Capillary flow of liquid water through yarns: a theoretical model

In extreme weather conditions and activity levels of human subjects, evaporation of sweat is critical for maintaining the sensorial and thermal comfort. Fabrics, from which clothes worn next to the skin are made, play an important role in facilitating the transfer of body liquid perspiration away from the skin to the environment through the mechanisms of capillary flow and evaporation. This work is a theoretical and experimental investigation of water flow characteristics of yarns with relevance to their structure geometry and constituent fiber chemistry. A theoretical model to predict the capillary flow of liquid water through yarns was proposed. The model is based on the Kozeny–Carman equation, which represents interfiber pores in terms of the hydraulic radius theory. Cotton, polyester and cotton/polyester yarns were produced by systematically varying different production parameters, including fiber type, yarn twist, yarn linear density and blend ratio. Plain knitted fabrics were produced and yarns taken from the produced fabrics were tested for horizontal linear flow of liquid water. The experimental results showed a strong correlation with the estimated results based on the theoretical model. The model predicts that as the ratio of interfiber pore space area to the total fiber perimeter within yarn increases, the flow rate is expected to increase.