Effects of sub T-g annealing on the mechanical properties of polycarbonate/poly(ether ester) copolymer blends

To improve the impact strength of polycarbonate (PC) and reduce hardening o f PC after sub T-g annealing at 140 degrees C a thermoplastic elastomer, po ly(butylene terephthalate-co-tetramethylene glycol) (PBT-PTMG) was melt mix ed with PC. A transesterification inhibitor was added to inhibit reaction b etween PC and PET segments during mixing and annealing. Partial miscibility between PC and PET segments observed for as-molded blends prevents the PBT -PTMG added from fully crystallizing upon cooling, thus acting as an impact modifier of PC. However, the phase separation proceeds as the blends are a nnealed at 140 degrees C, which is below T-g of PC. This causes increase in the crystallinity of PET segments, which acts as physical crosslinks, and thus enhances the toughness of PC physically aged.