Abstract: A styrenic copolymer composition having increased resistance to heat, markedly improved impact resistance and excellent processability for injection molding, extrusion, thermal formability and the like is made by the polymerization of a vinyl aromatic monomer and an ethylenically unsaturated dicarboxylic acid moiety in the presence of at least two different rubbery additives. At least one, but not all of the rubbery additives consists of a copolymer of from 40 to 95% by weight of a vinyl aromatic monomer and 5 to 60% by weight of a conjugated diene monomer. This admixture permits addition of up to about 40% or more by weight of the total product of the rubbery additives. The properties achieved offer an attractive balance found only in higher priced engineering polymer materials. The polymerization process is preferably continuous and of the free radical type.

Abstract: A molding composition having advantageous toughness and impact resistance is prepared by polymerizing a mixture of styrene and maleic anhydride in the presence of and adapted to incorporate from about 5 to about 25% of a high impact polystyrene containing from about 4 to about 16% rubber, said high impact polystyrene having an average molecular weight which is significantly higher than the average molecular weight of the completed molding composition. The composition is especially useful in molding fiber-reinforced articles. The composition has outstanding toughness when green. That is, hot and freshly molded articles can be removed from the mold with minimized breakage, thus decreasing the amount of scrap arising from the breakage of a green molded item at the time of being ejected and/or removed from a mold. Moreover, the composition is moldable throughout a wide range of conditions and is less sensitive to changes in molding conditions.