The effect of graphite on the properties of natural fibre hybrid bio-composite for automotive applications

Abstract

A vast amount of waste is produced from the agricultural-based industries, and most of this waste is regarded as unwanted materials. Because the majority of the agrowaste is underutilized, this kind of waste is disposed by dumping in landfill and/or burned. Burning of this waste has serious consequences, such as contributing to greenhouse gas emissions. There is a need to utilize this waste in a positive way in order not to harm the environment. This study reports on the conversion of maize stalks through various physical and chemical methods into a maize stalk fibre (MSF) material that can be used as a reinforcing filler in a biopolymer matrix. Maize stalk with a content of 10 wt% was incorporated into the polybutylene succinate (PBS) matrix for advanced applications. However, both the maize stalk and PBS are known to be flammable; as a result, flame-retardant fillers such as expandable graphite (EG) and montmorillonite (MMT) clay are incorporated into the system at 3 wt% to form hybrid composites. The effect of expandable graphite and its synergy on the morphology, flammability properties, thermal stability, dynamic mechanical analysis, and rheological properties of the PBS/maize stalk fibre are reported in this study. According to the SEM images, PBS/MSF composite shows poor interaction between the fibre and PBS matrix, with clearly observable fibre pull-outs in the system. However, the incorporation of modified MMT improves the interaction between the fibre and PBS matrix, which also has a positive impact in various properties. Even though there seems to be minor interaction between MMT and EG in the PBS/MSF composite according to SEM, because of their rigidity, the fillers still improve the properties of the hybrid composites. The PBS/MSF/MMT shows better flame-resistant properties than PBS/MSF/EG composites; however, the synergy of the two fillers showed better flame-resistant properties than both PBS/MSF/MMT and PBS/MSF/EG composites. The synergy of filler seems to interact better with volatile products of degradation, as the PBS/MSF/MMT/EG reveals higher thermal stability when compared to 90/10 PBS/MSF, PBS/MSF/MMT and PBS/MSF/EG. Because of a slightly better interaction of the components in PBS/MSF/MMT, this particular system shows higher storage modulus when compared to a PBS/MSF/EG composite. The presence fillers reduced the degree of crystallisation of the composites and its hybrid biocomposites when compared to the neat PBS.