Development of transparent polymer armour based on high-strength polyethylene films

Impact-resistant and anti-ballistic composite materials for personal protection are typically either non-transparent, such as those made from ultra-high molecular weight polyethylene and aramid fibres or transparent materials like laminated glass, which have limited formability, or plastic sheets like polycarbonate or polymethyl methacrylate, which offer relatively low mechanical strength. This paper introduces a method to enhance the impact and ballistic resistance of polycarbonate or polymethyl methacrylate laminates, commonly used in protective visors, by integrating oriented, high-strength, transparent high-density polyethylene films. These films, as strong as steel yet significantly lighter, are produced via cast-film extrusion followed by controlled drawing and stretching to create a highly oriented polymer structure. Exhibiting over 90% light transmittance and tensile strength up to 15 times greater than polycarbonate or polymethyl methacrylate, these transparent high-density polyethylene films substantially improved the performance of hybridised polymer laminates, achieving up to a 5% increase in ballistic resistance in PC-based systems and a nearly 200% improvement in polymethyl methacrylate-based systems. Impact tests revealed a 10-fold increase in absorbed energy for high-density polyethylene reinforced polymethyl methacrylate laminates, while maintaining optical transmittance above 80%. This study represents a significant impact of high-density polyethylene films as a lightweight, transparent reinforcement in enhancing existing armour and protective equipment for use in law enforcement, public safety, military, and recreational settings.