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Title: Smart materials : functional design of thermal textiles
Authors: Tong, Jiahui
Degree: Ph.D.
Issue Date: 2018
Abstract: Recently, thermal textiles have become increasingly popular because they possess advantageous characteristics that could enable them to be widely applied in fields such as body warming, physical therapy, and drug delivery. The thermal function of thermal textiles is achieved by the embedded conductive yarns. Compared with conventional thermal devices, thermal textiles offer physical flexibility and comfort in addition to thermal functions. Temperature control is one of the most important aspects of thermal textiles. Thus this study aims to explore the thermal behavior of thermal textiles and achieve precise temperature control. Specifically, this study aims to explore the factors that are relevant to the thermal behavior, such as the electrical resistance, thermal conductivity and surrounding environment. In the first stage of the study, the electrical resistance change of thermal fabrics was investigated. The results showed that the resistance of thermal fabrics will decrease when the temperature increases. The research results attributed this property to the morphologic change of conducting yarns during heating. Accordingly, a theoretical model was proposed to simulate the heating process. In the second stage of the study, the thermal behavior of thermal fabrics of different sizes was studied. A modified and generalized model was developed to simulate the thermal behavior of thermal fabrics of different sizes. In the model, different parameters including electrical resistance, thermal conductivity, fabric size and interaction between them were studied. The research results presented deviation from simulation due to two reasons: limitation of quality control in textile industry and morphologic change of textile materials. In the third stage of the study, the influence of airflow on thermal fabrics was valuated. The results show that airflow can greatly influence the heating process and a proportional relationship was found between the thermal conductivity and airflow rate. The airflow direction has a limited influence on the heating process. A quantitative model was established to simulate and predict the thermal behavior of thermal fabrics in a windy environment. In the final stage of the study, the heat process was investigated when the thermal fabric was covered by other fabrics. The results shows that there is a linear relationship between the thermal resistance of the system and the number of cover layers. The thermal resistance brought from multiple-cover layers can be estimated by simply adding up the thermal resistance of each piece of cover layer. Furthermore, the thermal conductivity measured by a thermal conductivity meter is different from the implied thermal conductivity in the heating process. Both internal parameters and external factors that can influence the heating process have been explored in this research. This study serves as a pilot study to complement research on the thermal behavior of conductive thermal textiles and thermal control of thermal textiles. It provides guidance for precise temperature control for different situations.
Subjects: Hong Kong Polytechnic University -- Dissertations
Smart materials
Textile fabrics -- Thermal properties
Pages: xv, 131 pages : color illustrations
Appears in Collections:Thesis

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