Degradation of starch-based high density polyethylene blends containing a prooxidant additive

Abstract

Degradation of starch-based high density polyethylene (HDPE) blends containing natural rubber and zinc stearate as a prooxidant additive was studied. The enzymatic degradation of the starch component was investigated using enzyme ∝-amylase and the thermal oxidative degradation of the HDPE component was carried out by heating the polymer blends in an air-forced oven at 80°c and 100°c. The progress of polymer degradation was monitored by measuring the weight loss and characterized using Extrusion Plastimetry, Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and a Universal Testing Machine. After being subjected to heat treatment, pure HDPE and starch-based HDPE were not found to be degraded, while for HDPE containing the prooxidant additive, the polymer was found to be degraded. For enzymatic รณdies, an increase in the starch content of the polymer blends led to an increase in starch hydrolysis. The degradation rate of polymer blends was found to be accelerated by the combination of thermal oxidative degradation and enzymatic degradation rather than by either mechanism operating alone.