Experimental Investigation of the Influence of Structural Parameters on the Radiative Transmittance of Goose-Down Polyester Nonwovens for Cold Weather Clothing

The lower effective thermal conductivity of goose down fibres provides an excellent thermal insulator property, which is mainly assumed due to its air-entrapping ability and thus lower diffusive thermal conductivity. Although the effective thermal conductivity of a porous medium is a combination of both diffuse and radiative thermal conductivity, using an alternate approach, the present work attempted to quantify the influence of structural parameters on radiative transmittance, which is directly related to radiative conductivity that affect the overall effective thermal conductivity. A Box–Behnken design was used to study the effect of areal density, thickness of nonwovens, and blend proportion of the goose down fibres in non-wovens on the radiative transmittance. It was found that radiative transmittance does not decrease linearly with an increase in areal density. Also, the model predicted an interaction factor among the thickness of the nonwoven and the blend proportion of the goose down fibers; with an increase in thickness, radiative transmittance showed a decreasing trend; with an increase in goose down blend proportion, radiative transmittance decreased, but the extent of reduction was different for different levels of thickness. So, it was found that the multidirectional orientation of goose down fibres along with their fine barbules are the major factors that contributed to their lower radiative transmittance properties.