Effects of Surface Chemistry of Silica Particles on the Mechanical Properties of Silica Filled Styrene–Butadiene Rubber Systems

Abstract

ABSTRACT:The effects of surface chemistry of silica particles on the mechanical properties were studied for silica filled styrene-butadiene rubber (SBR) systems. The samples were prepared from different kinds of silicas and of silane coupling agents. The breakdown of the agglomerate formed by silica particles was successfully detected by transmission electron microscopy (TEM) observations when the strain was applied to silica filled vulcanizates. The degree of breakdown of the agglomerate of silica particles by the strain was more prominent in the larger one of which size was controlled by the number of silanol group per unit surface area of silica particles. The amount of entrapped rubber within the agglomerate seemed to be decreased with the decrease in the agglomerate size. Also, the initial agglomerate size and the change of agglomerate by the strain became small by the introduction of silane coupling agent, such as bis(3-triethoxysilylpropyl)tetrasulfane (TESPT). At a given degree of vulcanization, the initial modulus of silica filled vulcanizates was governed by the size of agglomerate formed by silica particles and the amount of entrapped rubber phase. On the other hand, at a larger strain, the tensile strength of the filled vulcanizates increased by the introduction of interfacial combination between silica particles and rubber matrix by TESPT. These results indicate that the stress-strain behavior of filled vulcanizate is affected by the agglomerate of the fillers and the interactions between filler and rubber matrix.KEY WORDS Silica / Styrene-Butadiene Rubber / Silane Coupling Agent / Transmission Electron Microscopy (TEM) / Agglomerate / Mechanical Properties / Silicas have been used as fillers for rubber reinforcement. 1-3 However, the utilization of silica caused two serious problems. One was a bad processability, such as a lower dispersiblity of silica particles in rubber matrix and a high viscosity of silica filled unvulcanizates. [2][3][4][5][6][7][8] The other one was a poor reinforcement, such as a low tensile strength, low abrasion resistance and so on, in comparison with carbon black filled rubber composites. [1][2][3][4][5][6][7][8] The chemical environment of silica particle is quite different from that of carbon black due to the existence of silanol groups in the particles. Thus, the primary discussion on the properties of silica filled rubber composites has been concerned with the interactions between silica particles and the interactions between silica particles and rubber molecules. Wolff and Wang studied the effects of surface energies of fillers on rubber reinforcement, and reported 7 that the surface energies of silica were characterized by a dispersive and specific components. The higher specific component led to the higher viscosity of the rubber composites due to the strong interactions among silica particles. On the other hand, the lower dispersive component caused weak filler-rubber interactions, leading to the lower † To whom correspondence should be addressed. content of bound...

Chain Scissions of Rubber Molecules by a Tensile Force in Filled Rubber Systems

“…It is well recognized that the stress-strain curves at a larger strain for filled rubber systems are affected by the crosslink density of rubber matrix 6,8) and rubber/filler interactions 8,18) . These factors can be controlled by the contents of curing agents and the introduction of coupling agent.…”

“…The rubber molecules which are anchored to filler particles will break if filler particles have separated enough to stretch the chain to near full elongation. Yatsuyanagi et al carried out transmission electron microscope (TEM) observations of silica filled vulcanizates before and after the tensile deformation 7,8) .…”

Possibilities of rice husk ash to be used as reinforcing filler in polymer sector -a review

“…Hydroxyl groups on silica surface could form very strong intermolecular hydrogen bonds with another hydroxyl of an adjacent silica particle. This hydrogen bonds causes the easily formation of tightly held aggregates which cause a poor dispersion of silica particles in a rubber matrix [81], [104], [105]. The hydrogen bonds also contributes to increase viscosity of WRHA/NR composite faster than most fillers specially those with high surface are.…”

Application of Acrylonitrile Butadiene Rubber for Management of Industrial Waste Silica

“…The explanation is given as the adsorption of zinc complex on the silica surface, thus lowering the sulfur vulcanization efficiency. (Table 3) Stress strain of rubber composite (Figure 2) (Table 4): It is well known that the stress-strain curves for silica filled rubber systems are affected by the crosslink density of rubber matrix [60,61], the size of agglomerates formed by the silica [62,63] and rubber / silica interactions [64,60]. These effects can be controlled by the contents of curing agents, the number of silanol groups on silica particles and the introduction of coupling agent.…”

“…Thus silica filled rubber systems are suitable for the investigation of chain scission of rubber molecules during the deformation. For silica filled rubber systems, the rubber/filler interactions can be controlled by the introduction of coupling agent [22][23][24].…”