Thermal Effusivity Determination of Wet Textiles

C-Therm developed the modified transient plane source (MTPS) technique for measuring materials’ thermal effusivity (cool touch/warm feel). This equipment was adopted as a standard for measuring the effusivity of dry textiles and published in 2016 as ASTM D7984.

However, determining the thermal touch behavior of fabrics when wet is also crucial for the garment industry, as fabrics frequently come into contact with sweat, rainwater, and other liquids. There is no generally recognized procedure for applying the MTPS test method in characterizing the thermal touch behavior of fabrics in the wet state. This research introduces a novel approach to assess the thermal touch behavior of sportswear fabrics based on the wet thermal effusivity (WTE) at different water saturation levels.

Two separate wetting protocols were developed to create fabric specimens at various saturation levels. The WTE measurements were conducted using the air-hoop method under an applied pressure of 1 kPa between the fabric specimen and C-Therm’s MTPS (Modified Transient Plane Source) sensor.

It was observed that the WTE of sportswear fabrics increased with their saturation level. The increase in WTE was significantly higher between 75% and 100% saturation compared to the increase observed between 0% and 75% saturation. This higher increase above 75% saturation was likely due to the formation of a thin water layer on the fabric surface at saturation levels above 75%. Additionally, the study found a positive linear correlation between the WTE of fabrics at or below 75% saturation and their thermal effusivity in the dry state. On the other hand, the WTE at 100% saturation exhibited a non-linear positive relationship with the amount of water in the fabric.