Nonsolvent-assisted surface modification of silica by silane and antioxidant for rubber reinforcement

Abstract

Abstract To improve the reinforcing efficiency of silica (SiO2) nanoparticles for rubber and make the treatment procedure easy to commercialize in industrial level, antioxidant 2, 2′-methylenebis (6-tert-butyl-4-methyl-phenol) (2246) and silane were utilized to modify SiO2 via a nonsolvent-assisted process. Antioxidant 2246 was chemically grafted on the surface of SiO2 with the aid of silane coupling agent and performed better than free antioxidant in protecting rubber from thermo-oxidative aging due to the elimination the so-called “blooming” defects. Moreover, the antioxidant and silane modified SiO2 (SiO2-s-2246) was much better than modified SiO2 (m-SiO2) only by silane and unmodified SiO2 in dispersion and compatibility with styrene-butadiene rubber (SBR) based on the results of electron microscope observations, contact angle and bound rubber. Therefore, SBR/SiO2-s-2246 composites exhibited higher mechanical strength than SBR/m-SiO2 or SBR/SiO2 composites. For instance, SBR/SiO2-s-2246 composites with better elasticity exhibited an increase of 48% in tensile strength compared with SBR/m-SiO2 composites. The reinforcing mechanism of SiO2-s-2246 and m-SiO2 was also investigated based on the large strain behavior and swelling Gibbs free energy of SBR composites, which may be instructive for the rational filler surface modification.