For a long time, in the production process of recycled rubber products, white carbon black is used in the production of white, light-colored and color reclaimed rubber products instead of carbon black. It creates a good foundation for the color matching of rubber products. Is it only white carbon black? Can it appear in the production of recycled rubber products as a "replacement"? What are the unique structural features and performance characteristics of silica, what should you pay attention to when using it?
For white carbon black, Baidu Encyclopedia is defined as: white carbon black is a general term for white powdered X-ray amorphous silicic acid and silicate products, mainly refers to precipitated silica, fumed silica and ultrafine Silica gel, also including powdered synthetic aluminum silicate and calcium silicate, can be divided into precipitation method white carbon black and gas phase white carbon black according to the production method, and mainly used as a reinforcing agent in the production of reclaimed rubber products.
The reinforcing effect of silica in the production of reclaimed rubber products is directly related to the particle size, structural characteristics and surface chemistry of silica. Generally, the larger the specific surface area and the smaller the particle size, the higher the activity of silica. It is more beneficial to improve the tensile strength, tear strength and wear resistance of the reclaimed rubber vulcanizate, but the elasticity decreases, the viscosity of the reclaimed rubber compound increases, and the processing performance decreases; the agglomerates formed by hydrogen bonding on the surface of the white carbon black More and stronger than carbon black, so high surface area, high structure of white carbon black will increase the regrind viscosity and hinder processing. When using white carbon black as a reinforcing agent in recycled rubber products, the type of white carbon black should be reasonably selected, the amount of white carbon black should be controlled, and the relationship between the mechanical strength of the recycled rubber and the elasticity of the rubber compound and the processing performance should be coordinated.
The surface groups and surface activities of the precipitated silica and the fumed silica are different. The surface of the precipitated silica and the fumed silica contain silanol groups, but the precipitated silica is somewhat acidic and some is alkali. Sexual and meteorological method, the surface of silica is acidic; in terms of hydrophilicity, the surface of the white carbon black has more microporous structure, better hydrophilicity and stronger hygroscopicity, which is in the reclaimed rubber of white carbon black. The reinforcing effect is very unfavorable. If the moisture is too high, the rubber will be scorched; a large amount of hydroxyl groups on the surface of the white carbon black will strongly adsorb the regenerated rubber vulcanization system in the rubber compound, thereby delaying the vulcanization. Therefore, in the production process of reclaimed rubber products, the precipitation method of white carbon black should be used with caution, and moisture prevention should be taken. It is preferable to use white carbon black (mainly modified white carbon black) which has been modified by a surface treatment agent.
In addition, the reclaimed rubber uses a white carbon black with a pH of 8 or more, and the vulcanization rate of the rubber is faster; the reclaimed rubber compound using a white carbon black having a pH of 5 or less has a particularly slow vulcanization rate, so the reclaimed rubber product manufacturer selects white carbon. In the case of black, it is necessary to select the appropriate type and suitable index of white carbon black according to actual needs, and add a certain proportion of active agent to the white carbon black to adjust the vulcanization efficiency of the recycled rubber product, and further improve the comprehensive performance of the finished product.