Optimization of Serial Modular Continuous Mixing Process Parameters for Natural Rubber Composites Reinforced by Silica/Carbon Black

Abstract

In the tire industry, the combination of carbon black and silica is commonly utilized to improve the comprehensive performance of natural rubber so as to realize the best performance and cost-effectiveness. The corresponding mixing is divided into three processes (initial mixing, delivery, reactive mixing) by the serial modular continuous mixing method, thus achieving more accurate control of the mixing process, higher production efficiency and better performance. Moreover, the optimization of serial modular continuous mixing process parameters can not only improve the performance of composite materials, but help people understand the physical and chemical changes and the reinforcing mechanism of fillers in the mixing process. In this paper, the relationship among the parameters of eight processes and filler network structure, tensile strength, chemical reinforcing effect and tear resistance was explored through experiments. The deep causes of performance changes caused by parameters were analyzed. Consequently, the best process condition and the ranking of the influencing factors for a certain performance was obtained. Furthermore, the best preparation process of natural rubber (NR)/carbon black/silica composite was achieved through comprehensive analysis.In modern industry, batch internal mixers are usually utilized to prepare carbon black/silica/rubber composite materials. After the first stage of mixing and dumping, the second stage of mixing is needed in order to realize a sufficient silanization reaction and control the heat load of rubber mixing. However, achieving acceptable performance also wastes energy and time [13][14][15][16][17][18][19]. In recent years, many scholars and companies have contributed to developing continuous mixers, such as the Farrell continuous mixer, the twin-shaft continuous mixer, the Buss Kneader continuous mixer, and the co-rotating twin screw continuous mixer [20][21][22][23]. Nevertheless, due to the structural limitations of the feeding port of the above continuous mixers, only powdery and granular materials are able to be added, except for block rubber. As a result, these continuous mixers are mostly applied in the plastic industry [24][25][26][27][28]. In addition, even though granular rubber is used as the raw material regardless of cost, the accuracy of the ratio of raw rubber and filler is hard to ensure with these continuous mixing methods. Consequently, based on the requirements of modern industrial continuous rubber mixing, a serial modular continuous mixer (SMCM) has been designed by Professor Wang [29]. The modular design ensures the accuracy of the ratio, and also has a good residence time, temperature control, and exhaust. The core components are the initial mixing rotors and the core reaction mixing twin rotors. The special geometry causes these components to produce elongational forces except shear stress to the compound, which enhances the dispersion effect and reaction extent. Previous studies have shown that, compared to two-stage mixing, the serial process ...

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