C-Therm Blog

Application of Thermal Effusivity: Performance and Comfort of Disposable Diapers

Nothing feels better on a baby’s skin than a dry, warm diaper! Diapers are made of 3 key layers: the topsheet, the surge layer, and the absorbent core. When wetted, the diaper’s surge layer disperses the liquid throughout the absorbent core, reducing the wetness from the topsheet and the overall coldness of the diaper.

Thermal effusivity can quantify the diaper’s ability to exchange thermal energy between the diaper and the baby’s skin. In characterizing the thermal effusivity of the diaper under dry and wetted conditions, the performance of the diaper can be quantified as to a critical performance attribute for the product based on touch or feel. High effusivity values represent a “cool-feel” and low effusivity values indicate a “warm-feel” to the material. Water has an effusivity value of ~ 1600 W s1/2 m-2 K-1, compared to a dry diaper in the range of 50-100 W s1/2 m-2 K-1

The chart below highlights a study of two diaper brands. The thermal effusivity of two diaper specimens were measured by the C-Therm TCi Thermal Analyzer. Employing the Modified Transient Plane Source (MTPS) technique, the TCi Thermal Analyzer conforms to the ASTM D7984 standard. Results from testing the specimens under dry condition, subsequent wetting, and after being wetted for 12 hours are compared respectively.

To learn more about thermal effusivity and how to quantify the warm feel or cool touch of textiles and fabrics, please go to


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