Polyurethane elastomers made using mixtures of aliphatic diol chain extender and secondary amine

A process for preparing a noncellular or microcellular polyurethane elastomer, comprising 1) forming a reaction mixture containing a) one or more aliphatic diols having a hydroxyl equivalent weight of from about 30 to about 100, b) one or more secondary amine compounds having a molecular weight of 200 or less and at least one of c-1) and c-2), wherein c-1) includes one or more organic polyisocyanates having an isocyanate content of at least 15% by weight and one or more polyols having a hydroxyl equivalent weight of at least 250 and c-2) includes one or more isocyanate-terminated prepolymers or quasi-prepolymers having an isocyanate content of less than 15% formed in a reaction of an organic polyisocyanate with one or more polyols having a hydroxyl equivalent weight of at least 250 and 2) curing the reaction mixture in the presence of a catalyst to form the polyurethane elastomer, wherein:

• A) the reaction mixture contains no more than 0.25% by weight of a chemical blowing agent;
• B) the secondary amine compound contains one or two to four secondary amino groups, is devoid of primary amino groups, and the combined number of secondary amino groups and hydroxyl groups is from one to two;
• 3) the weight ratio of component a) to component b) is from 60:40 to 95:5;
• 3) the hard segment content of the polyurethane elastomer is from 30 to 60% by weight;
• and
• 4) the isocyanate index is from 70 to 125.