High-value application of kaolin by wet mixing method in low heat generation and high wear-resistant natural rubber composites

In this study, a silane coupling agent and kaolin, a natural mineral resource, were introduced into the wet mixing process of natural rubber latex, the high wear-resistant and low-generation heat natural rubber composites were prepared. The sputtering, collision, and deposition of coupling agent/fillers/natural rubber latex mixed emulsion onto the roller effectively could break up the filler aggregates, enable fillers to be better infiltrated, distributed, and dispersed in the rubber. The effects of dry/wet mixing processes and the ratio of kaolin to silica on the crosslinking density, filler dispersion, extrusion rheological properties, gas barrier properties, dynamic mechanical properties and thermal stability of NR composites were investigated, and the silanization mechanism was summarized by FTIR and XRD. The experimental results showed that kaolin improved the crosslinking density and failure temperature, reduced the Payne effect, extrusion swell, and rolling resistance. Compared with 60 phr silica-filled natural rubber, the gas barrier property and wear resistance of 60 phr kaolin-filled natural rubber were improved by 64 % and 27 %, respectively, and the rolling resistance was reduced by 57 %. When the ratios of silica to kaolin were both 20:40, the crosslinking density, gas barrier property, and wear resistance of wet mixing were improved by 24 %, 45 %, and 9 %, respectively, compared with dry mixing. This study provided a new method for the high-value application of kaolin in wet mixing and green tires.