Assessment of the effect of a bifunctional organosilane on the bound rubber and properties of some natural rubber compounds

The effect of the coupling agent bis-(3-triethoxysilylpropyl) tetrasulphane (TESPT) on the properties of a filled natural rubber compound has been measured. The rubber was cured with a conventional accelerator and sulphur system, and contained silica particles. TESPT was added to prevent the silica from interfering with the reaction mechanism of sulphur cure in the rubber. This study showed that the hardness, cyclic fatigue life, cohesive tear strength, maximum tensile strength, elongation at break, and stored energy density at rupture were optimised when 7 phr TESPT was added to the rubber, whereas bound rubber was maximised with 5 phr TESPT. There was also evidence that the silica was poorly dispersed in the rubber and probably had not been properly silanised before addition to the raw elastomer. Interestingly, in spite of these inadequacies, there was consistency within the body of the work, and the trends observed were valid even though the full potential of the filler for optimising properties might not have been achieved.