when upgrading a material from a low value to a higher value , two main issues need to be considered : the type of potential end - product(s ) and the required properties .
this study focuses on the extrusion of protein - based plastics for potential use in packaging for two reasons .
the present variety of packages is extensive , but the request for renewable and biodegradable low - cost packaging material has increased rapidly in the last decade . this trend seems to be continuing , as most brand owners and legislators are searching for options to create plastics from petroleum .
the required material properties for packaging are , in many cases , more demanding than for other plastic products . however
the exact criteria differ depending on the type of package , filling / sealing systems , transport , storage , content , appearance , product design , etc .
all these parameters should be considered by a packaging developer , but all can not be of the highest priority at once when initiating the development of a new and unexplored material . the properties in focus for this study were the mechanical and barrier performances .
extrusion is the processing method of choice for two reasons : extrusion is a common and efficient method for making packaging plastics , and it generally does not involve a solvent , as in solution casting . thus , no drying step is needed at the end of the process .
it has shown potential as a packaging plastic in a number of studies . despite this , some challenges remain .
crambe abyssinica is an interesting oilseed plant in that it is not a food resource and can be grown in many different agronomic conditions . as with wheat gluten ,
it is obtained as a defatted crambe meal , with protein as the largest component .
it also contains a sizeable amount of nitrogen - free extracts , such as carbohydrates and fiber .
the meal has relatively poor cohesive properties and needs to be blended with a material of higher cohesion . in this study ,
wheat gluten is used as a supportive additive to the crambe meal . to improve the toughness / extensibility of the protein material , a plasticizer is commonly used as an additive as well . in this study ,
glycerol is used , which is a side product of the plant oil industry ( e.g. , rape seed methyl ester fuels ) and is readily available at a low cost .
urea , also renewable , is used as a denaturant in order to give the extrudate the proper cohesion .
renewable materials , especially those that are used directly from nature , without purification , modification , or chemical synthesis , are , in most cases , not suitable for high - temperature treatment .
the challenge is to find suitable processing parameters and compositions that result in an extrudate with properties that allow it to compete with products from petroleum .
this study focuses on the characterization of the mechanical and barrier properties of a new bio - based material produced from crambe meal processed with different additives and at different conditions .
the full details of the mechanical and oxygen barrier features are found in rasel et al ..
note : crambe seeds ( cultivar galactica ) were supplied by the plant research international , wageningen , netherlands .
both the crambe meal and the wheat gluten were stored at -18 c until further use . 

sieving crambe 
 sieve the crambe meal with a round , fine - mesh stainless steel kitchen sieve ( pore size : ~1.5 mm , 14 mesh ) , to remove large fiber fractions and uncrushed seeds .
sieve the crambe meal with a round , fine - mesh stainless steel kitchen sieve ( pore size : ~1.5 mm , 14 mesh ) , to remove large fiber fractions and uncrushed seeds .
milling crambe 
 to reduce the particle size and make the material more homogeneous , mill the sieved crambe meal in a rotary ball mill.mill 250 g of crambe meal each time in a 7 l jar with 21 - 25 mm diameter ceramic balls using a 53 rpm jar revolution rate and a milling time of 24 hr . 
 
to reduce the particle size and make the material more homogeneous , mill the sieved crambe meal in a rotary ball mill . mill 250 g of crambe meal each time in a 7 l jar with 21 - 25 mm diameter ceramic balls using a 53 rpm jar revolution rate and a milling time of 24 hr . 

conditioning 
 before further processing , condition all the ball - milled crambe meal and wheat gluten powder in open jars for a minimum of 48 hr at 23 c and a relative humidity of 50% in a climate - controlled room . 
  before further processing ,
condition all the ball - milled crambe meal and wheat gluten powder in open jars for a minimum of 48 hr at 23 c and a relative humidity of 50% in a climate - controlled room . 
 mixing the components 

grind the urea powder ( stored in a closed beaker at ambient conditions ) to fine particles with a mortar and pestle.blend urea and glycerol ( 25.5 g of glycerol and 15 g of urea per 100 g of the final mixture ) . heat the glycerol to 65 c in a glass flask in an oil bath and
add the urea powder slowly.stir the mixture with a magnetic stirrer at 65 c until the urea powder is completely dissolved . 

