Speciality polymer blends of carboxylated nitrile rubber and polyurethane elastomers

Blends of polyurethane elastomers and carboxylated nitrile rubber, prepared by three different techniques in different blend ratios, have been studied. The properties of the blends were improved by blending with polyurethanes in a sulphur cured blend system. In the peroxide cure system the improvements occurred when the preblends were heated before incorporating curatives into it. Blend properties largely depend on the blend ratio and on the blending technique. IR spectra reveal that interchain crosslinking occurred between polyurethane and carboxylated nitrile rubber on heating, in the absence of curatives. The preheating of the blends before adding curatives improved the properties of the blends; the degradation process and weight loss were retarded. The extraction of the carboxylated nitrile rubber (XNBR) phase in the solvents was also restricted on preheating, due to interchain crosslinking.