Breathable clothing which transports the sweat away from the skin in the form of water vapour is required to prevent heat accumulating in the body. The hydrophilic part of the membrane absorbs moisture from the body and transports it to the outside via evaporation. Water vapour molecules are transported to the outside along molecular chains.
This feature is important to prevent the wind-chill effect, i. e. the subjective feeling of cold in windy weather. A sportsperson subjected to a gust of wind of approx. 25 km/h at a temperature of +5 °C actually feels a temperature of -6 °C. The higher the wind speed, the lower the air temperature is perceived.
Those doing outdoor sports are directly exposed to the weather and should be prepared for any situation. Thus, functional material must be waterproof, which depends on the membrane, fabric structure and type of coating. The impermeability of a material is measured based on the water column under the pressure of which water starts to permeate the material. If this pressure exceeds 1,300 mm, the garment is impermeable in accordance with the German Industrial Standard (DIN EN 20811:1992, or ISO 811), garments featuring pressure values between 400 and 1,300 mm being referred to as water-repellent.
Laminate with membrane
MThe membrane and the outer fabric are combined to form a laminate. This means that the outer fabric is joined to the membrane. If lining is used, it is loosely located beneath. As a rule, laminates are used for light-weight yet extremely robust sports and leisure jackets. In this context, a membrane is a material integrated invisibly inside waterproof garments to provide reliable protection against wind and moisture. Thanks to their water vapour permeability, membranes also foster a pleasant body climate.
Seam sealing means sealing the seams on the top fabric by means of a waterproof adhesive tape. Moisture is thus prevented from permeating to the inside through the seams. The water vapour permeability of the membrane, in turn, ensures moisture transport to the outside in spite of the sealed seams.