Effects of slane coupling agent on in SITU silica reinforcement of natural rubber by sol-gel reaction in latex

Abstract

Modified silica was generated in NR matrix by a sol-gel process of tetraethoxysilane (TEOS) as a silica precursor in the presence of bis-(3- triethoxysilylpropyl) tetrasulfide (TESPT) as a coupling agent. The sol-gel process carried out in the concentrated NR latex, which was completed within 7 days at 50°c. The silica particles were well dispersed in the NR matrix and the particle diameter was in a submicron range. The influences of the amount of TEOS, TESPT and ammonia on the mechanical properties of the composites were investigated by a statistical analysis of the ‘two-level factorial design’ experiment. It was found that its tensile modulus at 300% elongation, tear strength and hardness were affected by the TEOS and TESPT content. There was no need to add more ammonia to the concentrated NR latex which contained 0.7% NH3. Moreover, the use of TESPT in the process increased the rate of sulfur vulcanization.