Field and Laboratory Aging Effects on Poly(p-phenylene benzobisoxazole) Fibers Used in Body Armor

Abstract

In recent years, poly (p-phenylene benzobisoxazole) (PBO) fibers have become prominent in high strength applications such as body armor, ropes and cables. This study compared the mechanical and chemical properties of yarns extracted from PBO body armor exposed to elevated temperature and moisture in the laboratory with yarns from body armor that had failed in the field. During 26 weeks of laboratory aging, a 30 % decrease in yarn tensile strength was observed, which could be correlated to the disappearance of key PBO functional groups as measured via infrared spectroscopy. In field armor, a similar decrease in tensile strength was observed, but the changes in chemistry differed from those observed in the laboratory aging study. Differences in chemical degradation and mechanical damage mechanisms between the two sets of armor are discussed.