The impact strength of RTR/HDPE blends increases with increasing RTR loading up to 50 pbw. This high impact strength is in the appropriate range for automotive application. Sulphur vulcanization was found to be the best method to produce the blend with the highest impact and tensile strength, while the peroxide curing method was the poorest. The mixed system provided the blend with the intermediate properties. Effective curing of the blend by sulphur or mixed system was shown by lower swelling ratio, higher viscosity, and higher Tg. The 50/50 RTR/HDPE blend using sulphur vulcanizing agent showed the highest Tg. The RTR/HDPE blend vulcanized by sulphur had the highest viscosity and storage modulus. By SEM, the morphology of the RTR/HDPE blends vulcanized with sulphur or mixed system showed more even dispersion of RTR particles in HDPE matrix.