Carbon Black Filled Powdered Styrene-butadiene Rubber: Preparation, Structure And Property

The preparation of carbon black filled powdered rubber composite by simple latex/carbon black mixing method usually requires the addition of emulsifier to improve carbon black dispersion state in water(P(SBR/CB-E)). Addition of emulsifier enables carbon black disperse in water and rubber matrix in a more stable state, with smaller particle size and narrower particle size distribution. But most of the emulsifier remains in the surface of carbon black and in the rubber matrix and is hard to remove, resulting in the impairment of rubber-filler interaction thus affecting the performance of rubber vulcanizates, as known as weakening in stretching strength and abrasion resistance.In this paper, an improved process was developed for the production of carbon black filled powdered SBR without addition of emulsifier(P(SBR/CB)) by simple latex/carbon black mixing method. Compared to P(SBR/CB-E), although the dispersion of carbon black was slightly reduced, good vulcanizates performance was obtained due to good sustainment in rubber-filler interaction. A series of P(SBR/CB) composites were prepared covering wide ranging of carbon black loading(45 to 70 phr)and aromatic oil contents(0 to 30 phr). The influence of carbon black and aromatic oil content on the curing property, tensile and tear strength, compression behaviors and abrasion resistance of P(SBR/CB) composites were investigated and compared with dry mixing SBR/CB composites. It was found that tensile and tear strength of P(SBR/CB) vulcanizates were at the same level with SBR/CB vulcanizates, but P(SBR/CB) vulcanizates showed better dynamic mechanical performance, such as better compression fatigue resistance and abrasion resistance, than SBR/CB vulcanizates.It was found that the processing of P(SBR/CB) is in fact a process of carbon black dispersion in rubber and rubber-filler interaction, molecular weight of SBR molecule changes little. Due to good pre-dispersion in the rubber matrix of P(SBR/CB), carbon black dispersed much faster in P(SBR/CB) than in SBR/CB, and the dependency of mixing on carbon black content of P(SBR/CB) was lower than that of SBR/CB. The addition of aromatic oil could reduce the apparent viscosity and temperature rise of mixing for both rubber compounds, but it had little influence on carbon black dispersion rate in rubber.Mooney viscosity, bound rubber content and Payne effect of P(SBR/CB) increased upon storage, causing the hardening effect of P(SBR/CB). But after sufficient mastication, the storage stability of P(SBR/CB) increased, as shown as little change in bound rubber content during storage. This is because that filler-filler interaction and rubber-filler interaction of P(SBR/CB) was close to balance after mastication, resulting in improvement in the storage stability of P(SBR/CB).