| Precipitated silica is an important reinforcing agent used in rubber industry inferior to carbon black, but because of serious agglomeration and poor dispersity when filled in rubber, and its production process is complex, so do the cost, that’s why only filling precipitated silica is not enough, so another filler is needed. The kaolin resources is very rich in our country, relatively inexpensive, and its unique slice layer structure and surface properties decide it is a perfect reinforcing filler with precipitated silica for reinforcing rubber.This paper researched the effect of reinforcing BR/SBR rubber with modified precipitated silica and modified kaolin alone and together respectively. Research found that the modification conditions, process and vulcanization formula when filling BR/SBR rubber with precipitated silica and kaolin alone was not suitable for the situation of filling together.When filling BR/SBR rubber with modified precipitated silica and modified kaolin together, the suitable modification condition was as following, H12%, M52%, Z31%, modification temperature100℃, modification time10min. The suitable vulcanization formula of the kaolin/precipitated silica/BR/SBR composite was as following, R215phr, A13.0phr, A22.0phr, F1.0phr, P31.0phr, P50.5phr, filler90phr, S1.5phr, vulcanization temperature140℃, vulcanization time8min. The best ratio of modified precipitated silica and modified kaolin is1:1. When filling90phr fillers, the tensile strength of kaolin/precipitated silica/BR/SBR composite reached11.32MPa, elongation at break reached836.10%, tear strength reached48.94KN/m, hardness reached62HA. Elongation at break to836.10%, tear strength48.94KN/m, hardness of62HA. The comprehensive physical and mechanical properties of the composite could reach the national standards of pneumatic tire tube, truck tire, agricultural tire tube and three kinds of soft sole. After aging for48h, The comprehensive physical and mechanical properties of the composite tended to be stable, which could reach the national standards of pneumatic tire tube, truck tire and agricultural tire tube. Zeta potential, FT-IR, SEM and TG-DSC were used to analyse the mechanism of reinforcing rubber by kaolin and precipitated silica. Zeta potential analysis found that the higher absolute value of Zeta potential, the better reinforcing results. The zeta potential of powder could be improved through modification by coupling agent or lower the particle size of the powder. FT-IR analysis confirmed the mechanism of coupling agent with powder was that the coupling agent first formed the hydrolysis hydroxyl, and then bonded with the surface hydroxyl of powder. In vulcanization process, parts of inner hydroxyl of kaolin bonded with rubber chemically, and the addition reaction might occur between parts of double bonds of the matrix with inorganic. SEM analysis found that compatibility was extremely good between BR and SBR, but the mechanical performance of BR/SBR is poor when there isn’t any filler. On the one hand, surface modification made the powder surface organic, and improved the compatibility of powder with matrix; on the other hand, it played a role of strip milling, and decreased the stacked slice layer. The inorganic powder whose particle size was less than1~2μm could compatible well with rubber, and its phase interface was fuzzy, which had a good reinforcement effect. The shape characteristics of kaolin and precipitated silica were flake and granular respectively, which could achieve a certain synergy reinforcing effect when blending them together. TG-DSC analysis found that chemical bonds occured between coupling agent with inorganic mineral and rubber polymer, which made thermal decomposition of composite more slowly and complex, and improved the thermal stability performance of kaolin/precipitated silica/BR/SBR composite material effectively. |
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