Optimising the chemical bonding between silanised silica nanofiller and natural rubber and assessing its effects on the properties of the rubber

A small amount of synthetic precipitated amorphous white silica nanofiller was used to reinforce the properties of natural rubber (NR). The silica surfaces were pre-treated with bis[3-triethoxysilylpropyl) tetrasulphane (TESPT) to chemically adhere silica to rubber and also to prevent it from interfering with the reaction mechanism of sulphur-cure. The rubber was cured primarily by using sulphur in TESPT, or, by adding elemental sulphur to the cure system. The cure was optimised by adding sulphenamide accelerator and zinc oxide, which also helped to form chemical bonding between the filler and the rubber. The hardness, tensile strength, stored energy density at break, and compression set were improved when the filler was incorporated into the rubber. However, the tear strength, elongation at break, and cyclic fatigue life were adversely affected.