Thermal and in vitro degradation properties of the NH2-containing PHBV films

Solution-cast poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films were photographed with polyacrylamide that was further partially transformed into amine groups through Hofmann degradation. The resulting NH2-containing PHBV films were incubated in phosphate-buffered saline for up to 360 days to study the abiotic degradability of the films with different polyacrylamide grafting percentage and the effect of the grafting percentage or hydrolysis on the thermal degradation of PHBV. The 360-day static degradation results showed that the maximum weight loss of PHBV reached to 2.50% at 300 days incubation. The value of the NH2-containing PHBV films was much greater than that of PHBV and increased with the polyacrylamide grafting percentage. All thermal degradation temperatures of the NH2-containing PHBV films decreased with the polyacrylamide grafting percentage before or after in vitro degradation. At 360-day incubation, the temperature at the maximum thermal-degradation rate of PHBV films decreased and those of the NH2-containing PHBV films increased compared with the samples without in vitro degradation. Thermal degradation model of PHBV and the NH2-containing PHBV films followed Avrami-Erofeev with index of 0.4 and Mampel Power with index of 2 before in vitro degradation, respectively. However, only Mampel Power with index of 2 was found to be the most frequently used mechanism to represent the thermal decomposition of PHBV in all films after in vitro degradation. (C) 2014 Published by Elsevier Ltd.