Flexible polyurethane foam

A method of preparing a flexible polyurethane foam having a tensile strength greater than 2,5 kilograms per square centimetre comprises compressing for a period of from one to ten hours a polyurethane foam product of less tensile strength at a compression ratio in excess of 2:1 in the presence of water and at a temperature of 100 DEG C. to 120 DEG C. In an example polypropylene glycol and tolylene diisocyanate are reacted to give a prepolymer which is converted to a foam by reaction with water, N-methylmorpholine and triethylamine. Sheets of the product of thicknesses from 1 cm. to 2,5 cm. are moistened with water and then for 5 hours compressed to a thickness of 0,4 cm. in a press heated to 100 DEG C. Using compression ratios of 2,5, 3,75, 5,0 and 6,25, products are obtained (from material of tensile strength 1,5) having T.S. values of 3,6, 5,3, 7,9 and 9,6.ALSO:A method of preparing a flexible polyurethane having a tensile strength greater than 2,5 kilograms per square centimetre comprises compressing for a period of from one to ten hours a polyurethane foam product of less tensile strength at a compression ratio in excess of 2:1 in the presence of water and at a temperature of 100 DEG to 120 DEG C. In an example polypropylene glycol and tolylene diisocyanate are reacted to give a prepolymer which is converted to a foam by reaction with water, N-methylmorpholine and triethylamine. Sheets of the product of thicknesses from 1 cm to 2,5 cm. are moistened with water and then for 5 hours compressed to a thickness of 0,4 cm. in a press heated to 100 DEG C. Using compression ratios of 2,5, 3,75, 5,0 and 6,25, products are obtained (from material of tensile strength 1,5) having T.S. values of 3,6, 5,3, 7,9 and 9,6.