Influence of chemical curatives on the reaction between sulphur in silane and rubberphases in naturaltubber/polybutadiene blend reinforced with a silanised silica nanofiller

This study prepared a natural rubber/polybutadiene (NR/BR: 50/50 wt%) blend using precipitated amorphous white silica filler the surface of which had been pre-treated with bis-(3-triethoxysilylpropyl)-tetrasulphane (TESPT). TESPT is a sulphur-bearing bifunctional organosilane, which chemically bonds silica to rubber via the sulphur to form strong rubber-silica interaction. The rubbers were primarily cured by using sulphur in TESPT, and the cure was optimised by adding sulphenamide accelerator, zinc oxide activator and elemental sulphur. The chemical bonding between the sulphur in TESPT and the rubbers was affected mainly by the addition of the chemical curatives. In the absence of full chemical bonding between the sulphur in TESPT and the rubbers, most of the mechanical properties of the blend were inferior. But when chemical bonds or crosslinks fully formed between the sulphur in TESPT and the rubbers, the tensile strength, elongation at break, stored energy density at break, tear energy, cyclic fatigue life and abrasion resistance were enhanced. For example, the cyclic fatigue life of the blend increased by almost 50,000 times, which was a major improvement.