditions were inadequate. While the degrees of the microfibrillation done by use of homogenizers including the Star-burst were unsatisfactory for use as fillers for the preparation of polymer nanocomposites, the situation was found to become acceptable one by subsequent after treatment such as using proper kneading techniques. Presence of rice starch or hydrophilic polymers in the CNF and polyolefin kneading system has a big role in improving the dispersion of the CNF in the composite. It is possible that the starch molecule interacts with CNF, covers them and by that improves the dispersion of the CNF. To use half-esterified cellulose of dibasic acid anhydride (e.g. maleic anhydride) enhanced the formation of CNF. By introducing small amounts (1~5wt%) of the half- esters on the microfibril surface of cellulose, followed by the counter collosion treatment, electrostatic repulsion and steric hinderance effects rose up and a rather well formation of nano-fibers was caused. To choose the species of cellulose is one of the factors obtaining a high quality CNF. There are big differences in KC flock W-400G micronized cellulose powder and "Avicel", crystalline cellulose, for example. Conversion to nano-fiber is easier for Avicel when compared with KC flock W-400G. Percentage amounts of nanocellulose fiber combined to matrix resins have been an another key factor. Usually, the values of 10% or more are preferably employed. However, there are arguments claiming that the smaller the particle, the smaller the clearance of the particle in particle/matrix resin composites, when the particle concentration is constant. Nano-particles are those having near the smallest in dimension which cause their particle clearances the smallest. Being influenced by these arguments, authors have made choice of the concentration of CNF less than 1 wt%. It is known that the pysical properties were enhanced by this nanofiber reinforcement and that the presence of small amounts of CNF effects an enhancement of the heat resistance of the matrix resin. As an application study of these CNF reinforced HDPE, preparations of separator sheets for lithium ion battery have been proceeded. From SEM observations, it is known that fibrous substances in several μm length were found to dispers and pores for lithium ion transference could be formed in the biaxially-drawn films prepaired from CNF/HDPE pellets. Further studies are required for this application. Especially, the second biaxially-stretching trials for the separator sheets after the liquid paraffin extraction are required, and HDPE with more adequately high molecular weight should be used. Under these situations and considerations, the developing studies are continuing.

#### **Author details**

364 Cellulose – Fundamental Aspects

are continuing.

Standard sample

**5. Conclusions**

Pellet No. Average

thickness (μm)

2) Heat stability: Stability during SEM observation.

result showing the existence of pass-through pores.

Pore volume (%)

③ 25 21.4 356 0.38

⑤ 27 9.34 >3000 0.05>

⑦ 18 18.1 >3000 0.05>

1) Air permeability:p=135.3/t(time to 100ml permeable), t: Gurley value(s/100cc)

**Table 4.** Pore volumes and air permeabilities of prepaired biaxially-drawn porous films

Sheets prepared from raw material pellets ③ and ④ reviel Gurley values (times required 100ml air passing through the sheet) less than 1000, however, others have the values more than 3000, reflecting the small pore existence rate. Especially, the sheet prepared from raw material pellet ④ exhibits the air permeability value almost equal to that obtained for the standard sample, showing the existence of pass-through pores. The previous SEM observation also pointed out that the sheet prepared from raw material pellet ④ gave the

From these data, it can be said that the second biaxially-stretching at certain temperature should be performed after the liquid paraffin extraction. In addition, there is an argument in our research group that as the matrix resin, more appropriate high molecular weight HDPE should be adopted. Under these considerations and others, the related developing studies

④ 13 33.8 1000 0.14 Accuracy of thickness **:** good

⑥ 44 27.2 > 3000 0.05> Unevenness of thickness **:**

⑧ 24 11.39 >3000 0.05> (high heat stability)2)

Cellulose fine powders were found to be effectively pulverized and emulsified by an ultra high-pressure counter collision treatment in an aqueous suspension state. The emulsion was visually stable and did not show any phase separation even after a few years of storage. The fiber diameter of cellulose was reduced from an average of 24 μm to several nanometers by the described treatment. The different effects of different freeze-drying methods were visualized by SEM observations. The coalescence of microfibrillar structures was observed easily when the freeze-drying conditions were inadequate. While the degrees of the microfibrillation done by use of homogenizers including the Star-burst were unsatisfactory for use as fillers for the preparation of polymer nanocomposites, the situation was found to become acceptable one by subsequent after treatment such as using proper kneading techniques. Presence of rice starch or hydrophilic polymers in the CNF and polyolefin kneading system has a big role in improving the dispersion of the CNF in the composite. It

Air permeability 1) (μm/(Pa・s)

Remarks

large (high heat stability)2)

Gurley value (s/100cc)

> Mariko Yoshioka\* and Yoshiyuki Nishio *Div of Forest & Biomaterials Sci., Graduate School of Agriculture, Kyoto University*