Effect of Silane Treatment Methods on Physical Properties of Rice Husk Flour/Natural Rubber Composites

In this study, the effect of silane treatment methods on cure characteristics and mechanical, dynamic mechanical, and morphological properties of rice husk flour (RHF)/natural rubber (NR) composites was investigated. The RHF surface was pretreated with alkali solution and then treated with bis(triethoxysilylpropyl) tetrasulfide (TESPT) solution using the unwashing silane treatment method and washing silane treatment method. The expected difference between these two methods was the silane layers presented on the RHF surface. Unwashed TESPT-treated RHF (UW-ST) and washed TESPT-treated RHF (W-ST) were incorporated into NR to prepare RHF/NR composites. 'I he TESPT molecules deposited on UW-ST and W-ST surfaces were confirmed by the additional peaks appeared in the FTIR spectra of UW-ST and W-ST. In addition, the decrement of decomposition temperatures and the changes in the residue amounts of UW-ST and W-ST proved the removal of the physisorbed silane layers after washing. The presence of TESPT molecules on the RHF surface enhanced compatibility and adhesion between RHF and NR matrix. This was confirmed by SEM micrographs of both UW-ST/NR and W-ST/NR composites. This result was also supported by the improvement of the mechanical and the dynamic mechanical properties of these two composites. According to mechanical properties of the NR composites, the washing silane treatment method was more effective than the unwashing silane treatment method for compatibility improvement between RHF and NR. The modulus, tensile strength, and tear strength of W-ST/NR composites can be enhanced without deterioration of their elongation at break.