DEGRADABLE POLYMERS - THE ROLE OF THE DEGRADATION ENVIRONMENT

The degradability of several degradable polymers was examined using th ree types of degradation environments. These include exposure in a lab oratory-scale composting test system containing material representativ e of the organic fraction of municipal solid waste (MSW), exposure in a thermal hydrolytic environment consisting of water at 60 degrees C, and exposure in a thermal-oxidative, dry oven environment of 60 degree s C. The results of the investigation clearly indicate that, in additi on to chemical and biological activity which can lead to polymer degra dation, physical restructuring and reorganization of the macromolecula r structure may also occur at temperatures typically found in a compos t environment, resulting in changes in the mechanical properties of th e polymer films. In the case of the polyethylene-modified polymers eva luated in this study, all behaved similarly, but differently from the other polymer types. The polyethylene-based films appeared to be susce ptible to oxidative degradation and should degrade in a composting env ironment providing that there is sufficient air in contact with the fi lm for a sufficient period of time. However, when exposed in a laborat ory composter, it appears that although ideal temperature-time curves may be obtained, the test time period was insufficient in comparison t o the induction period required to achieve the desired thermal oxidati ve degradation.