FORMATION OF GRADIENT PHASE-STRUCTURE DURING ANNEALING OF A POLYMER BLEND

The phase morphology of ethylene-vinyl acetate copolymer (EVAc) and polypropylene (PP) blends was studied. It was observed that a 70/30 blend of PP and EVAc having 33 wt% vinyl acetate formed a gradient phase structure in the cross-section by annealing. In other words, the particle size of the EVAc dispersed phase increased gradually along the direction perpendicular to the sample surface from the centre to the surface. The longer the annealing time, the more the particle size of the dispersed phase grew. The vertical distribution of the EVAc component was analysed using an image processor analyser and found to be inhomogeneous. The component increases along the vertical direction of the sample from the centre to the surface. This corresponds to the result of the particle size of the EVAc dispersed phase growing uniquely.