Tailoring the Properties of Polyurethane Composites: A Comprehensive Review

Polyurethane (PU) composites have emerged as versatile materials with superior mechanical, thermal, electrical, and functional properties due to the incorporation of advanced reinforcements such as graphene, carbon nanotubes (CNTs), metal oxides, and bio-based fillers. This review provides a comparative analysis of these reinforcements, highlighting their effectiveness in enhancing PU properties for diverse industrial applications. Graphene-based additives exhibit the highest improvement in mechanical performance, with tensile strength increasing by up to 320% and modulus by 40%. Multi-walled carbon nanotubes (MWCNTs) enhance electrical conductivity by 70% and improve electromagnetic interference (EMI) shielding effectiveness by 50%, making them superior for electronic applications. In contrast, nano-clays and silica-based fillers significantly improve thermal insulation, reducing thermal conductivity by 40% while also increasing compressive strength and abrasion resistance. Metal oxide nanoparticles, such as boron nitride and molybdenum disulfide, contribute to 30% higher thermal stability, 50% improved flame retardancy, and enhanced corrosion resistance, making them ideal for protective coatings. Bio-based fillers, including cellulose nanofibrils, improve sustainability by increasing tensile strength by 15%, enhancing water resistance, and reducing environmental impact. Hybrid reinforcement strategies integrating multiple fillers demonstrate the highest versatility, achieving balanced mechanical, thermal, and electrical performance. Additionally, recent advancements in dispersion techniques have mitigated agglomeration challenges, ensuring uniform filler distribution and consistent property enhancement. Despite these advancements, scalability remains a key challenge, particularly in maintaining cost-effectiveness while integrating eco-friendly bio-based fillers. Future research should focus on optimizing recyclability and multifunctionality to develop next-generation high-performance PU composites tailored for aerospace, automotive, and biomedical applications.