POLYETHYLENE POLYSTYRENE BLENDS

Polyethylene-polystyrene (PE-PS) blends involving three samples of PS of different molecular weight were obtained. Blending was performed on rolling mills at temperatures and shear stresses chosen so as to ensure maximum dispersion of components but to avoid chain scission. Scanning electron microscopy, differential thermal analysis and X-ray diffraction were used to examine the supermolecular structures of the blends; density, viscosity and mechanical measurements were also performed. Depending on the composition and molecular weight of PS, the morphology of the blends changed between that of spherical domains of one component dispersed in a continuous matrix of the other, to a highly nonhomogenous mixture of fibrous or cabbage-like macrodomains of both components. The presence of PS disturbed the development of PE crystallites and caused decrease of the degree of crystallinity of PE with increase in the PS content (from 0.56 to 0.41 as the PS content increased from 0 to 80 wt%). Some nonadditivity of modulus of elasticity was investigated in terms of the Takayanagi Model I. © 1990.