Hot drawing of partially miscible blends of polycarbonate and poly(butylene terephthalate)

Abstract

Samples of PC-PBT blends over the entire composition range were drawn at 1600°C to high extensions, 2.1-5.8, to study the mechanical reinforcement and the molecular structure development upon deformation. Elastic modulus E' increases with extension ratio for all compositions and temperatures. Blends with 25 and 40 wt % of PC show higher E' at low temperature than pure PBT blends do. Crystallinity increases with extension ratio and is relatively smaller with increasing PC content. The influence of the reversible α to β crystal form transformation was also studied. The second moment of the orientation function f for both crystal forms increases to high values > 0.9 at relatively low extensions. f decreases with PC content for α crystals but decreases for β crystals. The α fraction is high fbr PBT and decreases with PC content and extension ratio in the blends. Strain recovery experiments show that the α to β transformation is also elastic in nature at high extension ratios and that the reinforcing effect in high PHT content blends is not due to the α/β ratio.