Blends of thermoplastic polyurethane and polyether-polyimide: preparation and properties

A series of blends of thermoplastic polyurethane(PU) and polyether-polyimide (PI) were prepared in two steps. The first step was the preparation of polyether-amic acid by the reaction of an oligmer based on polytetramethylene oxide glycol di-p-aminobenzoate (APTMO) of different molecular weight (650, 1000, and 2000) with benzenetetracarboxylic acid dianhydride (PMDA). The second step was mixing polyether-polyurethane and polyether-polyamic acid solution at room temperature in various weight ratios, and the blend films were obtained by casting and then heat imidization. Infrared spectroscopy (IR), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), small-angle X-ray scattering (SACS) and wide-angle X-ray diffraction(WAXD) were used to study this family of blends. DSC analysis of the films showed that glass transition temperature (T-g) of PU-PI 650 and PU-PI 1000 series shifted depending on the ratio of PU and PI components. The shift of T-g, along with the transparency of the films, gave the evidence that soft segments of PU and PI were miscible to some extent in the PU-PI 650 and PU-PI 1000 series. DMA results indicated that the blends exhibited a well phase-separated structure and had a broad rubbery plateau from about -30 to 200 degreesC, which varied with the PU content. Thermal stability of PU was found to increase by the incorporation of PI. The excellent tensile properties of the blends suggested that they could be potentially used as heat resistant thermoplastic elastomers. (C) 2000 Elsevier Science Ltd. All rights reserved.