 
grind the urea powder ( stored in a closed beaker at ambient conditions ) to fine particles with a mortar and pestle .
blend urea and glycerol ( 25.5 g of glycerol and 15 g of urea per 100 g of the final mixture ) .
heat the glycerol to 65 c in a glass flask in an oil bath and add the urea powder slowly.stir the mixture with a magnetic stirrer at 65 c until the urea powder is completely dissolved . 
 
heat the glycerol to 65 c in a glass flask in an oil bath and add the urea powder slowly . stir the mixture with a magnetic stirrer at 65 c until the urea powder is completely dissolved . 
 mixing the crambe and wheat gluten 

blend the crambe meal powder and wheat gluten powder in a kitchen mixing machine for 5 min .
for example , for a 60/40 ( w / w ) crambe / wheat gluten ratio , use 35.7 g of crambe meal and 23.8 g of wheat gluten per 100 g of the final mixture . 
  blend the crambe meal powder and wheat gluten powder in a kitchen mixing machine for 5 min .
for example , for a 60/40 ( w / w ) crambe / wheat gluten ratio , use 35.7 g of crambe meal and 23.8 g of wheat gluten per 100 g of the final mixture . 

mixing glycerol / urea with crambe / wheat gluten 
 slowly add the glycerol / urea mixture to the crambe / wheat gluten blend in the kitchen mixing machine while stirring the mixture .
prepare 500 g of the mixture each time.for the material with 60/40 ( w / w ) crambe and wheat gluten , use the following relative contents of the respective constituents : 35.7 g of crambe meal , 23.8 g of wheat gluten , 25.5 g of glycerol , and 15 g of urea ( per 100 g ) . for the other two material combinations ( i.e. , 70/30 and 80/20 ) , change only the crambe and wheat gluten contents .
keep the glycerol and urea contents the same as in the 60/40 combination . 
  slowly
add the glycerol / urea mixture to the crambe / wheat gluten blend in the kitchen mixing machine while stirring the mixture .
prepare 500 g of the mixture each time . for the material with 60/40 ( w / w ) crambe and wheat gluten , use the following relative contents of the respective constituents : 35.7 g of crambe meal , 23.8 g of wheat gluten , 25.5 g of glycerol , and 15 g of urea ( per 100 g ) .
for the other two material combinations ( i.e. , 70/30 and 80/20 ) , change only the crambe and wheat gluten contents . keep the glycerol and urea contents the same as in the 60/40 combination . 

low - temperature profile 
 perform the film extrusion in a twin - screw extruder .
set zones 1 - 10 ( each 80 mm - long ) along the extruder barrel at a low temperature profile ( subsequently called " low - t profile " ) , as follows : 75 - 75 - 75 - 80 - 80 - 80 - 80 - 85 - 85 - 85 c .
this prevents the wheat gluten from crosslinking in the barrel.use a flat sheet die ( 45 mm x 0.7 mm ) to extrude the films.choose a screw speed between 30 rpm and 200 rpm and record the die pressure.feed the dough manually through the hopper with the help of a wooden pusher to support the material flow towards the screws.at the die , pick up the extrudate with a conveyor belt operating at a speed of 2.0 m / min .
place air ventilation cooling ( fans ) along the belt.run different die temperatures ( 105 c-(105 c ) , 110 c-(110 c ) , 125 c-(115 c ) , 130 c-(120 c ) , and 140 c-(125 c ) ) to select the conditions that give the smoothest extrudate with a minimum amount of voids .
note : the values in the brackets correspond to the temperature in zone 11 , next to the die .
it is adjusted to reach the target temperature in the die.after extrusion , store the extrudates in sealed polyethylene bags until further processing or analysis in order to prevent ageing and atmospheric water absorption . 
 
