Exfoliation, hydroxylation and silanization of two-dimensional (2D) montmorillonites (MMTs) and evaluation of the effects on tire rubber properties

Abstract

In this work, effects of two-dimensional (2D) montmorillonite (MMT) on physical/mechanical/dynamic properties and rolling resistance of a model tire rubber were assessed. To achieve proper performance of MMTs in rubber compound, the layered stacks were initially exfoliated using sonication in deionized water. Pure MMTs showed a great tendency to aggregation in rubber matrix due to their superhydrophilic nature, so they were functionalized using 5 M NaOH solution to create surface OH groups for subsequent modification. The functionalized MMTs were silane modified with vinyltrimethoxysilane (VTMS) at different concentrations, finally, vinyl groups caused hydrophobicity and increment of water contact angle (WCA) from 35° to 92° in comparison with pure MMTs. The performance of tire rubber blends (TRBs) containing the pure MMTs, exfoliated MMTs and silanized MMTs was compared to the pristine rubber. Silanization of MMT caused a 140.47 % increase in the crosslink density of TRB nanocomposite. The results showed that the optimum curing time of rubber decreased by 56 s compared to the pristine TRB. The modulus of 100 and 300 % increased by 103 and 20 % for sample that contained silane modified MMTs, respectively. The elongation at break decreased by 7 % for the modified nanocomposite compared to the pristine TRB. Also, the storage modulus and transition glass temperature of nanocomposite containing silanized MMTs increased by 54 % and 7 °C compared to the control TRB, respectively. The rolling resistance in the tire (i.e. C-s5-MMT1) demonstrates a prominent reduction of 19.42 %, accomplished with a 30.28 % decrease in power loss, 85.07 % Akron abrasion loss, and the lowest Heat-Build up, as compared with the pure tire (i.e. C-Ctrl).