PE here refers to UHMW-PE, the abbreviation of ultra-high molecular weight polyethylene. It is a high-performance organic fiber developed in the early 80S of last century. It has great ultra-high stability, low temperature resistance, and water resistance, which makes the maintenance of PE bullet-proof products more convenient; but it also has some a few drawbacks. For example, it is vulnerable to high temperature, and doesn't resist creep as well as Kevlar. Due to its poor creep resistance, it cannot be used under high pressure for a long time. But compared with Kevlar helmet, it is lighter in weight and much cheaper.