Improvement of flame retardant properties of ABS/organomonmorillonite nanocomposites with silicon compounds prepared from agricultural wastes

Abstract

This research involves an improvement of flame retardant properties of acrylonitrile-butadiene-styrene (ABS) by varying type and amount of modified silica, type of silatrane, and organomontmorillonite (OMT) loading. The silica was extracted from agricultural wastes such as rice husk and corn cob by acid hydrolysis. The obtained rice husk silica (RHS) and corb cob silica (CCS) were surface-modified with silane coupling agents, i.e., vinyltrimethoxysilane (VTMO) and 3-aminopropyltrimethoxysilane (AMMO) before blending with ABS and OMT at various ratios by melt-blending technique using twin-screw extruder. After that, RHS and CCS were used as a starting material for silatrane synthesis. The synthesized silatrane at various contents was also blended with ABS and OMT. The effect of silane coupling agents and types of silatrane on flammability and mechanical properties of ABS nanocomposites were studied. The results showed that AMMO was suitable for grafting on silica. It was shown that ABS with 5 wt% of OMT, 20 wt% of AMMO-g-CCS, and 10 wt% of CCSilatrane gave the most efficiency of flame retardant properties (i.e., lowest burning rate at 18.35 mm/min and highest LOI value at 19.6%). In addition, it could decrease the burning rate up to 70.64% and increase LOI value up to 13.29% when compared to neat ABS. TEM and XRD results revealed that ABS/OMT/modified silica/silatrane nanocomposites were consisting of both intercalated and exfoliated structure. The OMT, modified silica particles, and silatrane were found to disperse and reside in the SAN matrix. In addition, OMT and modified silica could enhance flame retardant properties of ABS matrix because of a synergistic effect between OMT and modified silica by forming silicaceous layer on surface during the combustion of ABS nanocomposites. Tensile strength and modulus of elasticity increased with increasing amount of modified silica and silatrane; whereas impact strength decreased obviously. This resulted from the rigidity and agglomeration of silica and silicon containing in silatrane. No significant difference in the tensile properties between ABS nanocomposites containing RHS and CCS; they also had comparable tensile properties to those having commercial silica.