Study On Heat-Moisture Comfort Of Cotton-Like Polyester Knitted Fabrics With Various Blend Ratios

Part of the technologies and products of polyester fiber industry in China has reached international advanced level. However, it’s facing outstanding problems such as less varieties, low yields, low quality of high value-added functional fiber, fierce homogenization competition and low profit margins in this field. Cotton-like concept met inner needs of transformation and upgrading in polyester industry. It also contributed greatly to textile shocks from high cotton price and the situation of China’s long time dependence on cotton import. Heat-moisture comfort of textile products directly affects physiological and psychological satisfaction, which are important elements of cotton-like. Therefore, study on comfort of cotton-like fabric was of great guiding significance to development of cotton-like fabric.A novel modification polyester fiber developed by our project team was used as raw material. Six kind of cotton-like knitted fabrics with different blending ratio were designed, their heat-moisture comfort were studied. The paper has probed into basic structural parameters and thermal-wet comfort property of these knitted fabrics at first. Effects of blending ratio and fabric structure parameters on thermal-wet comfort were discussed. Secondly, pore structure of cotton-like polyester knitted fabric such as pore size, distribution and porosity were characterized. The relationship between and pore structural parameters and the basic fabric structure parameters, heat-moisture transfer properties of fabrics were analyzed, which further provided basis for design of fabric structure and comfort. At last, we treated cotton-like fabric as hydroscopic porous fiber assembly mixed with fiber water and air. Combined with porosity and water content, mathematical prediction model of the thermal conductivity on moisture absorption porous fabric was established. VB program to forecast thermal conductivity of experimental cotton-like fabric was developed. These provided theoretical foundation for study and design of cotton-like polyester fabric comfort.The result has shown that with content of modified polyester fiber increased, thickness and weight of the fabric first increased and then decreased. General trend of1-6#fabric moisture absorption and liberation were the same. With modified polyester content increased, equilibrium moisture regain and moisture absorption and liberation rate decreased. Content of modified polyester fiber and moisture regain and had clear impact on fabric structure parameters and heat-moisture transfer properties of fabrics.The results showed that the pore diameter of blended knitted fabrics presents an asymmetric distribution, that is, the smaller pores have a greater proportion to the total pores than larger pores. There exists an obvious diameter change in the pore size distribution which indicates the transition from intra-ya pores to inter-yarn pores. Average flow aperture and macro pore percentage of1-6#fabric both first decreased and then increased. Yarn blend ratio showed a greater impact on mean large pore of fabric. Yarn diameter, unfullness coefficient had significantly correlation with percentage of large and small pores. Average flow aperture and large pore fluid affected heat and moisture transfer of fabric more. Besides large pore showed greater effect on fabric permeability and correlation coefficient between average smaller pore size and fabric wicking was0.94. Significantly correlation were found from loop model porosity to fabric unfullness coefficient, thickness and loop density. The results showed blend ratio, yarn diameter, unfullness coefficient, fabric thickness and loop density have great influence on air permeability of fabrics. Volume porosity by density method indicated more effect on heat and moisture transfer index.Mathematical model was applied to predict thermal conductivity of fabric. When fiber content of cotton-like polyester is high (1#,2#,3#fabrics), small differences was found from comparison of predicted and experimental values by density method.With polyester content decreased, differences from theoretical values and experimental values differed greatly, it may be related to inconsideration of Water evaporation in fabric. Predicted values of thermal conductivity based on porosity by density method were consistent with experimental values, that’s first increased and then decreased, which provided some academic reference to the variation rules of thermal conductivity of fabric in different blending ratio.