Recent Advances and Environmental Challenges in Polymer Nanocomposites: Nanofillers, Processing Technologies, and Applications.

Polymer nanocomposites have attracted considerable attention owing to their ability to achieve substantial improvements in mechanical, thermal, electrical, barrier, and multifunctional properties through the incorporation of low concentrations of nanoscale fillers. This review provides a comprehensive analysis of recent advances in polymer nanocomposites, focusing on the relationships between nanofiller characteristics, processing strategies, interfacial interactions, and the resulting material performance. Different classes of nanofillers, including carbon-based, ceramic, metallic, polymeric, and hybrid nanostructures, are systematically compared with respect to their morphology, surface chemistry, of processing routes, including melt blending, solution processing, in situ polymerization, and surface functionalization, on nanoparticle dispersion and polymer-nanofiller interfacial adhesion is critically discussed. The review further evaluates how these factors govern the mechanical, thermal, electrical, dielectric, and barrier properties of polymer nanocomposites and summarizes their applications in aerospace, automotive engineering, electronics, biomedical devices, energy systems, construction, and advanced packaging. Current technological challenges, including nanoparticle aggregation, long-term stability, process scalability, environmental impact, and nanomaterial safety, are also examined. Finally, emerging research directions, including hybrid nanofillers, sustainable polymer systems, digital materials design, and machine-learning-assisted optimization of polymer nanocomposites, are highlighted. This review provides an integrated perspective on the design and processing of high-performance polymer nanocomposites and identifies key opportunities for future research and industrial implementation.