set zones 1 - 10 ( each 80 mm - long ) along the extruder barrel at a low temperature profile ( subsequently called " low - t profile " ) , as follows : 75 - 75 - 75 - 80 - 80 - 80 - 80 - 85 - 85 - 85 c .
use a flat sheet die ( 45 mm x 0.7 mm ) to extrude the films . choose a screw speed between 30 rpm and 200 rpm and record the die pressure . feed the dough manually through the hopper with the help of a wooden pusher to support the material flow towards the screws . at the die , pick up the extrudate with a conveyor belt operating at a speed of 2.0 m / min . place air ventilation cooling ( fans ) along the belt .
run different die temperatures ( 105 c-(105 c ) , 110 c-(110 c ) , 125 c-(115 c ) , 130 c-(120 c ) , and 140 c-(125 c ) ) to select the conditions that give the smoothest extrudate with a minimum amount of voids .
note : the values in the brackets correspond to the temperature in zone 11 , next to the die .
after extrusion , store the extrudates in sealed polyethylene bags until further processing or analysis in order to prevent ageing and atmospheric water absorption . 
 film extrusion using the high - temperature profile 
 extrude films as described in section 2.1 , but use a high - temperature profile ( subsequently called " high - t profile " )
, as follows : 85 - 85 - 85 - 100 - 100 - 100 - 110 - 110 - 120 - 120 - 120 c for zones 1 to 11 of the extruder.use die temperatures of 125 c and 130 c . 
 
extrude films as described in section 2.1 , but use a high - temperature profile ( subsequently called " high - t profile " ) , as follows : 85 - 85 - 85 - 100 - 100 - 100 - 110 - 110 - 120 - 120 - 120 c for zones 1 to 11 of the extruder .
film extrusion after pelletization 
 in order to get pellets , extrude the material as continuous strands in the extruder using a two - strand die .
use the low - t profile for the extruder barrel , as described above , and a 60-rpm screw rotational speed.use different die-(zone 11 ) temperatures ( 130 c-(125c ) , 125 c-(115 c ) , 105 c-(100 c ) , and 85 c-(85 c ) ) to obtain the strands with the smoothest surfaces . 

pelletization after passing the conveyor belt ( the belt situated after the extruder that helps to feed material out of the extruder ) , feed the strands into a pelletizer operated with a cutting speed of 7 m / min . 

film extrusion from the pellets feed the pellets manually into the extruder and extrude films with the low - t profile inside the barrel and with a 125 c-(115 c ) flat - sheet die temperature . use a screw rotational speed of 30 rpm . 

  in order to get pellets ,
extrude the material as continuous strands in the extruder using a two - strand die .
use the low - t profile for the extruder barrel , as described above , and a 60-rpm screw rotational speed.use different die-(zone 11 ) temperatures ( 130 c-(125c ) , 125 c-(115 c ) , 105 c-(100 c ) , and 85 c-(85 c ) ) to obtain the strands with the smoothest surfaces . 
  use the low - t profile for the extruder barrel , as described above , and a 60-rpm screw rotational speed . use different die-(zone 11 ) temperatures ( 130 c-(125c ) , 125 c-(115 c ) , 105 c-(100 c ) , and 85 c-(85 c ) ) to obtain the strands with the smoothest surfaces .
pelletization after passing the conveyor belt ( the belt situated after the extruder that helps to feed material out of the extruder ) , feed the strands into a pelletizer operated with a cutting speed of 7 m / min . 
  after passing the conveyor belt ( the belt situated after the extruder that helps to feed material out of the extruder ) , feed the strands into a pelletizer operated with a cutting speed of 7 m / min .
film extrusion from the pellets feed the pellets manually into the extruder and extrude films with the low - t profile inside the barrel and with a 125 c-(115 c ) flat - sheet die temperature . use a screw rotational speed of 30 rpm . 
 
feed the pellets manually into the extruder and extrude films with the low - t profile inside the barrel and with a 125 c-(115 c ) flat - sheet die temperature . use a screw rotational speed of 30 rpm . 

