Preparation of hygroscopic fabric with a uniform and slow exothermic effect and its thermoregulation evaluation

Hygroscopic-exothermic textiles dissipate heat by absorbing moisture around the skin, which makes humans feel warm in a cold environment. However, the local rapid temperature rising and heat concentration due to uneven sweat distribution can cause a heat sensation that is unfavorable to personal thermal comfort in a relatively short period of time. Herein, hygroscopic fabric with a uniform and slow exothermic effect was prepared to achieve thermal-wet comfort of garments. The hierarchical structure textile consists of an inner layer with moisture diffusion and transport performance, a middle layer with moisture absorption and storage properties and an outer layer with moisture absorption and heat generation characteristics, which achieved the effect of slow and uniform heat dissipation during the moisture absorption by controlling the moisture transmission within the fabric. Based on the study of the uniform and slow exothermic effect of fabrics, five indexes, namely the average temperature value, the maximum temperature value, the temperature distribution uniformity index, the percentage of the heating area distribution at the maximum temperature point on the fabric surface and the initial heating rate, were proposed to evaluate the uniformity and the slowness of moisture absorption and heat dissipation in textiles. The result showed that the initial heating rate of multi-layer fabric could be reduced by 0.11-0.25 degrees C/min compared to the single-layer hygroscopic-exothermic fabric and there was an up to 29.93% increase in the heat dissipation area at the maximum temperature point. The uniformity of temperature distribution after moisture absorption of fabrics increased by 41.6-58%.