A new technique to measure the vapour flow resistance of textiles

The diffusion of water vapour from the human body involves passage through a confined air layer between skin and fabric, through the textile itself, acid across an outer boundary layer, Measuring the vapour flow resistance of the textile also needs a precise determination of the two air layer resistances, which is difficult to achieve, These three resistances are first visualized on a holographic bench, and then the mass flow is obtained with high accuracy using a micro-weighing technique: the evaporation rate is measured as a function of time for configurations of one and two fabric layers which seal a calibrated drum of evaporating liquid. Using benzene instead of water gives heavier vapours and a greater and more easily measured evaporation rate. The results can be easily converted to their equivalent air thickness for water vapour, The agreement between theory and measurement leads to useful insight into the relative importance of the fabric resistance compared with that of the two adjoining air layers, The technique described here is not applicable to all types of textile, especially less porous structures.