Compatibilization and properties of PBT/PU polymeric alloys

Melt mixed blends of poly(butylene terephthalate) (PBT) with a polyester type polyurethane (PU) were characterized by tensile testing, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), optical and electronic microscopy (SEM) and solution 1H NMR. Blends prepared covered the complete composition range. Large deformation behavior, thermal properties and DMA indicated partial component mixing and mechanical compatibility typical of a polymeric alloy. Morphology examination revealed good component dispersion and strong interface adhesion. 1H NMR of blends showed the formation of a PBT–PU copolymer by ester–amide interchange reactions whose extent depended on the PBT–PU ratio and melt mixing conditions. Evidence for the formation of the copolymer was also provided by FT-IR. This in situ formed copolymer is responsible for the compatibilization achieved.