film extrusion using volumetric feeding 
 in order to simulate automatic feeding ( commonly used in industry ) , use the pellets previously extruded at 85 c ( steps 2.3.1 - 2.3.2.1).connect the feeder to the extruder and choose the volumetric feeder mode of the hopper.use a feeding volume of 35 kg / h and hopper and extruder screw speeds of 16 and 120 rpm , respectively.extrude with the low temperature profile of the barrel and use a die-(zone 11 ) temperature of 125 c-(115 c ) . 
  in order to simulate automatic feeding ( commonly used in industry ) , use the pellets previously extruded at 85 c ( steps 2.3.1 - 2.3.2.1 ) .
connect the feeder to the extruder and choose the volumetric feeder mode of the hopper . use a feeding volume of 35 kg / h and hopper and extruder screw speeds of 16 and 120 rpm , respectively .
extrude with the low temperature profile of the barrel and use a die-(zone 11 ) temperature of 125 c-(115 c ) . 
 pressing with the frame 
 for the first setup , cut two extrudates into pieces of 4.4 cm x 7.0 cm and 2.6 cm x 7.0 cm .
note : this is needed because the frame is broader than the extrudates.place them next to each other in an aluminum rectangular frame ( 70 x 70 x 0.5 mm).sandwich the frame between two aluminum plates using poly(ethylene terephthalate ) ( pet ) films on both sides to prevent adhesion , and then place them into the press.set the pressure gauge on the press to 200 or 400 bar.for each molding pressure , press the films with a plate temperature of 110 , 120 , and 130 c for 10 and 20 min.as a reference to the pre - extruded samples , press films from unextruded material . center 7.2 g of fresh material ( from section 1.6 ) in the aluminum frame.press with the same parameter settings as for the pre - extruded films above ( steps 3.1.4- 3.1.5 ) . 
 
for the first setup , cut two extrudates into pieces of 4.4 cm x 7.0 cm and 2.6 cm x 7.0 cm .
place them next to each other in an aluminum rectangular frame ( 70 x 70 x 0.5 mm ) .
sandwich the frame between two aluminum plates using poly(ethylene terephthalate ) ( pet ) films on both sides to prevent adhesion , and then place them into the press .
for each molding pressure , press the films with a plate temperature of 110 , 120 , and 130 c for 10 and 20 min . as a reference to the pre - extruded samples , press films from unextruded material .
center 7.2 g of fresh material ( from section 1.6 ) in the aluminum frame .
press with the same parameter settings as for the pre - extruded films above ( steps 3.1.4- 3.1.5 ) . 
 pressing without a frame 
 cut out and sandwich rectangular samples ( 4.4 cm x 4.4 cm ) between two aluminum plates using pet films on both sides to prevent adhesion.place them into the press .
set the pressure gauge to 50 bar , 75 bar , or 100 bar.for each molding pressure , press films for 5 or 10 min using 110 c , 120 c and 130 c plate temperatures . 
 
cut out and sandwich rectangular samples ( 4.4 cm x 4.4 cm ) between two aluminum plates using pet films on both sides to prevent adhesion .
for each molding pressure , press films for 5 or 10 min using 110 c , 120 c and 130 c plate temperatures .

 sieving crambe 
 sieve the crambe meal with a round , fine - mesh stainless steel kitchen sieve ( pore size : ~1.5 mm , 14 mesh ) , to remove large fiber fractions and uncrushed seeds . store the sieved meal at -18 c to prevent material ageing . 
 
sieve the crambe meal with a round , fine - mesh stainless steel kitchen sieve ( pore size : ~1.5 mm , 14 mesh ) , to remove large fiber fractions and uncrushed seeds .
milling crambe 
 to reduce the particle size and make the material more homogeneous , mill the sieved crambe meal in a rotary ball mill.mill 250 g of crambe meal each time in a 7 l jar with 21 - 25 mm diameter ceramic balls using a 53 rpm jar revolution rate and a milling time of 24 hr . 
  to reduce the particle size and make the material more homogeneous , mill the sieved crambe meal in a rotary ball mill
. mill 250 g of crambe meal each time in a 7 l jar with 21 - 25 mm diameter ceramic balls using a 53 rpm jar revolution rate and a milling time of 24 hr . 

conditioning 
 before further processing , condition all the ball - milled crambe meal and wheat gluten powder in open jars for a minimum of 48 hr at 23 c and a relative humidity of 50% in a climate - controlled room . 
  before further processing ,
condition all the ball - milled crambe meal and wheat gluten powder in open jars for a minimum of 48 hr at 23 c and a relative humidity of 50% in a climate - controlled room . 
 mixing the components 

grind the urea powder ( stored in a closed beaker at ambient conditions ) to fine particles with a mortar and pestle.blend urea and glycerol ( 25.5 g of glycerol and 15 g of urea per 100 g of the final mixture ) . heat the glycerol to 65 c in a glass flask in an oil bath and
add the urea powder slowly.stir the mixture with a magnetic stirrer at 65 c until the urea powder is completely dissolved . 

