Biodegradation Characteristics of Ultrahigh Molecular Weight Polyethylene and Starch Composites Films

publisher[Synopsis] The biodegradative behaviors of composite films of ultrahigh molecular weight polyethylene (6×10＾6) and corn starch particles were investigated. The films were prepared by gelation-crystallization from dilute solutions of polyethylene, in which corn starch particles were dispersed. The polyethylene —corn starch compositions chosen were 3/1 , 1/1, 1/3 and 1/5. The elongation was done up to 80 times in a hot oven at 135°C under nitrogen. Using the undrawn and drawn samples, biodegradation of PE was examined by burying the blend materials for 16 months in three kinds of soils, namely, paddy soil, farmyard manure, and red clay. The weight decrease after the degradation was found to be dependent on corn starch content, draw ratio of original films, type of soils, and burying period. The weight loss was the highest for the sample buried in paddy soil and lowest for that in red clay. Nevertheless, the changes in the tensile strength and Young's modulus after degradation were most prominent in the sample buried in red clay. This result is of interest since the weight decrease in this sample was lowest. Drastic morphological changes were observed by scanning electron microscopy for the samples buried in red clay. Significant chain scission of ultrahigh molecular weight polyethylene was confirmed. The sample buried in red clay showed the largest decrease in storage modulus. The tendency was consistent with the results obtained by the measurement of differential scanningcalorimetry (DSC). No degradation, however, was observed for the ultradrawn ultrahigh molecular weight polyethylene sample (1/0) buried in red clay. Thus it turned out that the biodegradation of PE in the composite materials buried in red clay is induced by the dispersed corn starch particles