Silica-graphene oxide nanohybrids as reinforcing filler for natural rubber

Abstract

Hybrid silica-graphene oxide (SiO2@GO) nanocomposites were fabricated by sol-gel method using tetraethylorthosilicate (TEOS) as silica (SiO2) precursor. The prepared nanocomposites were characterized by various analytical techniques to prove that the SiO2 were completely incorporated on the GO surface. Then, the SiO2@GO nanocomposites were introduced into natural rubber (NR) matrix followed by conventional vulcanization process, performed by two-roll mill, to obtain NR/SiO2@GO vulcanizate. The results showed that the presence of SiO2 nanoparticles on the GO surface improved the distribution of GO in NR matrix, resulting in the increase in modulus and hardness. For comparison with neat NR, NR/SiO2, and NR/GO, the network parameters of vulcanizates were evaluated using swelling test and tube model theory contributed in stress-strain measurement. These exhibited that the SiO2@GO induced the chemical crosslink between NR chains, leading to the increment in crosslink density. It was because the well dispersion of SiO2@GO in NR matrix improved the volume fraction of rubber. Moreover, dynamic mechanical analysis was employed to determine the viscoelasticity behavior of the vulcanizates. The results showed that the presence of SiO2@GO in NR vulcanizate improved the storage modulus in all temperature range. That meant the elasticity of the vulcanizates was improved by the reduction of the viscous phase to stiff phase ratio of the material. However, the reinforcement of NR using SiO2@GO as filler was effective in lower deformation reflected from higher modulus at low strain. In addition, the modulus decreased in comparison with that of the neat NR under higher deformation until at break point. Thus, the tensile strength decreased while elongation at break increased. This phenomenon might be explained that the strain-induced crystallization of NR occurred under higher strain was reduced because the rubber chains alignment which was obstructed by the filler penetration and high number of chemical crosslinks. Therefore, the covalent hybrid SiO2@GO nanocomposites had potential for use as filler in engineering rubber composites that were suitable for the compressive or abrasive applications.