Physical properties of poly(vinyl chloride) -copolyester thermoplastic elastomer mixtures

Abstract

A study has been made on the compatibility, thermal behavior, and mechanical properties of the system poly(vinyl chloride) and a copolyester thermoplastic elastomer (under the trade name of Hytrel by duPont). Results from NMR, linear thermal expansion, tensile test, and dynamic mechanical measurements indicate extensive mixing of PVC and the soft segments of the thermoplastic elastomer when the mixture is rapidly cooled from around 150 °C to ambient temperature. The hard segments of the elastomer crystallize under these conditions, as revealed by the calorimetric measurements. Upon isothermal annealing at 130 °C the mixture shows signs of phase separation in dynamic mechanical measurements. These observations suggest the existence of upper critical solution temperatures for the system. The associated miscibility gap encompasses room temperature and reaches a maximum temperature somewhere between 130 and 150 °C. The phase domains in the annealed sample are extremely fine and have been estimated to be no more than 100 Å in size from the pulsed NMR data.