Microscopical Observations of the Abrasive and Ultraviolet Deterioration of Nomex® Aramid Fiber

Abstract

Nomex® trousers which had been worn by Army helicopter personnel were compared in the scanning electron microscope (SEM) to material which was ultraviolet-(uv-) irradiated and/or Accelerotor-abraded. Samples which were both uv-irradiated and abraded had greater strength loss and more fiber surface damage. Wear initiated through peeling, either on the fiber surface or along cracks that formed in the depressed center of the “dogbone” shaped fiber. Short fibrillation eventually caused fiber severing. The Accelerotor reproduced the individual fiber damage observed in field-worn Nomex, but distribution of wear within damaged yarns was different. SEM examination revealed thatuv radiation aggravated the decomposition and gas formation in Nomex fiber ends which had been exposed to a singeing flame, resulting in burst bubbles with rough surfaces and jagged edges. This condition is thought to be associated with reported tactile discomfort with original production lots which had been singed. Fiber-fracture patterns from fabric tensile tests were quite variable, and no distinct trends were observed.