Vapor permeability of membrane textile materials under near-operational conditions

The article considers requirements to vapor permeability of membrane materials for waterproof clothing. Operational conditions of waterproof clothes are analyzed; the significance of test conditions for interpretation of research results and revealing factors that have a significant influence on the ability of membrane materials to transport water vapor from the space under the clothes to the outside, while maintaining a high level of water permeability is underlined. The analysis of conditions for tests of vapor permeability of materials by standard methods is performed, it is shown that they lack the ability to simulate operational conditions. The dependence of the vapor permeability of membrane materials with different structures on the temperature and on the velocity of outdoor air was revealed. It is shown that the value of vapor permeability of porous membrane materials is influenced by the variation of pore sizes and the size of the majority of pores, i.e., the greater these two values are, the higher the level of vapor permeability of the membrane porous material is. The values of the vapor permeability coefficient of materials used by sewing enterprises of Belarus for manufacturing waterproof outerwear for autumn - spring assortment have been determined. According to the experimental data, all the samples under study have a vapor permeability above the minimum allowable standard.