ORIENTED PP-PS COMPOSITES OBTAINED BY POLYMERIZATION OF STYRENE INSIDE ORIENTED PP MATRICES .1. DISPERSION OF PS AND THE COMPOSITES ORIENTATION

Dispersion of polystyrene (PS) and the molecular orientation of the po lypropylene-polystyrene (PP-PS) composites acquired by the in situ pol ymerization of styrene in the oriented PP matrices were characterized by microscopic observations, birefringence measurements, and different ial scanning calorimetry. It has been shown that applied processing of the ''envelope'' polymerization leads to obtaining oriented composite s with large contents and the specific dispersion of PS. Some composit es exhibit a substantial gradient of PS concentration and a gradient o f molecular orientation, both strongly dependent on the initial struct ure of the oriented PP matrix. The modification of the PP structure ta king place during processing does not disturb the orientation of the m atrices deformed to the higher draw ratios. The structural changes of the oriented PP induced by processing are reflected in the shrinkage b ehavior and mechanical properties discussed in the second part of this paper. (C) 1993 John Wiley & Sons, Inc.