Comparison of ePTFE membranes with fluorine-free alternatives considering durability of laminated fabrics using hydrostatic pressure testing

Abstract

Pleasant wearing comfort is achieved using laminated fabrics containing a waterproof and breathable membrane. The most used membrane type is expanded polytetrafluoroethylene. Due to the negative impact of perfluoroalkyl and polyfluoroalkyl substances on the environment, fluorine-free alternative materials are necessary. In this work, alternative membrane materials, polyurethane and polyethylene terephthalate, were compared with expanded polytetrafluoroethylene. First, the mass per unit area, thickness, tensile properties, water vapor resistance, and hydrostatic pressure of corresponding laminates were determined. Furthermore, their durability, which is an essential aspect of sustainability, was investigated. Therefore, they were hydrolyzed, weathered, washed, and incorrectly treated (e.g. washed with fabric softener) and then investigated for hydrostatic pressure resistance, by scanning electron microscopy, infrared spectroscopy, and digital microscopy. It was shown that polyethylene terephthalate and expanded polytetrafluoroethylene are comparable with respect to breathability, waterproofness (>20 bar), and durability. However, the hydrostatic pressure resistance (approximately 11 bar) and the water vapor resistance values (>23 m² · Pa · W⁻¹) of microporous polyurethane membranes are poorer, but they still provide suitable alternatives. In addition, a beginning degradation of polyurethane could be proved after hydrolysis and weathering. Furthermore, the deposition of calcium salts on all membranes was observed after washing with tap water, fabric softener, and washing agents.