 
grind the urea powder ( stored in a closed beaker at ambient conditions ) to fine particles with a mortar and pestle .
blend urea and glycerol ( 25.5 g of glycerol and 15 g of urea per 100 g of the final mixture ) .
heat the glycerol to 65 c in a glass flask in an oil bath and add the urea powder slowly.stir the mixture with a magnetic stirrer at 65 c until the urea powder is completely dissolved . 
 
heat the glycerol to 65 c in a glass flask in an oil bath and add the urea powder slowly .
stir the mixture with a magnetic stirrer at 65 c until the urea powder is completely dissolved . 
 mixing the crambe and wheat gluten 

blend the crambe meal powder and wheat gluten powder in a kitchen mixing machine for 5 min .
for example , for a 60/40 ( w / w ) crambe / wheat gluten ratio , use 35.7 g of crambe meal and 23.8 g of wheat gluten per 100 g of the final mixture . 
  blend the crambe meal powder and wheat gluten powder in a kitchen mixing machine for 5 min .
for example , for a 60/40 ( w / w ) crambe / wheat gluten ratio , use 35.7 g of crambe meal and 23.8 g of wheat gluten per 100 g of the final mixture . 

mixing glycerol / urea with crambe / wheat gluten 
 slowly add the glycerol / urea mixture to the crambe / wheat gluten blend in the kitchen mixing machine while stirring the mixture .
prepare 500 g of the mixture each time.for the material with 60/40 ( w / w ) crambe and wheat gluten , use the following relative contents of the respective constituents : 35.7 g of crambe meal , 23.8 g of wheat gluten , 25.5 g of glycerol , and 15 g of urea ( per 100 g ) . for the other two material combinations ( i.e. , 70/30 and 80/20 ) , change only the crambe and wheat gluten contents .
slowly add the glycerol / urea mixture to the crambe / wheat gluten blend in the kitchen mixing machine while stirring the mixture .
for the material with 60/40 ( w / w ) crambe and wheat gluten , use the following relative contents of the respective constituents : 35.7 g of crambe meal , 23.8 g of wheat gluten , 25.5 g of glycerol , and 15 g of urea ( per 100 g ) . for the other two material combinations ( i.e. , 70/30 and 80/20 ) , change only the crambe and wheat gluten contents . keep the glycerol and urea contents the same as in the 60/40 combination .

 low - temperature profile 
 perform the film extrusion in a twin - screw extruder . set zones 1 - 10 ( each 80 mm - long ) along the extruder barrel at a low temperature profile ( subsequently called " low - t profile " ) , as follows : 75 - 75 - 75 - 80 - 80 - 80 - 80 - 85 - 85 - 85 c .
this prevents the wheat gluten from crosslinking in the barrel.use a flat sheet die ( 45 mm x 0.7 mm ) to extrude the films.choose a screw speed between 30 rpm and 200 rpm and record the die pressure.feed the dough manually through the hopper with the help of a wooden pusher to support the material flow towards the screws.at the die , pick up the extrudate with a conveyor belt operating at a speed of 2.0 m / min .
place air ventilation cooling ( fans ) along the belt.run different die temperatures ( 105 c-(105 c ) , 110 c-(110 c ) , 125 c-(115 c ) , 130 c-(120 c ) , and 140 c-(125 c ) ) to select the conditions that give the smoothest extrudate with a minimum amount of voids .
note : the values in the brackets correspond to the temperature in zone 11 , next to the die .
it is adjusted to reach the target temperature in the die.after extrusion , store the extrudates in sealed polyethylene bags until further processing or analysis in order to prevent ageing and atmospheric water absorption . 
 
perform the film extrusion in a twin - screw extruder . set zones 1 - 10 ( each 80 mm - long ) along the extruder barrel at a low temperature profile ( subsequently called " low - t profile " ) , as follows : 75 - 75 - 75 - 80 - 80 - 80 - 80 - 85 - 85 - 85 c .
use a flat sheet die ( 45 mm x 0.7 mm ) to extrude the films . choose a screw speed between 30 rpm and 200 rpm and record the die pressure . feed the dough manually through the hopper with the help of a wooden pusher to support the material flow towards the screws . at the die , pick up the extrudate with a conveyor belt operating at a speed of 2.0 m / min . place air ventilation cooling ( fans ) along the belt .
run different die temperatures ( 105 c-(105 c ) , 110 c-(110 c ) , 125 c-(115 c ) , 130 c-(120 c ) , and 140 c-(125 c ) ) to select the conditions that give the smoothest extrudate with a minimum amount of voids .
note : the values in the brackets correspond to the temperature in zone 11 , next to the die .
after extrusion , store the extrudates in sealed polyethylene bags until further processing or analysis in order to prevent ageing and atmospheric water absorption . 

