Addition of DCP into NR/PS blends of 60/40 compositions caused an increase in the degree of crosslinks within the NR phase and at the NR-PS interface. The crosslink formation which normally occured quite fast in the early stage of blending was delayed on addition of LNR. Increasing the amount of LNR prolonged the induction period and decreased the blend viscosity. At the composition of 60/40 NR/PS, the optimum amount of DCP to yield maximum physical properties is 0.5-0.7 phr, and 5-7 % LNR respectively. The effect of LNR was not significant in improving the physical properties of blends with higher plastic contents.