Structural change and interfacial interaction in blended rubber composites filled with silica–kaolin hybrid fillers: A Fourier transform infrared spectroscopic study

Abstract

ABSTRACTThe aim of this study was to prepare rubber composites by reinforcing natural rubber/styrene butadiene rubber/polybutadiene rubber system with hybrid fillers composed of nanometer silica and micron kaolin, and figure out the structural changes and interfacial interactions in composites mainly by Fourier transform infrared spectroscopy. A series of composites were prepared by dry modification process, mechanical compounding, and mold vulcanization. Besides, X-ray diffraction and scanning electron microscope were also used for analysis of structural changes and morphological properties. The results showed that the coupling agents were mainly coated on silica particles rather than kaolinite surface because the reactive sites on kaolinite surface were limited and covered by silica particles when mixed. The structure order of kaolinite in composites was changed especially with the incorporation of silica particles due to the different shape of fillers, uneven loading force and the “seesaw” structure formed in the preparation process, which would be beneficial to the dispersibility of fillers in rubber matrix. Kaolinite in the composites was generally distributed in directional alignment. The particle size of fillers and the amount of modifiers used were supposed to influence the formation of the soluble sulfureted zinc complex and the effects of this complex on vulcanization. Kaolinite with smaller particle size and less defective structure was more stable in preparation, kaolinite with larger particle size and high-defect structure was potential to change crystal structure. The preparation process and composites with balance mechanical properties showed promising application in tread compound of agricultural tires.