Measurement of Thermal Conductivity of Nonwovens Using a Dynamic Method

A nonsteady-state cooling method has been used to measure the thermal diffusivity (α) of nonwovens. The method is relatively simple and requires a minimum of spe cialized equipment. The calculations required to obtain α from cooling curves are somewhat involved but can be easily performed on a small computer. The apparatus allows α to be measured at various degrees of sample compression. Thermal conduc tivity can be obtained from α if heat capacity and bulk density are known. The tech nique was used to study the effect of fiber structural parameters on the conductivity of nonwovens. The results indicate that in agreement with established theory, con ductivity decreases if the nonwoven is compressed or is made with finer fabrics or has a reflective coating on the fiber surface. This occurs because of a reduction in the radiative component of heat transfer. Fiber shape has no effect on thermal conductivity. Nonwovens made with experimental hollow fibers have lower thermal conductivity than nonwovens containing solid fibers of the same size; no explanation is currently available for this phenomenon.