A COMPARATIVE-STUDY OF THE DEGRADABILITY AND RECYCLABILITY OF DIFFERENT CLASSES OF DEGRADABLE POLYETHYLENE

Abiotic degradation of representative samples from available commercial photo(bio)degradable polyethylene films was examined with respect to the rate and extent of degradation, oxidation products, and changes in molecular weight both during outdoor exposure and in laboratory photoaging devices with different accelerating factors. Although the rate of photoxidation was found to depend on the type of degradation system used, all the samples showed rapid rate of carbonyl formation with concomitant reduction in molecular weight and mechanical properties on exposure to UV light. The photofragmented polymers were shown to be much more hydrophilic in nature compared to the unoxidized analogues, and photofragments of all samples were found to contain high levels of low molecular weight( bioassimilable) carboxylic acids and esters. Recycling behavior of virgin polyolefins, both as homopolymers and heterogenous polymer blends, which contained 10% of nonoxidized and photooxidized photo(bio)degradable plastics was examined. It was found that the initial mechanical performance of homogeneous blends was not greatly affected by the presence of nonoxidized degradable materials. However, blends containing degradable films which were initially partially photooxidized had a much more detrimental effect on the recycled blends properties during processing and weathering; the effect was minimal for degradable polymers containing the iron-nickel dithiocarbamate system.