Heat resistant styrenic polymer blends

A rubber modified styrenic polymer blend comprising:

• A. from about 25 to about 90% by weight based on the total weight of the blend of a fumaronitrile-containing matrix phase styrenic copolymer having polymerized therein,
• i. from about 45 to about 95% by weight, based on the total weight of the matrix phase copolymer, of styrene,
• ii. from about 5 to about 30% by weight, based on the total weight of the matrix phase copolymer, of fumaronitrile, and
• iii. from about 0 to about 25% by weight, based on the total weight of the matrix phase copolymer, of acrylonitrile;
• and
• B from about 10 to 75% by weight based on the total weight of the blend, of a grafted elastomer component comprising:
• a. from about 5 to about 45% by weight based on the total weight of the blend, of a grafted/or occluded binary copolymer having copolymerized therein:
• i. acrylonitrile, for compatibility with the fumaronitriile-containing matrix phase styrenic copolymer, in an amount, based on the total weight of the binary copolymer, between y % and x % wherein:
• y=(AN % in copolymer A+FN % in copolymer A), and
• x=(AN % in copolymer A+1.3.times.FN % in copolymer A)+7 and
• ii. styrene in an amount constituting the balance of said binary copolymer;
• and
• b. an elastomer substrate which constitutes 5-30% by weight of the total weight of the blend.