Photochemical aging of an e-PTFE/NOMEX® membrane used in firefighter protective clothing

The moisture barrier membrane is an important protective layer of fire protective clothing. This membrane usually consists of a coating of expanded polytetrafluorethylene (e-PTFE) laminated to a Nomex® fabric. In this study, the effects of accelerated photochemical aging on morphology, structure and performance of ePTFE/Nomex® membrane were investigated. The mechanical properties and chemical structural changes during the photochemical aging process were studied by using appropriate techniques including infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM) and permeability measurements. The results showed a significant reduction of mechanical properties of the membrane after photochemical aging due to the degradation of the Nomex® fibers. The dramatic decrease of vapor permeability after photochemical aging was involved the closing of transpiration pores on the aged membrane surface. These results provide useful information to better understand phenomena occurring during photochemical aging of high-performance microporous laminates and may help to improve the manufacturing process for fire protective clothing.