Comparative Performance and Modification of Rubber and Reinforcing-Filler on the Tearing Resistance of Peroxide-Cured Natural-Rubber/Silica Compounds

Hypothesis: 

To enhance the crack growth resistance of rubber composites one strategy is to embed mechanisms for viscoelastic dissipation. This can be fulfilled by enlarging the bound rubber content through either increasing the filler-filler or filler-polymer interactions. Improving the filler-polymer interaction through surface modification of silica by silanes is not a favorable route because of the adverse impact of surface modification on lowering the share of filler-filler interaction on the bound rubber content. Modification of the rubber backbone appears to be a proper alternative. The difference in the .performance of these two methods can be observed well in peroxide-cured rubbers

Present contribution performs a comparative study on the impact of modification in rubber or reinforcing silica on the crack growth resistance of peroxide-cured natural rubber (NR). For NR/silica composites, the modifications in rubber and silica are respectively conducted by grafting maleic anhydride or the bi-functional silane of bis(triethoxysilylpropyl)tetrasulfide (TESPT). For the case of maleic anhydride grafting, the influence of initiation by thermal and chemical routes is also compared

Results revealed that the modification of the rubber with maleic anhydride leads to an increase in the polymer-filler interactions and the bound rubber content. This imparts a favorable balance in mechanical strength and resistance to crack growth of the resulting composite. Tearing resistance of the system containing maleated rubber in the high loading range of silica showed a significant increase of about 150% compared to a neat rubber system filled with unmodified silica. It was suggested that the chemical crosslink density and viscoelastic dissipation are, respectively, the controlling mechanisms of tear resistance in low and high loading range of silica.