PVC modified with epoxidized elastomers
Polimery 1997, No 7-8, 482
Thermal dehydrochlorination (170—180°C, oxygen-free atmosphere) and accelerated weathering (up to 31 days) of PVC—epoxidized diene elastomer (10%) blends was studied in relation to the effect of natural rubber ENR25 and linear EB/S or radial E(B/S)n butadiene/styrene triblock copolymers used as10% additions. The elastomers had nearly identical epoxide mer contents (0.25—0.27 mol/100 g). Aging resistance and impact strength of the blend of the epoxidized elastomer carrying reactive groups capable of chemically reacting with PVC's degradation products were found to be related to the structure ofthe macromolecules of the elastomer. The resistance to thermal dehydrochlorination as deduced from the time of induction, t0, and from the maximum rate (Vmax) of evolution of hydrogen chloride from the PVC—epoxidized elastomer blend, was found to decrease in the following order: PVC—ENR25 > PVC—E(B/S)n > PVC—EB/S. In the blends submitted to accelerated-aging conditions crosslinking was found to occur. In 31 days of accelerated aging the blends PVC—ENR25 and PVC—E(B/S)n exhibited similar degrees of retention of the elongation at break, whereas with the PVC—EB/S the degree was considerably lower. Impact strength of the PVC—ENR25 and PVC—EB/S was similar and 6—7 times that of PVC; for the PVC—E(B/S)n, the impact strength was much lower, yet still 3 times that of PVC. The present results indicate that epoxidized elastomers can act both as stabilizers and impact strength modifiers.