Broad line NMR investigation of compatibility using powdered and milled samples of PVC and EVA, and the effects of heat-treatment

The limited miscibility of poly(vinyl chloride) (PVC) and ethylene-vinyl acetate copolymer (EVA) observed for milled samples has now been demonstrated for samples in powdered form by means of broad line NMR. The changes in the phase relations are mainly dependent on two processes, viz. the phase separation and the development of the interactions between PVC and EVA chains. The stable level of the phase relations is dependent upon the thermal history. We assume this to be an effect of the varying degrees of entanglement between PVC and EVA chains. It has also been demonstrated that the fraction of EVA staying in the free phase increases both for the milled and powdered samples when the degree of grafting between PVC and EVA decreases. A method for the quantitative investigation of the solubility conditions of polymer two-phase systems in bulk is also presented.