Investigation of the effect of mixing schemes on rheological and physico-mechanical properties of modified natural rubber blends

In this paper, the effect of three different mixing schemes on rheological, crosslink parameter and physico-mechanical properties of vulcanizates from the blends of natural rubber (NR) and ELMWNR were reported. The compounding ingredients were mixed with the two mentioned rubbers using three different mixing schemes by adopting the semi-efficient sulphur vulcanization compounding formulation. In Scheme 1, the natural rubber and ELMWNR were first mixed before adding the compounding ingredients. In Scheme 2, the compounding ingredients were first mixed with the NR before adding the ELWMNR and in Scheme 3; the compounding ingredients were first mixed with the ELMWNR before adding the NR. The rheological and physico-mechanical results of the vulcanizates showed that changes in the mixing schemes significantly influence the cure rate and tensile properties of the rubber blends. The tensile strengths of the vulcanizates prepared with mixing Scheme 2 were 2 MPa lower than vulcanizates from Scheme 1, while Scheme 3 was lower than Scheme 1 with 5 MPa. Above all, the elongation at break and crosslink density of vulcanizate from Scheme 1 were found having the highest values, signifying a well crosslinked vulcanizates.