Water vapour transfer in waterproof breathable fabrics: Part 1: under steady‐state conditions

To clarify the principles and mechanisms of water vapour transfer by diffusion in waterproof breathable fabrics for clothing, experiments using a simple glass dish were carried out under steady state conditions with and without a temperature gradient in the climatic chamber. It was found that both vapour pressure and natural convection within the air gap affect water vapour transfer. The rates of water vapour transfer are ranked microfibre fabrics, cotton ventiles, PTFE‐laminated fabrics, poromeric polyurethane laminated fabrics, hydrophilic laminated fabrics, and polyurethane‐coated fabrics. In the presence of a temperature gradient, condensation was also found to be a major factor, especially at air temperatures below 0°C. Condensation occurred the least on the inner surface of PTFE‐laminated fabrics followed by cotton ventiles, microfibre fabrics, hydrophilic‐laminated fabrics, poromeric polyurethane‐laminated fabrics, and polyurethane coated fabrics.