DEGRADATION OF ENHANCED ENVIRONMENTALLY DEGRADABLE POLYETHYLENE IN BIOLOGICAL AQUEOUS-MEDIA - MECHANISMS DURING THE 1ST STAGES

Degradation of LDPE films containing a biodegradable starch filler and a pro-oxidant formulation was performed in aqueous media inoculated with bacteria or fungi at ambient temperatures for 1 year. The samples were characterized with the aim of elucidating the mechanisms that occur during the first stages and that are responsible for initiating the degradation of the LDPE matrix. Two interactive mechanisms were observed: The basal salt medium (water containing trace elements) triggered autoxidation of the pro-oxidant through decomposition of trace hydroperoxides, which, in synergistic combination with biodegradation of the starch, eventually initiated autoxidation of the LDPE matrix as monitored by chemiluminescence (CL), differential scanning calorimetry (DSC), and confocal scanning laser microscopy (CSLM). The length of the induction period was dependent on the sample thickness and on the activity of the microbiological system. Up to 48% of the starch was consumed during the first year as revealed by polarized-light microscopy. (C) 1994 John Wiley & Sons, Inc.