TOUGHENING PET BY BLENDING WITH A FUNCTIONALIZED SEBS BLOCK-COPOLYMER

Toughened poly(ethylene terephthalate) (PET) was obtained by blending with 1-5wt% of a triblock copolymer with styrene end blocks and a func tionalized ethylene/butylene midblock. The midblock was grafted with 2 wt% maleic anhydride. The blends were characterized for melt viscosity , domain morphology, and tensile stress-strain behaviour at two strain rates. Blending increased the fracture strain of PET by more than a f actor of 10. The fracture strain was affected to some extent by both b lend composition and processing conditions. However, neither blend com position nor processing conditions strongly influenced the melt viscos ity of the blend or the particle size in the blend. These observations are consistent with in situ formation of a graft copolymer by reactio n of PET hydroxyl end groups with maleic anhydride. The graft copolyme r acted as an emulsifier to decrease the interfacial tension and reduc e the tendency of dispersed particles to coalesce, and promoted adhesi on between the phases in the blend. Evidence for the presence of a gra ft copolymer was obtained by i.r. analysis of blend extracts. (C) 1997 Elsevier Science Ltd.