The Processing and Performance of PVC Blends

Two grades of ethyl‐vinyl acetate copolymers (EVA), containing 26% vinyl acetate (VAc) (unmodified with 1.2% methacrylic acid), and 27% VAc (unmodified) respectively, and an ethylene‐vinyl acetate‐carbon monoxide terpolymer (EVA‐CO), were independently blended with two grades of polyvinyl chloride (PVC). The performance of these blends were also compared to several conventional plasticised PVCs (pPVCs), to determine the advantages of using these polymer‐modified PVCs as potential alternatives to the traditional plasticized PVCs for medical device and healthcare applications. Mechanical analysis of the EVA and EVA‐CO blends showed that the tensile and flexural modulus decreased significantly and impact strength greatly improved, with increasing copolymer and terpolymer content respectively. DMTA showed a shift in glass transition temperatures (Tg) of the PVC and EVA components for the PVC/EVA blends, suggesting partial miscibility over the range of concentrations studied. DMTA for the PVC/EVA‐CO blends showed a single Tg between that of the PVC and EVA‐CO components indicating complete miscibility. Rheological analysis gave only slight changes in shear viscosity with increasing copolymer and terpolymer content. The properties of most of the PVC/EVA‐CO blends were similar to those of commercially available plasticised PVCs suggesting these blends may be suitable alternatives to pPVCs, where improved impact strength is required particularly in medical film applications.