BLOCK-GRAFT COPOLYMERS AS COMPATIBILIZERS IN POLYMER BLENDS

Block copolymers can be good compatibilizers in polymer blends, if tai lored carefully. However, they are produced by anionic polymerization which is not a versatile technique and, moreover, is expensive. Suitab le alternatives are block-graft copolymers, which can be prepared by r adical grafting from readily available block copolymers, in particular from SbB (S, styrene; B, butadiene). The efficiency of two block-graf t copolymers, SbBgCHMA and SbBgMMA (CHMA, cyclohexylmethacrylate; MMA, methyl methacrylate), as compatibilizers in PS/PVC blends of polystyr ene (PS) and poly(vinyl chloride) (PVC) was investigated by electron m icroscopy. Both copolymers refined the coarse morphologies of the PS/P VC blends excellently, covering the interfaces between the phase domai ns of PS and PVC with monolayers. This is in accord with the commonly assumed model of the compatibilizer effect of block copolymers. Howeve r, the phase structures were, in fact, even finer than predicted by th e model: perfectly compatibilized phase domains were torn apart during mixing in the kneader, whereby the morphology was further refined. Co pyright (C) 1996 Elsevier Science Ltd.