From Reports in Volume 5: "Recently polymer blends have emerged as one of the most important areas of research activity in the field of polymer science and technology. Because of their satisfactory performance in meeting specific needs of the polymer industry, they have drawn considerable attention in replacing not only many conventional materials, but also some of the polymers that are in vogue. By suitably varying the blend compositions and manipulating the processing conditions, tailor-made products with a unique set of end use properties can be achieved at a much lower cost and within a shorter time than would have been necessary for the development of a new polymer. The usefulness of such blends increases with the increasing range of applications of this type of materials." (Chapter 4) "New and growing demands on polymeric materials cannot be satisfied in future by an assortment extension of basic polymers. Although the introduction of new major-use basic polymer is possible, it seems unlikely in view of current projected economic and technical considerations. On the other hand, new products based on the modification of existing polymers have and will continue to be fruitful areas for both scientific and commercial developments. The driving forces for these developments are: 1. Improved performance, 2. Reduced cost, 3. Present, pending and future legislation dealing with health and environmental issues." (Chapter 11)

This study shows the impact resistance of polypropylene toughened by an ethylene-propylene elastomer. The objective was to modify polystyrene with linear thermoplastic elastomer of styrene-isoprene-styrene triblock copolymer and polystyrene with ethylene-propylene rubber by weight by melt blending.