Michael N. Mang

Biodegradation of an Epoxy-Based Thermoplastic Polyester, Poly(Hydroxy Ester Ether) in a Laboratory-Scale Compost System

An epoxy-based thermoplastic polyester, poly(hydroxy ester ether), was incubated under aerobic conditions in a laboratory-scale compost system for 168 days to evaluate its potential for biodegradation. Radiolabeled test polymer [uniformly 14C ring-labeled, poly(hydroxy ester ether)] was incorporated into a mature compost and a sludge-amended compost at a loading of ∼3 mg test polymer/g compost. 14C-Cellulose was used as the positive control and a biologically inhibited control reactor was used to assess abiotic degradation of the test polymer. Degradation of the test polymer was assessed by measuring the amount of 14C-CO2 from each of the test reactors. In addition, at selected time intervals subsamples of the compost were collected and serially extracted with water, methanol, and dimethylformamide to monitor degradation of the 14C-test polymer and provide a partial characterization of the degradation intermediates. Extensive degradation of 14C-poly(hydroxy ester ether) was observed in the test reactors with degradation half-life of the parent polymer (t1/2) of approximately 32 days. By the end of the study, only 2% of the total 14C activity in the test reactors was attributed to intact polymer, with most of the measurable 14C activity converted to either 14C-CO2 (26% of total 14C activity) or nonextractable products (accounting for ∼60% of the total activity). In contrast to the test reactors, only 3% of the 14C-poly(hydroxy ester ether) added to the biologically inhibited control reactor was mineralized to 14C-CO2. The results obtained from the microbially active and biologically inhibited compost systems indicate that the poly(hydroxy ester ether) polymer was degraded, at least in part, by a biologically mediated process.