Effect of reactive compatibilization on the morphology and physical properties of bisphenol-A-polycarbonate/acrylonitrile-butadiene-styrene blends

An amine functional styrene-acrylonitrile (SAN-amine) polymer is proposed as a reactive compatibilizer for bisphenol-A-polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends. This polymer is miscible with the styrene/acrylonitrile (SAN) copolymer matrix of ABS materials, and the pendant secondary amine groups react with PC at the carbonate linkage to form a SAN-g-PC copolymer. The graft copolymer molecules reside at the PC/ABS interface and provide improved morphological stability at elevated temperatures by suppressing phase coalescence. The synthesis of this reactive compatibilizer and its reaction with carbonate moieties is described. Characterization of this reaction was done by NMR and GPC using model secondary amine and carbonate containing compounds. A technique was developed for the quantitative measurement of the kinetics of dispersed phase particle coalescence in these blends; the morphology was examined using TEM. While uncompatibilized PC/SAN blends showed an increase in particle size from approximately 1 {dollar}mu{dollar}m to 2 {dollar}mu{dollar}m (depending on PC viscosity) in less than five minutes at 270{dollar}spcirc{dollar}C; compatibilized blends containing as little as 1% SAN-amine exhibited no change in morphology after 20 minutes.; The effects of dispersed phase concentration, viscosity ratio and interfacial compatibilization using the SAN-amine compatibilizer on the process induced morphology of PC/SAN blends were also examined. Dispersed phase particle size increased significantly with SAN concentration and, although the morphology of uncompatibilized PC/SAN blends mixed in a Brabender mixer, single and twin screw extruders were quite similar, the twin screw extruder produced significantly finer morphologies in blends containing SAN-amine. The average particle size for blends compatibilized with the SAN-amine polymer was approximately half that of uncompatibilized blends and was relatively independent of viscosity ratio and dispersed phase composition.; The fracture of thin (3.18 mm) and thick (6.35 mm) specimens of PC, ABS and PC/ABS blends with both standard and sharp notches was examined by standard Izod and single edge notch three point bend (SEN3PB) instrumented drop tower tests. Load-deflection data were analyzed as a function of ligament length and fracture parameters were calculated using the theoretical framework of the essential work of fracture concept. The effects of blend composition, temperature, rubber concentration and reactive compatibilization on the fracture properties of these materials were examined.