film extrusion using the high - temperature profile 
 extrude films as described in section 2.1 , but use a high - temperature profile ( subsequently called " high - t profile " ) , as follows : 85 - 85 - 85 - 100 - 100 - 100 - 110 - 110 - 120 - 120 - 120 c for zones 1 to 11 of the extruder.use die temperatures of 125 c and 130 c . 
  extrude films as described in section 2.1 , but use a high - temperature profile ( subsequently called " high - t profile " ) , as follows : 85 - 85 - 85 - 100 - 100 - 100 - 110 - 110 - 120 - 120 - 120 c for zones 1 to 11 of the extruder .
film extrusion after pelletization 
 in order to get pellets , extrude the material as continuous strands in the extruder using a two - strand die .
use the low - t profile for the extruder barrel , as described above , and a 60-rpm screw rotational speed.use different die-(zone 11 ) temperatures ( 130 c-(125c ) , 125 c-(115 c ) , 105 c-(100 c ) , and 85 c-(85 c ) ) to obtain the strands with the smoothest surfaces . 

pelletization after passing the conveyor belt ( the belt situated after the extruder that helps to feed material out of the extruder ) , feed the strands into a pelletizer operated with a cutting speed of 7 m / min . 

film extrusion from the pellets feed the pellets manually into the extruder and extrude films with the low - t profile inside the barrel and with a 125 c-(115 c ) flat - sheet die temperature .
use a screw rotational speed of 30 rpm . 

  in order to get pellets ,
extrude the material as continuous strands in the extruder using a two - strand die .
use the low - t profile for the extruder barrel , as described above , and a 60-rpm screw rotational speed.use different die-(zone 11 ) temperatures ( 130 c-(125c ) , 125 c-(115 c ) , 105 c-(100 c ) , and 85 c-(85 c ) ) to obtain the strands with the smoothest surfaces . 
  use the low - t profile for the extruder barrel , as described above , and a 60-rpm screw rotational speed . use different die-(zone 11 )
temperatures ( 130 c-(125c ) , 125 c-(115 c ) , 105 c-(100 c ) , and 85 c-(85 c ) ) to obtain the strands with the smoothest surfaces .
pelletization after passing the conveyor belt ( the belt situated after the extruder that helps to feed material out of the extruder ) , feed the strands into a pelletizer operated with a cutting speed of 7 m / min . 
  after passing the conveyor belt ( the belt situated after the extruder that helps to feed material out of the extruder ) , feed the strands into a pelletizer operated with a cutting speed of 7 m / min .
film extrusion from the pellets feed the pellets manually into the extruder and extrude films with the low - t profile inside the barrel and with a 125 c-(115 c ) flat - sheet die temperature .
use a screw rotational speed of 30 rpm . 
  feed the pellets manually into the extruder and
extrude films with the low - t profile inside the barrel and with a 125 c-(115 c ) flat - sheet die temperature .
film extrusion using volumetric feeding 
 in order to simulate automatic feeding ( commonly used in industry ) , use the pellets previously extruded at 85 c ( steps 2.3.1 - 2.3.2.1).connect the feeder to the extruder and choose the volumetric feeder mode of the hopper.use a feeding volume of 35 kg / h and hopper and extruder screw speeds of 16 and 120 rpm , respectively.extrude with the low temperature profile of the barrel and use a die-(zone 11 ) temperature of 125 c-(115 c ) . 
  in order to simulate automatic feeding ( commonly used in industry ) , use the pellets previously extruded at 85 c ( steps 2.3.1 - 2.3.2.1 ) . connect the feeder to the extruder and
use a feeding volume of 35 kg / h and hopper and extruder screw speeds of 16 and 120 rpm , respectively .
extrude with the low temperature profile of the barrel and use a die-(zone 11 ) temperature of 125 c-(115 c ) .

