Nanoparticle-Infused UHMWPE Layer as Multifunctional Coating for High-Performance PPTA Single Fibers.

High-performance fibers made of poly-(p-phenylene terephthalamide) (PPTA) with high stiffness and high strength are widely used in body armor for protection due to their high degree of molecular chain alignment along the fiber direction. However, their poor mechanical properties in the transverse direction and low surface friction are undesirable for applications requiring resistance to ballistic impact. Here we provide a simple yet effective surface engineering strategy to improve both the transverse mechanical properties and the tribological property by coating PPTA fibers with ultra-high molecular weight polyethylene (UHMWPE) embedded with silica nanoparticles. The coated-PPTA fiber shows remarkable enhancement in transverse mechanical properties including ~127% increase of Young's modulus, which is attributed to both the alignment of UHMWPE chains in the transverse direction and the embeded ceramic nanoparticles. Meanwhile, the surface friction of the coated fiber increases twofold as a result of the ceramic nanoparticles. In addition, the coated fibers exhibit an enhanced chemical resistance to external harsh environment. The improved transverse mechanical properties, surface frictional characteristics, and chemical resistance demonstrate that coating with UHMWPE and ceramic nanoparticles can be used as an effective approach to enhance the performance of PPTA and other high-performance polymer fibers for body armor applications.