Thermal Transmittance and Air Permeability of Plain Weave Fabrics

The findings of earlier research on the influence of particular yarn and fabric structural variables on heat transfer and air flow through fabrics are used in explaining similarities and differences among measurements of air permeability and thermal transmittance of three medium-weight plain weave fabrics. Two fabrics constructed of staple polyester (PET) yarns exhibited higher air permeabilities and lower thermal transmittance values than the third fabric, which was composed of PET filament yarns. Bulk densities of the two staple yarn fabrics were approximately equal, but the fabrics differed in weight, thickness, fabric count, yarn tex, and yarn twist. The staple yarn fabric with the lowest fabric count, highest weight, and highest thickness exhibited the lowest thermal transmittance in both single and multiple layers; however, differences between its thermal transmittance values and those of the thinner, lighter weight staple yarn fabric were not statistically significant. There were significant differences in air permeability between each of the three fabrics. Measurements also were taken on multiple layers of the fabrics. Regression analysis revealed nonlinear declines in thermal transmittance and air permeability as fabric layers were increased. Differences in air permeability and thermal transmittance among the fabrics are explained on the basis of structural differences.