 pressing with the frame 
 for the first setup , cut two extrudates into pieces of 4.4 cm x 7.0 cm and 2.6 cm x 7.0 cm . note : this is needed because the frame is broader than the extrudates.place them next to each other in an aluminum rectangular frame ( 70 x 70 x 0.5 mm).sandwich the frame between two aluminum plates using poly(ethylene terephthalate ) ( pet ) films on both sides to prevent adhesion , and then place them into the press.set the pressure gauge on the press to 200 or 400 bar.for each molding pressure , press the films with a plate temperature of 110 , 120 , and 130 c for 10 and 20 min.as a reference to the pre - extruded samples , press films from unextruded material . center 7.2 g of fresh material ( from section 1.6 ) in the aluminum frame.press with the same parameter settings as for the pre - extruded films above ( steps 3.1.4- 3.1.5 ) . 
  for the first setup , cut two extrudates into pieces of 4.4 cm x 7.0 cm and 2.6 cm x 7.0 cm . note
place them next to each other in an aluminum rectangular frame ( 70 x 70 x 0.5 mm ) .
sandwich the frame between two aluminum plates using poly(ethylene terephthalate ) ( pet ) films on both sides to prevent adhesion , and then place them into the press .
for each molding pressure , press the films with a plate temperature of 110 , 120 , and 130 c for 10 and 20 min . as a reference to the pre - extruded samples , press films from unextruded material .
center 7.2 g of fresh material ( from section 1.6 ) in the aluminum frame .
press with the same parameter settings as for the pre - extruded films above ( steps 3.1.4- 3.1.5 ) . 
 pressing without a frame 
 cut out and sandwich rectangular samples ( 4.4 cm x 4.4 cm ) between two aluminum plates using pet films on both sides to prevent adhesion.place them into the press .
set the pressure gauge to 50 bar , 75 bar , or 100 bar.for each molding pressure , press films for 5 or 10 min using 110 c , 120 c and 130 c plate temperatures . 
 
