Gas permeation of polymer blends. V. Compatibility studies of poly(vinyl chloride)/poly-ε-caprolactone blends

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Abstract
The transport behavior of O2 and N2 was studied for physical blends of Poly(vinyl chloride) (PVC) with poly-ε-caprolactone (PCL) and four types of ethylene-vinyl acetate copolymers and acrylonitrile-butadiene copolymers in which vinyl acetate and acrylonitrile contents were varied. Crystallinity of the blends was studied by x-ray diffraction at room temperature. Permeation rates of O2 and N2 measured at 25°C showed linearity in Arrhenius plot of permeability vs. PCL content in the blends. The same results were observed for the copolymers with varying comonomer contents. This indicates that the PVC/PCL blends form a compatible system. Rates of gas permeation for the blends decreased at PCL content lower than 30 wt %. This is due to the formation of a separate crystallized PCL phase in the blends. Part of the PCL component was still in the amorphous PVC/PCL mixed phase, which indicates strong molecular interaction but limited solubility. The observed linear relationship in the Arrhenius plot was discussed on the basis of the cooperative segmental relaxation process between PVC and PCL chains.