Effect of Arthropod Repellents on the Mechanical Properties of Common Materials Used by U.S. Service Members

Arthropod-borne infectious diseases represent a serious threat to U.S. military personnel, and insect repellents are commonly used as the first line of defense against those illnesses. Recent feedback from the field suggests that currently provided repellents, which are based on N, N-diethyl-meta-toluamide (DEET), damage or alter some of the military-relevant materials. The aim of the current study was to evaluate the effect of DEET and non-DEET repellents on the mechanical properties and appearance of commonly available synthetic materials (substrates) routinely used in military application. We measured the visual appearance, visible light transmittance, strength, and stiffness of four materials exposed or left unexposed to six repellents. Sheet materials were tested in four-point bending, and the thread material was tested in uniaxial tension. Some of the repellents significantly altered the strength and bending stiffness of the sheet material and reduced light transmission. The sheet materials tested are commonly used in lens applications, so the reduction in light transmission and visibility has practical implications. For the thread (Kevlar) material tested, two repellents significantly reduced thread strength. Kevlar is used in the manufacture of body armor, but it is unknown if a reduction in Kevlar strength reduces the protective value of the body armor.