Toughness enhancement of high-impact polystyrene based on γ-radiation vulcanized natural rubber latex by using block copolymer

Polyisoprene-block-polystyrene-block-polyisoprene (ISI) was synthesized by the iniferter route and its use, as compared to a commercial polystyrene-block-polyisoprene-block-polystyrene (SIS), in the enhancement of the toughness of high-impact polystyrene (HIPS), prepared by the γ-radiation vulcanized natural rubber (RVNR) latex/phase transfer/bulk polymerization technique, was investigated. Addition of 5% SIS was adequate as an interfacial agent, which effectively increased the unnotched Izod impact energy of HIPS, whereas use of 10% of ISI was required. A long polyisoprene block with two polystyrene segments of SIS was favorable for compatibilization of HIPS. Transmission electron micrographs revealed the uniform distribution of the block copolymer at the shell region of the rubber particle. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1307–1316, 2002