Mechanical and thermal behaviours of graphite flake-reinforced acrylonitrile–butadiene–styrene composites and their correlation with entanglement density, adhesion, reinforcement and C factor

Abstract

Polymer composites are prepared by melt compounding of acrylonitrile–butadiene–styrene (ABS) and graphite flakes (GFs). The fabrication of ABS/GF composites involves two steps: melt compounding of the ABS matrix and GFs in a vertical twin screw micro-compounder for a period of 3 minutes, and then sample preparation using a micro-injection moulding machine. The GF content is varied from 0 to 40 vol% with respect to the ABS matrix. The composites are characterized through tensile, flexural, impact, hardness and thermal conductivity. The thermo-mechanical behaviour is analysed by dynamic mechanical thermal analysis (DMTA). The ABS/GF composites are found to have a gradual variation in the flexural modulus, with about 6, 25 and 92% increments in the flexural modulus on addition of 1, 9 and 40 vol% of GFs in the polymer matrix, respectively. But this addition of GFs exhibits a small decrement in the tensile strength and elongation at break. The impact strength is also sharply decreased (40% reduction with only 1% GF) with the increasing GF content in the ABS matrix. The DMTA results show an improvement in the storage modulus of ∼ 250% at room temperature, and the loss modulus also increases while the damping factor decreases as the GF content increases in the composite. The degree of entanglement increases whereas the reinforcement efficiency and C factor decrease for higher GF content. These are calculated from the data obtained by DMTA. The thermal conductivity of the composites shows an increasing behaviour with an increasing amount of GFs, as a ∼250% increment is observed at the 40 vol% loading of GFs. The addition of GFs also increases the melt viscosity, and the same trend is shown by the complex viscosity. Thermogravimetric analysis shows an improvement in the thermal decomposition temperature, and the char yield shows a 35% improvement at 40 vol% loading of GFs. Therefore the GF-reinforced ABS composite with improved thermal conductivity, heat stability, viscoelastic behaviour and flexural modulus can be a promising as well as a suitable composite material for making various electronic and electrical accessories including bipolar plates for fuel cell applications.