Mechanical and thermal synergy in natural fibre thermoplastic composites: A review for automotive, construction and packaging applications

Natural fibre-reinforced thermoplastic composites have emerged as sustainable alternatives to conventional synthetic fibre-reinforced composites owing to their low density, renewability, recyclability, and favourable mechanical properties. This review critically examines recent advances in natural fibre-reinforced thermoplastic composites, with particular emphasis on their mechanical performance, thermal stability, and suitability for applications in the automotive, construction, and food packaging sectors. A comprehensive analysis of published literature is presented to establish the relationship between composite composition, processing techniques, and functional performance. Mechanical and thermal characterization is highlighted as a key criterion for selecting appropriate natural fibre–thermoplastic combinations for specific engineering applications. Despite their significant advantages, the widespread adoption of natural fibre-reinforced thermoplastic composites is constrained by poor interfacial adhesion between hydrophilic natural fibres and hydrophobic thermoplastic matrices. The review discusses various surface modification techniques and the incorporation of coupling agents to enhance fibre–matrix compatibility, thereby improving the mechanical strength, thermal stability, and durability of the composites. The influence of processing methods, particularly extrusion compounding followed by injection moulding, on the overall performance of natural fibre-reinforced thermoplastic composites is also examined. The application-specific performance requirements of these composites are critically evaluated. In the construction sector, emphasis is placed on load-bearing capacity, moisture resistance, and long-term durability for components such as doors, roofing panels, and interior building elements. For automotive applications, the review discusses the importance of achieving an optimal balance between lightweight design, mechanical integrity, and thermal resistance to improve fuel efficiency and withstand elevated service temperatures. In food packaging, the sustainability, biodegradability, and barrier properties of natural fibre-reinforced thermoplastic composites are assessed as environmentally friendly alternatives to conventional petroleum-based plastics. This review demonstrates the transition of natural fibre-reinforced thermoplastic composites from environmentally sustainable materials to high-performance engineering composites tailored for targeted commercial applications. In addition to construction, automotive, and packaging, their expanding potential in consumer products and biomedical applications is also discussed, highlighting future research directions for improving multifunctional performance and large-scale industrial adoption.