Evaluation of mechanical, thermal, and flammability properties in biochar-infused polymer composites from bael fruit and cashew shells: a comparative study

The natural composite trend emphasizes the use of renewable resources that possess enhanced qualities, boosting environmentally friendly solutions and minimizing the carbon footprint in numerous sectors. The present investigation aims to utilize sustainable biochar elements as reinforcements in polymeric composites. Biochar materials were produced using the pyrolysis process using waste biomass from cashew and bael fruit shells. Composites were created through the use of polypropylene (PP) as the matrix and biochar materials as the reinforcement. The three distinct weight percentages of filler were used, specifically 2.5%, 5%, and 7.5 wt.%. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and proximate analysis were used to examine the surface morphology, crystalline structure, and fixed amount of carbon in the synthesised biochar materials. The flammability properties, such as the maximal heat release and smoke production, were assessed using cone colorimeter analysis. The materials containing 5% bael fruit shell biochar had a significant increase in tensile strength, exhibiting 54.66% greater strength in comparison to pure PP. The hardness and durability of composites decreased as a result of inadequate interfacial bonding when the filler content was increased from 5 to 7.5%. The inclusion of biochar resulted in a considerable reduction in both the maximum rate of heat release (MRHR) and smoke generation of the biocomposites. Specifically, the MRHR decreased from 1083 KW/m² for pure polypropylene to 584.36 KW/m² for biocomposites containing 7.5 wt.% of bael biochar. Thermogravimetric studies revealed that the addition of biochar materials greatly improved the thermal integrity of the composites. The materials containing 5 wt.% bael biochar demonstrated enhanced heat resistance, resulting in a residual mass of 8.32%. It is clear that biochar-based polymers are potential materials for diversified industrial applications, especially in the automotive industry, where the enhanced strength and thermal stability of components such as interior panels, dashboards, or under-the-hood parts are important. Biochar made from waste biomass can also help reduce waste and promote sustainability, with numerous environmental benefits.