STUDIES ON RUBBER BLEND

(PART XII) SOFTENING PHENOMENON AFTER REMILLING OF STYRENE-BUTADIENE COPOLYMER RUBBER-GENERAL PURPOSE POLYSTYRENE RESIN BLENDS

Abstract

The softening phenomenon after remilling of uncured blends of various styrene-butadiene copolymer rubbers on today′s market (styrene content: 23.5-48wt%, styrene block:0-18%) and general purpose polystyrene resin was mainly studied and the curves of blend ratio dependence of hardness and compression modulus (in logarithm) were examined, paying attention to the dispersion state of polymers.
And it was found that styrene-butadiene copolymer rubber-general purpose polystyrene resin blend forms a microheterogeneous blend system and the hardness and compression modulus change in “S” shaped curves against blend ratio. But random-type styrene-butadiene copolymer rubber and block-type styrene-butadiene copolymer rubber differ from each other in softening effect by remilling (the roll surface temperature: 70-90°C). The effect is more remarkable in case of random-type and the softening effect after remilling was not observed in case of some block-type rubbers. An influence of styrene content is small.
Further considerations on these differences in softening effect among different kinds of styrene-butadiene copolymer rubbers have shown us that the dispersion state of polymers is controlled by a strong mutual interaction between block parts of copolymers and general purpose polystyrene resin, which results in the above phenomenon.