Powertex® replicates the way in which a plant transpires and passes vapour from inside the leaf into the atmosphere. Likewise, trapped vapour molecules are efficiently removed from beneath the fabric by the flexing action of minute dome-shaped chambers, each with a tiny pore centered within the body of the material. Powertex® technology is based on the laws of thermodynamics and diffusion—that heat will always transfer from a region of high temperature to a region of low temperature and that, in an attempt to regain equilibrium, water vapour will tend to move from a region of higher density to a region of lower density.
The unique design of Powertex® vapour chambers provide the conditions to establish a steep diffusion gradient at the pore exit. The efficiency of this configuration allows maximum vapour extraction whilst minimising the loss of heat. To facilitate this process, it is essential to provide an air space (the chamber) into which the excess fluid can evaporate and collect as vapour.
In optimum conditions the ratio of surface area available to collect the water vapour (at skin surface) to the area of the exit pore must be determined so as to allow the existence of constant back pressure within the system. If this is not observed, excessive convection will result in uncontrolled loss of heat.
This process is aided by the users movements in two ways. Firstly, as air movement across the pore aperture increases (outer surface), the removal of vapour-laden air and its replacement by relatively dry air results in an increased rate of diffusion. Secondly, the natural movement and flexing of the fabric, particularly in the dome region, assists the removal of water vapour by a ‘pumping’ action. This action increases with higher levels of physical activity, enabling the fabric to regulate its performance to match the production of perspiration by the user.