There are factors other than safety that determine the effectiveness and wearability of protective apparel, namely comfort and appearance.
Moisture management has an impact on the wearer’s comfort and can be measured objectively. A criterion for moisture management is the evaporation of moisture or perspiration from the skin through the fabric structure. The Sweating Guarded Hotplate Test method (ISO 11092) measures the resistance of a material to let water vapour through which is expressed as Ret (water vapour resistance in m².Pa/W). A fabric’s moisture management performance is also influenced by its air permeability, i.e., the capacity to let air pass through (tested according to ISO 9237). Air permeability (expressed in litre/m²/sec.) is an important measure of comfort, because it influences the air moving through a fabric and around the skin, leaving a dry feeling on the wearer skin.
Typical single-layer fabrics made of Nomex® fibres can have better moisture management properties than cotton or cotton-blended fabrics which were treated with flame-retardant chemicals. The unique dog-bone fibre shape allows for good moisture transport along the fibre by capillarity.
Typical single-layer fabrics made of Nomex® fibres maintain their high air permeability, even after 200 washes. Cotton-based fabrics considerably loose much of their air permeability after 50 washes, most likely due to fabric shrinkage, as fabrics get denser through washing.
The values for sweat wicking time and sweat propagation after 1 minute contribute to the evaluation of the moisture management of fabrics to be used in Personal Protective Equipment.
Sweat wicking time shows how long a drop will take to dissipate throughout a fabric. Sweat propagation after 1 minute shows the surface on which a liquid will propagate after 1 minute.
Fabric construction, weave types or finishing treatments can positively or negatively influence the air permeability and the moisture management capacity of a fabric. This is why DuPont only works with a network of Nomex® Partners in Europe who offer proven quality.