Two elastomers having reactive functional groups may react with each other. Considering this, the blends of PU and EPR elastomers have been prepared where better performance properties can be tailored and optimized through the interchain crosslinking reaction. It is evident from the IR spectral analysis of the thin film of PU/EPH blend without curatives that an interchain crosslinking reaction occurs between the two elastomeric phases. Preheating of the preblends before addition of curatives enhances the properties of the blends. Thermal study revealed the delayed degradation with retardation in weight loss for the preheated, preblended samples. Preheating also restricted the extractability of the phases, by solvent, due to interchain crosslinking. (C) 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1367-1376, 2000.