Improving ballistic limits of UHMWPE laminates by gamma-ray irradiation induced enhancement of interfacial bonding

Though ultra-high molecular weight polyethylene (UHMWPE) fibers are promising candidates for the design of body armor against ballistic impact, weak interfacial bonding induced by surface inertness of UHMWPE fibers would inevitably result in the fluctuation of impact resistance. Herein, we deploy a scalable Co-60 gamma-ray irradiation strategy to modify the UHMWPE fibers, which not only improves the roughness of the fiber surface, but also creates new chemical bonding between fibers and polyurethane (PU) resin. Surprisingly, the tensile strength of UHMWPE fiber is maintained very well with the introduction of small pores on surface by gamma-rays, which exhibits greater advantages than other surface modification methods. It should be attributed to the transformation of crystal structures from orthorhombic phase to more stable hexagonal phase in UHMWPE fibers. Because of the improved adhesion between fibers and PU resin, tensile strength of the UHMWPE/PU prepregs is increased by 18.5% after 10 kGy irradiation. Finally, the V50 ballistic performances of UHMWPE/PU laminates are evaluated. Most of the laminates are penetrated at the initial velocity of similar to 690 m/s except for the UHMWPE/PU laminates irradiated at 10 kGy. In addition, the delamination and back deformation of the irradiated ones are also alleviated significantly, which show great capabilities in not only preventing ballistic impact, but also reducing the injury degree of the wearer.