In situ compatibilization of polyurethane with poly(ethylene terephthalate)

Melt-mixed blends of a polyester type polyurethane (PU) with poly(ethylene terephthalate) (PET) were characterized by tensile testing, dynamic mechanical analysis, optical and electronic microscopy and solution 1H-NMR. Mechanical and thermal properties indicated good blend compatibility typical of a polymeric alloy. Morphology examination revealed good dispersion and strong interface adhesion. 1H-NMR of blends showed the formation of a PET-PU copolymer by ester–amide interchange reaction whose extent depended on the PET/PU ratio and melt mixing conditions. This in situ formed copolymer is responsible for the reactive compatibilization observed.