Investigation on Thermal Properties of Double-Layered Weft Knitted Fabrics

It is known, that fibre type, yarn properties, fabric structure, finishing treatments and clothing conditions are the main factors affecting thermo-physiological comfort. The warmth of a fabric is due to insulation provided by air trapped between fibres and yarns. Fabrics from straight filament yarns remove heat rapidly by conduction when placed next to the skin and in such a way produce a so-called cool feel or handle. The objects of investigation were double-layered weft fabrics knitted from cotton or man-made bamboo yarns and synthetic PA (polyamide), PP (polypropylene), PES (polyester) threads combination in three different knitting patterns. 16 samples variations were used. Thermal conductivity and thermal resistance were determined. It was established that thermal properties of double-layered knitted fabrics depend on raw material, structural parameters and knitting pattern of the fabric. Thermal resistance increases when thickness of the fabric increases, and thermal conductivity coefficient increases when loop length of the fabric increases. The highest influence on thermal properties has the kind of knitting pattern.