EVALUATION OF BIODEGRADABILITIES OF BIOSYNTHETIC AND CHEMOSYNTHETIC POLYESTERS IN RIVER WATER

Biodegradabilities of 21 samples of biosynthetic and chemosynthetic po lyesters were measured at 25 degrees C under aerobic conditions in a t emperature-controlled reactor containing 200 mi of natural water from the river Arakawa (Saitama, Japan) as an inoculum, by monitoring the t ime-dependent changes in the biochemical oxygen demand (BOD), weight l oss (erosion) of polyester film and dissolved organic carbon concentra tion (DOG) of the test solution. The microbial copolyesters, poly(3-hy droxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-4-hydro xybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxypropionate), were d egraded in the river water at a rapid rate, and the weight-loss- and B OD-biodegradabilities of the majority of biosynthetic polyesters were 100 and 80% +/- 5% for 28 days, respectively. In contrast, the biodegr adabilities of chemosynthetic polyesters were strongly dependent on th e chemical structure and decreased in the following order: poly(ethyle ne succinate) > poly(epsilon-caprolactone) > poly(ethylene adipate) > poly(butylene adipate)> poly(butylene sebacate)> poly(ethylene sebacat e) = poly(butylene succinate)= poly(hexylene succinate) = poly(beta-pr opiolactone).