Study On The Thermal Insalation Property Of Cotton Hollow Yarn Fabric

In the 1950s-1960 s warm colors were used to bring people a warm sense, as well as increasing the fabric thickness to improve the warmth of clothing. In early stage,as raw material cotton and wool were usually made of warm and comfortable underwear. For higher thermal insulation properties,the thicker fabric was used to reduce the heat loss and air convection.However,the fabric thickness was out of all proportion to the thermal insulation properties. When increasing the fabric thickness up to a certain extent,there was no significant increase of thermal insulation properties,body activities and appearance were also affected.In order to achieve good thermal insulation properties and reduce the fabric thickness, people constantly developed a variety of warm-keeping products. Cotton hollow yarn fabric is a new type of thermal insulation material in recent years. It has good comfort,softness,bulkiness, excellent water absorption and fast drying.The thermal conductivity of static air is smaller than that of all kinds of textile materials. In textile materials,the greater the content of static air,the better the effect of thermal insulation.By changing yarn structure and increasing the amount of cavity and porosity in the yarn,the content of stationary air in the fabric can increase,so as to achieve the purpose of improving the thermal insulation effect.In this paper,the factors influencing the thermal performance of cotton hollow yarn were studied,including hollow structure,volume density and fabric structure.At the same time,the relationship between the air permeability,moisture resistance and the thermal performance of cotton hollow yarn fabric were also studied.It laid the foundation for further development and application of cotton hollow yarn fabric.The contents of this paper were:(1) the appearance of cotton hollow yarn was studied. The longitudinal section and cross section of the yarn were taken by SEM. The longitudinal section and cross section of the hollow yarn and the ordinary yarn were compared and analyzed, which reflects the characteristics of cotton hollow yarn.(2) the effect of hollow structure on thermal insulation performance of cotton hollow yarn was studied, and the difference of warmth retention ratio, clo value and thermal conductivity of cotton hollow yarn and ordinary yarn were compared and analyzed. The hollow structure of cotton hollow yarn had caused an increase of the content of still air in fabric, formed micro separation and closed state without convection, suppressed the free convection, reduced heat conduction effectively. So the thermal performance of cotton hollow yarn fabric is better than that of ordinary cotton yarn fabrics.(3) the effect of bulk density on the thermal performance of cotton hollow yarn was studied, and the relationship between thermal performance and bulk density was analyzed. With the increase of bulk density, warmth retention ratio of the fabric was first increased and then decreased, and the thermal conductivity was first decreased and then increased. It was concluded that the hollow yarn structure can improve the thermal insulation property, but the hollowness should be moderate.(4) The effect of the weave patterns and texture on the thermal performance of cotton hollow yarn fabric was analyzed. Five knitted fabrics were selected, including weft plain, single bead cloth, 1 x 1 rib, 1+1 double rib, 1+1 double rib air layer. CLO value and thermal resistance of five fabrics were also studied and compared.(5) The effect of air permeability on thermal performance of cotton hollow yarn was studied and analyzed.The air permeability of cotton hollow yarn fabirc was first increased and then decreased along with warmth retention ratio, CLO value,thermal conductivity. For the hollow structure of cotton hollow yarn fabric,at lower air convection coefficient, the air in hollow is not affected by or rarely affected by the convection of the outside air, which ensures the good thermal insulation of the fabric; at higher air convection coefficient, the hollowness could form an air flow passage, which increased the air permeability.(6) the effect of moisture resistance on thermal properties of cotton hollow yarn fabric was analyzed. The bigger the heat insulation, the better the warmth retention, the lower the evaporative heat dissipation, the bigger the moisture resistance.This research had certain guiding significance and reference to the production and development of cotton hollow yarn in theory and practice.