cut out and sandwich rectangular samples ( 4.4 cm x 4.4 cm ) between two aluminum plates using pet films on both sides to prevent adhesion .
for each molding pressure , press films for 5 or 10 min using 110 c , 120 c and 130 c plate temperatures .
the blended materials ( 60 wt% crambe meal and 40 wt% wheat gluten ) resulted in a tough dough after the initial mixing procedure . the material was rested for a few minutes before the first extrusion .
however , the dough had a too high a viscosity to be able to be fed into the extruder hopper in a regular manner .
therefore , it was fed piece - by - piece , directly into the screw .
the screws had a constant speed , and the resulting film extrudate was continuous and had a visually smooth surface .
the die pressure and temperature were found to be the two most important processing parameters to control in order to obtain homogeneous and smooth film extrudates . too low a die temperature , typically below 110 c , did not result in continuous film extrudates , whereas a temperature above 130 c resulted in the formation of bubbles in the material . the most suitable die temperature to obtain homogeneous and smooth films
a two - step process was found to be advantageous , where , in the first step , strands were extruded at a lower temperature ( typically 85 c ) and pelletized .
when the urea content was decreased from 15 to 10 wt% , the cohesion of the dough decreased substantially , resulting in a powder - like material ; no continuous film could be extruded . when the glycerol concentration was decreased ( with a retained 15 wt% urea ) ,
the dough was found to be more brittle , and the urea did not fully dissolve in the glycerol . also , a considerably higher die pressure was required to get homogeneous films .
however , these films were found to be smoother and more homogeneous than those with a higher glycerol content .
when increasing the crambe meal powder concentration and decreasing the wheat gluten concentration , the extruded films appeared darker , but also smoother and more homogeneous . the feeding rate could also be increased .
the drawback was that the films were only partially continuous , and film breakages appeared a few meters apart .
however , when increasing the die temperature to approximately 130 c , continuous films could be prepared , although with some discolorations . compression molding without a frame yielded thin ( thickness : 0.1 - 0.2 mm ) films that were very flexible and translucent ( figure 2 ) . depending on how the extrudates were made and what they contained , the stiffness ranged from 4.9 - 5.6 mpa and the strength from 0.3 - 0.7 mpa , whereas the extensibility ranged from 7 to 16% .
the corresponding values for the extrudates after compression molding were 6.4 - 15.0 mpa , 0.3 - 1.1 mpa , and 8 - 19% .
64 mm - long dumbbell specimens were tensile - tested according to astm d882 - 02 at 23  1 c and 50  1% rh , with a crosshead speed of 10 mm / min .
figure 3 shows the importance of extruding crambe with the addition of wheat gluten . the strength , and especially the extensibility , decreased with decreasing wheat gluten content .
the oxygen permeability ranged from 17 to 39 cm mm/(day m atm ) , depending on the composition and whether a compression molding step ( with a frame ) was used or not .
figure 1 : extruded material . extruded film using a die temperature of 130 c .
it contains 35.7 wt% crambe , 23.8 wt% wheat gluten , 25.5 wt% glycerol , and 15 wt% urea .
extruded material compression - molded , without a frame , into thin , translucent films using a 130 c press temperature at 75 bar for 10 min .
. maximum stress ( filled circles ) and strain at maximum stress ( open circles ) as a function of crambe content in the crambe / wheat gluten mixture .
maximum stress was obtained from the maximum force per initial sample cross - section of the narrow part of the dumbbell specimen ( narrow section : 16 mm long and 4 mm wide ) .
the low - temperature profile was used with an initial die temperature of 125 c and a zone 11 temperature of 115 c .
the screw speed was 30 rpm , and the extrusion was performed without prior pelletization .
the reason the die pressure was of such high importance was probably due to the fact that the material needed a certain pressure to avoid bubble formation . however , the different components could phase separate if the pressure was too high .
when extruding at too low a temperature , the cohesion was poor , possibly due to a low degree of crosslinking , while too high a temperature resulted in the release of gas ( probably moisture together with urea and protein degradation products ) . the two step extrusion ( i.e. , where strands were first extruded , pelletized , and then extruded again ) resulted in a more homogeneous extrudate because of the more extensive blending that the first extrusion step provided . the poor dough cohesion when decreasing the urea concentration from 15 to 10 wt% was probably due to a lower crosslink density . in analogy to this , a lower glycerol concentration , and thus a lower ability to dissolve the urea , resulted in poorer films unless a higher die pressure was applied . increasing the crambe meal concentration , and thus decreasing
the wheat gluten concentration , resulted in a lower degree of aggregation / network formation .
this lowered the viscosity of the material in the extrudate , resulting in the need to increase the die temperature to 130 c to raise the viscosity and generate homogeneous films .
it is difficult , if not impossible , to extrude plasticized crambe into films of sufficient quality for any use .
we show here that this can be overcome by blending crambe with a more readily extrudable protein like wheat gluten . for the best quality ,
it is shown here that extrusion works on a smaller scale , and upscaling is likely to be more demanding .
extrusion , along with injection molding , are the most important commercial methods for producing plastics . in order to replace existing conventional plastics ,
we show here that it is possible to extrude crambe oilseed meal with the help of wheat gluten .
possible applications include packaging and applications for various extruded profiles ( e.g. , rods and cylinders ) .
we consider the most critical step during the preparation of the samples to be the extrusion step .
the final quality of the films depended strongly upon the extrusion parameters and the properties of the material prior to extrusion .
 crambe abyssinica is a plant with potential for use in industrial ( non - food ) plant oil production . 
 the side stream from this oil production is a high - protein crambe meal that has limited value , as it is not fit for food or feed use . 
 however , it contains proteins that could potentially make it a suitable raw material for higher - value products . 
 the purpose of this study was to find methods of making this side stream into extruded films , showing that products with a higher value can be produced . 
 the study mainly considered the development of material compositions and methods of preparing and extruding the material . 
 wheat gluten was added as a supportive protein matrix material , together with glycerol as a plasticizer and urea as a denaturant . 
 the extrudate was evaluated with respect to mechanical ( tensile testing ) and oxygen barrier properties , and the extrudate structure was revealed visually and by scanning electron microscopy . a denser , more homogeneous material had a lower oxygen transmission rate , higher strength , and higher extensibility . 
 the most homogeneous films were made at an extruder die temperature of 125 - 130 c . 
 it is shown here that a film can be extruded with promising mechanical and oxygen barrier properties , the latter especially after a final compression molding step . 
Introduction
Protocol
1. Dough Preparation
2. Film Extrusion
3. Post-extrusion Process (Compression Molding)
Representative Results
Discussion
Disclosures