Morphology and Viscoelastic Properties of Poly(Vinyl Chloride)/ Poly(Vinyl Alcohol) Incompatible Blends

The effects of the pre-mixing method and degree of saponification poly(vinyl alcohol) (PVA) on the morphology of poly(vinyl chloride) (PVC)/PVA blends were investigated. Two pre-mixing methods were employed: a powder method and an aqueous solution method. In the powder method, both components were blended in powder form before melt kneading using a mixing roll. In the aqueous solution method, the PVC powder was added to an as-prepared PVA aqueous solution, followed by drying and then pounding before melt kneading. In the case of PVA with a degree of saponification of 98 mol%, PVA domains several hundred μm across were dispersed in the PVC matrix in the powder method system, whereas finer PVA domains with sizes ranging from sub μm to several μm were observed in the aqueous solution method. In the cases of PVA with saponification degrees of 88 and 78 mol%, domain sizes of several tens of μm were observed for both powder and solution methods. This indicates that there was no apparent influence of pre-mixing method on the domain size. When poly(methyl methacrylate) (PMMA) was added to the PVC/PVA blend, smaller PVA domains (with sizes ranging from 5 to 10 μm) were observed in both powder and solution method systems than without the PMMA. Viscoelastic properties showed specific interactions between PVC and PMMA, and between PMMA and PVA.