Active hydrogen compositions and thermally stable and high impact resistant structural polyurethane foams prepared therefrom

Molded cellular polymers are disclosed which are derived from the reaction of organic polyisocyanates with novel active hydrogen compositions comprising (A) a polyester polyol mixture derived from (i) an aromatic polycarboxylic compound containing two or more carboxylic groups; and (ii) an excess of at least one polyol having from 2 to 8 hydroxyl groups and an equivalent weight of from 30 to 250; and (B) from 5 to 30 percent by weight of a primary or secondary amine terminated polyether of greater than 1500 molecular weight and amine functionality of from 2 to 8. The molded products are characterized by a combination of excellent impact strength and resistance to high temperatures as well as good resistance to burning.