Functional Gradient Ultrahigh Molecular Weight Polyethylene for Impact-Resistant Armor

Biomimetic functionally graded materials show excellent mechanical strength and impact resistance. Inspired by the nacre that the facing hard cell to blunt the impact while the inner backing tissues deforms and absorbs the impact energy, here we report a strategy for preparing nacre-inspired ultrahigh molecular weight polyethylene (UHMWPE) graded materials that exhibit superior energy absorption (5.7 N.m) and impact resistance (1249.7 Pa) compared to appropriate carbon steel and UHMWPE reference samples. The unique properties of our UHMWPE graded materials apparently arise from crystallinity gradients formed by transient thermal gradients during UHMWPE processing. Moreover, we demonstrate that UHMWPE graded materials can be further enhanced with appropriate inorganic nanoparticle fillers (e.g., silica nanoparticles). The thermal and mechanical properties of UHMWPE graded materials could be exploited for impact-resistant human-protection applications.