Isomerizaiton Azo/Epoxy Copolymer with Nano TiO2 Hybrid Coating for Enhancements of UV Protection and Interfacial Adhesion of PBO Fiber

Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber, made from a rigid-rod isotropic crystal polymer, exhibits exceptional tensile strength, thermal stability, and creep resistance, surpassing Kevlar fiber (one of high-performance bullet proof fibers) with twice the strength and modulus. However, UV exposure cleaves the oxazole rings in PBO’s molecular structure, leading to decreased crystallinity, reduced mechanical strength, and limited suitability for outdoor applications. This study introduces a novel surface enhancement method using an olefin addition reaction with an azobenzene polyepoxy (Bt-APDB-BA-GMA) coating for Ultraviolet (UV) resistance. Further combining this with nano titanium dioxide (TiO 2 ) forms an organic-inorganic layer for additional protection. Comparative studies were conducted on three samples, including original PBO fibers (PBO), PBO fibers modified with azobenzene/epoxy copolymer (PBO/azo-epoxy), and PBO fibers modified with both azobenzene/epoxy copolymer and nano TiO 2 (PBO/TiO 2 @azo-epoxy). Modified fibers showed significant improvements: PBO/TiO 2 @azo-epoxy exhibited a 63 % higher pull-out strength (34.58 MPa) and retained 78.2 % tensile strength after 288 hours of UV aging, compared to 28.2 % for unmodified fibers. This innovation enhances PBO fiber durability, UV resistance, and interfacial bonding, paving its way for broader applications in body armor, aircraft, and advanced technologies.