Since despite the best efforts of manufacturers, some vulnerability of body armor materials to aging due to hydrolytic or oxidative environments is expected and may result in the degradation of material properties such as tensile strength, the current study exposed p-aramid yarns from two body-armor manufacturers to environmental conditions of various fixed temperature and humidity combinations.
The maximum temperature and humidity conditions were 70℃ and 76 percent relative humidity (RH). Tensile tests were performed on specimens extracted at several different times over the course of at least 1 year to determine the change in ultimate tensile strength and failure strain as a function of time, temperature, and humidity. Molecular spectroscopy was used to investigate any chemical changes as a result of the aging. The p-aramid materials were found to be generally resistant to degradation at most conditions, showing changes of less than 10 percent only at the highest temperature and humidity conditions. (publisher abstract modified)