Nanocomposite Polymer Gears: A Review

Polymer gears are increasingly used as lightweight, low‐noise alternatives to metal gears, but limited strength, thermal stability, and wear resistance restrict their use in demanding applications. This review examines recent advances in nanocomposite gears based on engineering thermoplastics, including polyoxymethylene, polyamides, polybutylene terephthalate, high‐density polyethylene, acrylonitrile–butadiene–styrene, and polyaryletherketones. This review provides a nanofiller‐centered synthesis and distinguishes material‐level property data from gear‐level evidence on wear, failure, and service life. Nanofillers are classified by morphology as zero‐dimensional particles, including carbon black and nano‐CaCO 3 , one‐dimensional carbon nanotubes, two‐dimensional graphene and nanoclays, and hybrid filler systems are also discussed. Their effects on crystallization, interfacial bonding, stress transfer, thermal dissipation, and tribological behavior are discussed, with particular emphasis on filler loading and dispersion. Reported optimal loadings of approximately 0.02–6 wt% increase strength by 10%–63% and modulus by 15%–113%, reduce wear rates by up to 61%, and more than double gear service life. Nanofillers can also shift failure toward milder abrasive wear, crack deflection, and localized plastic deformation. Manufacturing routes, current limitations, and future research priorities are identified.