Water Transport Mechanisms in Textile Materials1 Part I: The Role of Yarn Roughness in Capillary-Type Penetration

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Abstract
The movement of liquid water in fiber assemblies such as yarns and fabrics is examined in terms of a theory of water transport based on a capillary penetration mechanism. Yarn construction features, such as twist, diameter, crimp, and fiber denier, are shown to be related to the rate of water transport in such fiber assemblies. From measure ments of yarn and fiber water contact angles, it is shown that water transport in yarns is only slightly influenced by the wetting properties of the individual fiber materials and depends mainly on the wetting behavior of the whole yarn. Increase in yarn roughness due to random arrangement of its fibers gives rise to a decrease in the rate of water transport, and this is seen to depend on two factors directly related to water transfer by a capillary process. (1) The effective advancing contact angle of water on the yarn is increased as yarn roughness is increased. (2) The continuity of capillaries formed by the fibers of the yarn is seen to decrease as fiber arrangement becomes more random. The measurement of water transport rates in yarns is thus seen to be a sensitive measure of the properties of fiber arrangement and yarn roughness in textile assemblies. The present studies on cotton, nylon, Dacron, wool, and wool blended yarns thus indicate that an appropriate choice in fiber crimp, fiber denier, yarn size, and blend uniformity are all important in obtaining blended fabrics of desired properties.