BIODEGRADATION OF STARCH-POLY(BETA-HYDROXYBUTYRATE-CO-VALERATE) COMPOSITES IN MUNICIPAL ACTIVATED-SLUDGE

Injection-molded composites were prepared by blending PHBV5 with nativ e cornstarch (30% and 50%) and with cornstarch precoated with PEO as a binding agent. These composites were evaluated for their biodegradabi lity in municipal activated sludge by measuring changes in their physi cal and chemical properties over a period of 35 days. All composites l ost weight, ranging from 45 to 78% within 35 days. Interestingly, the extent and rate of weight loss were quite similar in PHBV composites w ith no starch, with 30% starch, and with 50% starch. Weight loss was s lowest in PHBV blends prepared with PEG-coated starch. For all samples , the weight loss was accompanied by a rapid deterioration in tensile strength and percentage elongation. The deterioration of these mechani cal properties exhibited a relative rate of PHBV > starch-PHBV > PEG-c oated starch-PHBV. Changes in starch/PHBV composition after biodegrada tion were quantified by FTIR spectroscopy. Increasing the starch conte nt resulted in more extensive starch degradation, while the PHBV conte nt in the blends became less susceptible to hydrolytic enzymes.