Water resistance of polyurethane

Water resistance polyurethane elastomer has good water resistance at room temperature, and will not have obvious hydrolysis within one or two years, especially polybutadiene type, polyether type and polycarbonate type. Through strengthening water resistance test and extrapolation method, it can be concluded that the time needed for half of the tensile strength loss in 25 ℃ normal temperature water is 10 years for polyester type elastomer (poly (ethylene glycol adipate propylene glycol ester) - tdi-moca) and 50 years for polyether type elastomer (ptmg-tdi-moca), that is, 5 times for polyether type.

The water resistance of polyester polyurethane elastomer is not good. With the progress of hydrolysis, the acid value in the system increases gradually, which in turn promotes hydrolysis. But adding carbodiimide can improve the water resistance of polyester elastomer. The hydrolysis resistance of polyurethane elastomer vulcanized by isocyanate and 3% polycarbondiimide was compared. The sample with carbodiimide was immersed in water at 40 ℃ for one year, and its physical properties were almost unchanged. Therefore, it is possible to prepare ester polyurethane which can match the water resistance of ether polyurethane through the selection of polyester raw materials and the addition of water repellent polycarbondiimide.

The polyurethane elastomer made from polybutadiene polyol has the best hydrolysis resistance.