Functional rubber composites based on silica-silane reinforcement for green tire application: the state of the art

Abstract

Silica is the rubber industry’s most essential and cost-effective reinforcing filler after carbon black. The silica reinforcement mechanism with a non-polar elastomer is complicated by the presence of polar functional groups on the silica surface. This polar nature of silica causes filler-to-filler interaction by forming hydrogen bonds. Therefore, sizeable non-dispersed silica clusters remain in a non-polar rubber matrix. To avoid these strong filler-filler interactions and improve rubber/silica compatibility, the silica surface needs to be modified. This can be done using a coupling agent which has functional groups capable of linking both the rubber and silica. It has been discovered that when silica/silane coupling agents are present, the critical properties like rolling resistance and wet grip in the magic triangle of tire tread balance out better than carbon black formulations, bringing the system closer to the green tire goal. In this review article, the efforts made by both the rubber formulation development and chemistry to fully exploit the potential of silica/silane reinforcement for automotive tires are retrospected. Highlights on how compounding ingredients, process technology, functionalized elastomer, novel silanes, and the variant of silicas can enhance the magic triangle and silica-silane reaction mechanism are provided. In addition, the kinetics of silanization and measurements for the degree of silanization is also highlighted. Future research directions in this area are also touched upon. Hopefully, this review can stimulate future silica/silane scientific and technology developments for both academic and industrial-oriented requirements.

Effect of demineralized water on the silanization reaction and the performance properties of green tire tread compound

“…Better filler dispersion and better-silanized compound in the presence of water enables the formation of more linkages, such as a covalent bond between the filler and rubber after vulcanization, preventing the rubber from chipping under pressure. 14,53 However, a huge improvement in abrasion resistance is not possible as the chemical composition and silane concentration is the same in all the compound.…”

“…This hysteresis significantly influences tire performance, affecting the tire's grip and heat generation. 14 Although silica and silanes have been used for a few decades, the actual kinetics were unclear until Nishiyama et al 15 studied the hydrolysis and condensation mechanisms of a silane coupling agent based on the time-dependent behavior of 13 C and 28 Si nuclear magnetic resonance (NMR) analysis. The rate of hydrolysis and condensation depends on the water content present on the silica surface.…”

“…Hysteresis loss in rubber compounds, which can be predicted using viscoelastic theory, varies with ambient temperature and frequency. This hysteresis significantly influences tire performance, affecting the tire's grip and heat generation 14 …”

Nylon 66 short fiber reinforcement in EPDM power transmission belting: A path to enhanced mechanical performance

“…Aspect ratio, fiber length, orientation, dispersion, concentration, and adhesive treatments decide the mechanical and rheological properties of the rubber compound. [6][7][8][9][10][11] Up to 6 mm length short fiber-loaded composites augment stiffness and thermal stability. 12 Due to the high dry heat resistance requirements in the under-bonnet applications, EPDM is gaining momentum in place of chloroprene rubber (CR) in most automotive V-ribbed belt applications.…”

Microstructure and Performance of Green Tire Tread Based on Epoxidized Solution Polymerized Styrene Butadiene Rubber and Epoxidized Natural Rubber

“…The surface of silica consists of a large amount of polar silanol groups, so the high surface energy and strong filler–filler interaction lead to easy aggregation of silica nanoparticles, and the weak filler–rubber interaction results in poor compatibility between SSBR and silica. − Therefore, improving the dispersion of silica in a nonpolar matrix is necessary to obtain the high-performance silica/SSBR nanocomposites.…”