Resistance to Thermal Oxidation of Ethylene Propylene Rubber and Polyhydroxybutyrate Blends

Abstract

The structure, properties, and kinetics of thermal oxidation of blends based on polyhydroxybutyrate (PHB) and ethylene propylene rubber (EPR) were studied. The physicomechanical properties were studied using a ZE-40 tensile testing machine (Germany), and the crystallisation temperature Tcr and melting temperature Tm of PHB in the blends were determined on a DSM-2M differential scanning calorimeter at a scanning rate of 16°C/min. The morphology of films was determined by scanning electron microscopy on a Hitachi S-570 microscope (Japan). The kinetics of thermal oxidation of the blends was assessed according to the amount of absorbed oxygen. With increase in the PHB content in the blend there is a reduction in the elongation at break and an increase in the tensile strength and modulus. Change in the PHB content and in the oxidation time leads to negligible changes in Tcr and Tm. It was established that the greatest reactivity of blends in relation to oxygen is observed in the range of PHB concentrations of 20–40%, where the greatest phase interface area is formed. It was shown that, by changing the ratios of EPR and PHB, it is possible to control the kinetics of thermal oxidation of the blends. It was shown that, in the range of concentrations of 50–70% PHB, phase inversion occurs in the blends.