Effect of silica fume and rice husk silica in bio-epoxy composites

Abstract

The plastic industry is having a rising interest in using bio-resin materials and waste materials for high performance applications. This research assesses the effect of two types of silica in the thermo-mechanical properties and curing behavior of bio-based epoxy composites. Bio-silica (B.S.), obtained from rice husk in our laboratories, and silica fume (S.F.), Aerosil 150, have been used for the development of these composites. An aliphatic epoxy resin, based on Sorbitol Glycidyl Ether (GE60), was crosslinked with two polyetheramine hardeners having oxypolyethylene (PEO) and oxypropylene (PPO) repeating units in the backbone, respectively. The bio-based aliphatic epoxy composites were prepared by a solventless procedure and were cured at room temperature. In general, the epoxy amine systems were reinforced with 3 wt% of both silicas (B.S. and S.F.). The degree of silica dispersion, thermo-mechanical properties and curing monitoring of the composites were analyzed by several techniques described in the paper. The thermal stability increased in both filled networks, but a remarkable improvement in the GE60/PEO/3BS system was observed when compared to S.F. composites. Besides, mechanical properties were also enhanced in the SGE/PEO/3BS system, with 25% of improvement in the Young Modulus and Tensile Strength respect to the other systems. However, the S.F. composites showed a more significant percentage of epoxy conversion when compared with epoxy-biosilica networks. The higher hydrophilicity of PEO was relevant in terms of B.S. dispersion, kinetic reactions, and thermo-mechanical performance.