Degradation kinetics and molecular structure development of hydroxyethyl cellulose under the solid state mechanochemical treatment
The mechanochemical degradation behavior of hydroxyethyl cellulose (HEC) during vibratory ball milling and its induced morphological and structure development of HEC were studied through intrinsic viscosity measurement and scanning electron microscope (SEM), particle size analysis, wide-angle X-ray diffractometry (WAXD) and thermal gravimetry analysis (TG). A degradation kinetic model was proposed to evaluate the effects of ball-milling time on degradation rate of HEC with different initial molecular weights. The fragmentation mechanism is proposed based on the results of FTIR and 13C NMR measurements. The experimental results indicated that the molecular weight decreased sharply with the increase of ball-milling time, charge ratio of steel ball/HEC and the rotational speed. Meanwhile, the fibriform morphology of original HEC was damaged observably and the crystallinity of HEC decreased sharply during the milling, which induced the decrease of the thermal stability.