Thermodynamic, viscoelastic and rheological structure-property relationships of rigid poly(vinyl chloride)-styrenic copolymer blends

Abstract

In order to extend low temperature properties, rubber modification of PVC is commonly employed. The upper use temperature is however still restricted. To counter this problem modification using higher glass transition polymers is reviewed. As opposed to using a high Tg polymer, copolymers are investigated with the aim of improving the net intereaction energy between the two systems. The polymers are a low molecular weight styrene acrylonitrile and a high molecular weight alpha methyl styrene acrylonitrile. The binary systems thus compose of two glassy polymers and they are reviewed for property improvement based on modulus-temperature curves as well as employing a time-acceleration scheme which hitherto has been primarily applied to single phase systems. Relationships between the activation energy (of the a transition)- composition and the storage modulus-temperature-composition relationships are examined to determine means to optimize the systems. Based on preliminary evidence of a marked solvent effect in the systems, departure from ternary solvent generated systems is ensured by using compression molded systems. The morphology of the compression molded samples is examined using the Scanning Electron Microscope and the Transmission Electron Microscope. Susceptibility to change in flow is also examined through the use of an Instron Capillary Rheometer and Parallel Plate Rheometer.