The physical and morphological properties of heterogeneous mixtures of polystyrene with styrene: butadiene copolymers were determined. A mechanism of ultimate failure is proposed which permits the qualitative rationalization of the effects of copolymer composition, structure, and concentration upon certain physical properties of the mixture.

In polymerization of vinyl chloride monomer, free radicals precipitate on or within aggregatm of partidy swollen dead polymer. Polymerization on the solid polymer is characterized by autoaccelerating rates due to a progressive reduction in termination rate.This reduction in termination rate is due to the fact that as the reaction progresses and more polymer accumulates there is a decrease in probability that chain transfer of polymer radicals to monomer will generate a mobile radical, which can readily terminate an occluded or stuck free radical. From the appearance of the particles of solid polymer in the system, it has been concluded that free radicals precipitate both on polymer particle surface and inside the open structure of polymer particles.

During the past decade, the application of microscopical methods and associated techniques has contributed much to the knowledge of heterogeneous polymer systems. Plasticized polymer, pigmented polymer, and polymerpolymer systems have all been examined successfully by the microscopical technique. Many of these hybrid polymer systems were developed, manufactured, and used extensively, long before any clear understanding of the mechanisms involved in their compounding was obtained. This discussion will bring together some of the technological details of the role of the microscope as it aids our understanding of heterogeneous polymer systems and the morphology — performance relationship of these materials.

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