Toughening of PBT by ABS, SBS and HIPS systems and the effects of reactive functionalised copolymers

Poly(butylene terephthalate) (PBT) has been toughened by the addition of different impact modifiers such as acrylonitrile-butadiene-styrene (ABS), styrene-butadiene-styrene triblock copolymer (SBS), high impact polystyrene (HIPS) and HIPS/SBS systems with and without reactive compatibilising copolymer. PBT/ABS blends have been modified by methyl methacrylate-co-glycidil methacrylate copolymer (MMA-GMA) and the systems PBT/HIPS and PBT/SBS where modified by an in situ compatibiliser of styrene-co-glycidyl methacrylate copolymer (S-GMA). Addition of ABS A, ABS B, SBS and HIPS/SBS systems at high content of SBS, was very effective in increase the ability of PBT in absorb impact energy. Incorporation of HIPS to PBT at any level did not improve impact strength of the PBT matrix. By adding the acrylic copolymer to the PBT/ABS blends, the high impact strength behaviour of the blends observed at room temperature, has been extended to temperatures well below the room temperature. The effects of addition of reactive copolymer to the morphology of PBT/ABS blends have been studied. The results show the strong influence of the acrylic copolymer in controlling the phase morphology of the system studied. Addition of the styrene-co-glycidil methacrylate copolymer to the 50/25/25 PBT/HIPS/SBS system did not promote a significant decrease in the ductile-brittle transition behaviour for this blend. In fact, incorporation of the high glycidil methacrylate content styrenic compatibiliser has turned the system into brittle over the temperature range studied, i.e., the ductile-brittle transition has been suppressed.