Effect of Interfacial Tension on the Formation of the Gradient Morphology in Polymer Blends.

In order to investigate the effect of interfacial tension on the formation of gradient phase morphology in polymer blends, a saponification reaction was carried out in this study to obtain several kinds of EVA with different contents of -OH groups. These EVAs with different -OH contents, namely with different polarities, were then blended with PP, and thus a series of PP/EVA blends with different interfacial tensions was obtained. The same initial droplet size could be obtained for PP/EVA blends with different interfacial tensions during compounding through adjusting the degree of saponification of EVA. It was found that all these PP/EVA blends could form a gradient morphology in the vertical section of the samples as PP/EVAc blends. Using a computer image analyzer, the vertical distributions of the dispersed droplet size and the EVAc component in each blend were determined. The results showed that the EVA droplet size and the EVA component increased in the vicinity of the sample surface with increasing interfacial tension of the blends; i.e., the greater the interfacial tension between PP and EVA, the larger the gradient tendency in the blend. Copyright 1998 Academic Press.