Effect of Co-60 gamma-radiation on the properties of poly(hydroxybutyrate-co-hydroxyvalerate)

The effects of Co-60 gamma-radiation on the properties of poly(hydroxybutyr ate-co-hydroxyvalerate) (PHBV), including the chemical, mechanical, and the rmal properties, were investigated. Molecular weight of the irradiated PHBV as measured using a Ubbelohde-type capillary viscometer decreased signific antly. Fourier transform infrared-attenuated total reflection (FTIR-ATR) an d H-1 nuclear magnetic resonance (NMR) spectra show that chain scission was the predominant reaction in the PHBV irradiated with 10 and 25 MRad doses; The G(S) value for the chain scission was 0.9, and the number of bond clea vages per molecule was 0.22 MRad(-1). Thermal and tensile properties of con trol and irradiated PHBV were examined using a differential scanning calori meter (DSC) and an Instron tensile testing machine, respectively. Results i ndicate that Co-60 gamma-radiation significantly affected the thermal and t ensile properties of PHBV. The melting temperatures of the irradiated PHBV decreased. Tensile strength and fracture strain of the irradiated PHBV decr eased dramatically, indicating increased brittleness. The fracture surfaces studied using a scanning electron microscope (SEM) showed some voids and a brittle fracture surface. (C) 1999 John Wiley & Sons, Inc.