Author: Sarkar, Manas Kumar
Title: Plant structured textile materials
Degree: Ph.D.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations
Textile fabrics -- Testing
Department: Institute of Textiles and Clothing
Pages: xviii, 190 leaves : ill. ; 30 cm.
Abstract: The present research comprises of two closely related parts: the development of a new absorption tester namely Transplanar Water Transport Tester (TWTT) and development of a plant-structured fabric for liquid water transport properties. The TWTT is unique in that it can not only measure the initial water absorption of the fabric in transplanar direction, but also the rate of evaporation from the fabric surface after fully saturated with water, with the temperature of water controlled at different levels simulating the end use conditions of the fabric. Compared with existing instruments for water transport behavior of fabrics or papers, the new instrument has a unique mechanism to control the water level underneath the fabric sample at a constant level (i.e. the water level is not reduced with the water transport into or through the fabric sample), as a result the measurements are not affected by the changes in hydrostatic water pressure during testing. Repeated tests on various fabric samples showed that the measurements from the instrument are accurate, sensitive and reproducible. Using this instrument it is possible to measure precisely the absorption behavior of the various textile fabrics with realistic simulation of profuse sweating condition. A biomimetic and bio-inspired approach to materials is identified as one of the most promising scientific and technological means of the coming years. In this research, some novel weave structures were developed, which emulate the branching structure of the plants responsible for high water transportation from ground to the atmosphere, enhancing the absorption and water transport property in the textile fabric. Initially, fifteen three-layered self-stitched (the different layers of the fabric are stitched together by the short movement of yarn from one layer to another layer) fabric structure, mimicking the plant structure network was postulated. In such fabrics, by grouping four (using 4/4 matt or Mockleno design) yarns in bottom layer, two (using 2/2 matt design) yarns in middle layer and a single (using Plain weave) yarn in the top layer, to some extent, the branching network was imitated as well as the increase of the ratio of surface area to volume from the bottom to the top as exists in a plant was achieved. In addition, a bunch of long pile yarns was inserted on the fabric surface to imitate the leaf of a tree. All fabrics were tested on the novel Transplanar Water Transport Tester (TWTT), to understand the absorption behavior in profuse sweating condition. The results suggest that three-layer self-stitched plant structure has better water absorption property as compared to the three-layer plain fabric. Additionally, the results reveal that long piles attached to the fabric surface can improve the surface evaporation of the fabric after completely saturated with water.
To imitate more closely the plant structure, the design was modified to incorporate the interchanging of yarns. This interchanging pattern better emulates the branching structure as the same yarns go from the bottom layer (four yarns together simulating the stems), to the middle layer (two yarns together simulating a branch) and then to the top layer (all yarns are separated in plain weave). In order to evaluate the effectiveness of the new weave design, totally twenty-four fabrics in different weave structures and interchanging patterns were produced. All these fabrics consists of polyester warp yarns, but have varying weft yarns made of Cotton, Thermolite, Coolmax fibers, respectively. All fabrics were tested with Moisture Management Tester (MMT) for measuring the one-way transport properties, and by the Transplanar Water Transport Tester (TWTT) for measuring the absorption behavior of the fabrics under profuse sweating condition. Results reflected that the plant structure fabrics have faster initial absorption property and have significant advantages in moisture management. Such fabrics can wick water faster from inner layer (touching the human body) to the outer layer, where it spreads faster and dries-up quickly. To reduce the thickness and weight of the fabric and make it suitable for the summer wear, the design was modified further. The warp-rib design was used in the back layer and the middle layer to bring the weft yarn directly from the back layer to the middle layer and then to the top-layer after interlacing with one warp at each layer and maintaining the branching structure. In addition, a two-layer plant structure was developed, where yarns from back layer (two-yarn together using 2/2 Matt design) open up in the top layer (plain weave), so as to further reduce their thickness and weight. For all plant structured fabrics better moisture management property and faster initial absorption rate were observed. Surface and cross-section of the plant structured fabric was observed under the microscope, to understand its superior liquid transport property. It is believed that faster absorption property of this fabric is a result of combination of different mechanisms. The magnified view of the fabric showed larger holes at the back side of the fabric and smaller and more number of holes at the face side of it. The step by step reduction of size of holes from the bottom to middle, then to the top layer creates a pull of capillary pressure towards the top layer. Inter-yarn channel of grouped yarns in the back layer also assist in wicking of the fabric. In addition the branching structure of yarns reduces the resistance of water flow, as suggested by earlier researchers, to enhance the water transportation.
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