Ultra-high-molecular-weight polyethylene (UHMWPE) fiber is widely used for flexible ballistic products due to it high specific strength and modulus. However, with the emergence of advanced ammunition and firearms, materials with enhanced mechanical properties are always in great demand. This research aims to develop environmentally friendly approaches for fabricating nanocomposite coated UHMWPE filament yarns/fabrics. Waterborne polyurethanes (WPU) and inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles were used. Graphene nanoplatelets (GNPs) were later added for comparison. A study conducted to understand the effects of dispersion medium and coating composition on PU/IF-WS2/UHMWPE yarns, shows water and water/ethanol mixture are suitable for preparing the nanofluids and uniform coating. Improved mechanical properties and additional matrix-related failure mechanisms are observed for coated samples. Continuous yarn coating contributes to higher efficiency and better yarn alignment than individual coating. Additionally, thermoset PU leads to higher sample wash durability than thermoplastic PU. Also, plasma pretreatment (PT) induces functional groups (-OH, C=O, C-O) on the fiber surface and improves sample performance and durability.
Part of this study focused on the PT and PU/IF-WS2 coating on woven fabrics. The PT lowers fabric water contact angle from 105.2° to 81.1° and greatly strengthens coated fabrics, with up to 73%, 137%, 694%, and 757% higher toughness, elongation, storage modulus, and loss modulus over neat fabrics, respectively. Up to 98.8% of the coating is retained after washing. Increasing PU amount and curing temperature improves wash durability but decreases toughness. IF-WS2 and stabilizer amounts show significant effects on yarn toughness. The optimal conditions are 1% solid IF-WS2, 10% PU, 5% stabilizer, and 120℃ for curing.
Then, PU/nanofiller films were prepared with varying amounts of IF-WS2 or GNPs to study the mechanisms. Adding water-based IF-WS2 enhances film performance due to its reinforcing effect and uniform distribution, whereas GNPs decrease film properties due to their negative impact on film formation.
Herein, a thorough study on the effects of various critical parameters on formed composites is presented. The developed materials achieved vastly improved mechanical, viscoelastic, and energy absorption performance based on the same weight, therefore are highly promising for lightweight and flexible body armor and anti-impact uses.
