Phase morphology development during processing of compatibilized and uncompatibilized PBT/ABS blends

Abstract

The development of the multiphase morphology of uncompatibilized blends of poly(butylene terephthalate) (PBT) and acrylonitrile–butadiene–styrene terpolymer (ABS) and PBT/ABS blends compatibilized with methyl-methacrylate glycidyl-methacrylate (MMA-GMA) reactive copolymers during compounding in a twin-screw extruder and subsequent injection molding was investigated. Uncompatibilized PBT/ABS 60/40 (wt %) and compatibilized PBT/ABS/MMA-GMA with 2 and 5 wt % of MMA-GMA showed refined cocontinuous morphologies at the front end of the extruder, which coarsened towards the extruder outlet. Coarsening in uncompatibilized PBT/ ABS blends is much more pronounced than in the compatibilized PBT/ABS/MMA-GMA equivalents and decreases with increasing amounts of the MMA-GMA. For both systems, significant refinement on the phase morphology was found to occur after the blends pass through the extruder die. This phenomenon was correlated to the capacity of the die in promoting particles break-up due to the extra elongational stresses developed at the matrix entrance. Injection molding induces coarsening of the ABS domains in the case of uncompatibilized PBT/ABS blends, while the reactive blend kept its refined phase morphology. Therefore, the compatibilization process of PBT/ABS/ MMA-GMA blends take place progressively leading to a further refinement of the phase morphology in the latter steps, owing to the slow reaction rate relative to epoxide functions and the carboxyl/hydroxyl groups.