Phase Behavior and Properties of Polyurethane-PVC Blends and Fibers

Abstract

Abstract A polyester urethane elastomer is blended with rigid poly(vinyl chloride) (PVC) and the miscibility of the components studied over the entire range of compositions. The polyurethane elastomer was a block copolymer with a low degree of crystallinity, while PVC was practically amorphous. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) methods showed that polyester urethanes were partially miscible with PVC since two distinct glass transitions, which changed with the change of concentration of components, were observed. Although the PVC content was varied from 0–100%, the aim of the work was to examine if PVC at low concentrations would form fibrils in the urethane matrix and act as a reinforcing agent for the polyurethane elastomer. The morphology of the blends was studied by scanning electron microscopy and x-ray scattering. The blends were then spun into fibers to force the dispersed phase to elongate and form fibrils (draw ratio was about 100). A high degree of miscibility is obtained at low concentration of either of the components. The PVC phase in fibers spun from the blends have higher glass-transition temperature (Tg) than in isotropic blends, presumably due to increased orientation. No fibrillation of the rigid phase in the elastomeric matrix could be observed. The fibers displayed higher strengths but lower elongation at break than the isotropic blends of the same composition. Intermeshing morphology (at about 50/50 concentration) gave the lowest strengths.