Efficient preparation of coal-series kaolinite intercalation compounds via a catalytic method and their reinforcement for styrene butadiene rubber composite

Abstract

A series of coal-series kaolinite intercalation compounds were efficiently prepared via a catalytic method. The efficiently prepared intercalation samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The intercalation ratio (IR) of kaolinite-dimethyl sulfoxide increased from 53.3% to 70.9% through the introduction of an inorganic acid. The intercalation time of kaolinite-methyl alcohol compound sharply decreased from 336 h from 12 h, and IR significantly increased from 9.2% to 41.8%. The kaolinite-stearic acid intercalation product was successfully and efficiently prepared through three rounds intercalation based on the kaolinite-dimethyl sulfoxide and kaolinite-methyl alcohol compound. The intercalated kaolinite particles had a physical dispersion in styrene butadiene rubber (SBR) matrix. The scorch time (t10) and curing time (t90) of the filled SBR composites decreased simultaneously relative to pure SBR, but the minimum torque and maximum torque presented no obvious change. The kaolinite-stearic acid intercalation gave a progressive reinforcement on mechanical properties of the filled styrene butadiene rubber composite. The tear strength and tensile strength of the SBR composite filled by kaolinite-stearic acid intercalation compound at 50 phr loading were 28.3 kN/m and 8.7 Mpa, respectively. The reinforcement of mechanical properties of the filled SBR composite is attributed to the fine dispersion of kaolinite lamellar-like structure in rubber matrix with restriction for rubber chains motion via trapping rubber chains in the house-of-cards structure and strong interaction with rubber chains via surface functional groups.