Silica and modified silica fume waste (mSF) as reinforcing fillers for rubber industry

Abstract

Purpose The purpose of this paper is to evaluate the efficiency of commercial silica, silica fume-waste (SF) and modified silica fume-waste (mSF) as reinforcing filler in acrylonitrile-butadiene rubber (NBR) and ethylene propylene diene monomer (EPDM) through the mixing process of rubber. The composites were prepared using different loadings of silica fume and commercial silica in EPDM and NBR composites. Structural characterization of silica and SF was done using X-ray fluorescence and scanning electron microscopy (SEM). The surface of silica fume waste was modified using poly methyl methacrylate/butyl acrylate through emulsion polymerization to increase the interaction between silica and rubber, then consequently better dispersion in rubber matrix was obtained. The mSF waste was characterized using FT-IR spectra and transmission electron microscopy. Design/methodology/approach The investigated rubber mixes and vulcanizates were evaluated by measuring the curing characteristics, mechanical testing, thermogravimetric analysis and morphological studies (SEM). The mechanical properties of composites including tensile strength, elongation at break and modulus were estimated and analyzed. Findings The results revealed that the composites (NBR and EPDM) containing mSF as filler exhibited better rheological and mechanical properties compared to unmodified silica waste and commercial silica. The SEM analysis indicated that the mSF was homogeneously dispersed through the surface of NBR and EPDM composites. Also, results showed that (NBR and EPDM) composites exhibited remarkable improvements in tensile strength, elongation at break and hardness in the presence of mSF; they also showed an increase in the thermal stability. This means that the treatment of surface SF can improve its dispersion in rubber. Research limitations/implications Silica cannot be applied in rubber matrix without surface modification because of their incompatibility; their dispersion is not good without surface modification. Practical implications The modified silica surface is considered as effective reinforcing filler which can replace other fillers because of its lower surface energy and enhanced intercalating behavior in rubber. Social implications This study is just a start in establishing rubber projects with wide applications in the industry and providing a cheap local product while preserving the quality and that is the use of factory waste, which helps in protecting the environment from pollution. Originality/value mSF is cheap with relatively high purity, which make rubber/mSF composites appear as new grade of material that can be used in different media rather than rubber.