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Study on the Heat Absorption Effect of Fabrics and Clothing Technologies with Thermal Regulatory Fea

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Tutor: LiJun
School: Donghua University
Course: Fashion Design and Engineering
Keywords: heat absorption,thermal regulatory,PCM,ventilation,clothingfunctional design,the
CLC: TS941.4
Type: PhD thesis
Year:  2013
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Nowadays, the global warming has been recognized as a global issue which is attributed much to the development of the economy. This means that human beings will be exposed to a more hazardous environment. Especially for these industries, such as firefighting, bio-chemical disposing, military, and the athletes, they are more susceptible to the warming environment. In such a situation, clothing is required to provide more protection than ever before.Clothing, regarded as the second skin for human beings, plays an important role in thermal regulation. In modern society, it has been a trend that those clothing with temperature regulatory property is preferred. These clothing has been nicknamed smart clothing. They combine material technologies and clothing functional design technologies. This thesis was started under this background. The aim was to study the thermal regulating performance of two types of smart clothing. One was the clothing with phase change materials (PCMs); the other was the clothing with ventilation fans. They were studied in three thermal environments:extremely hot environment, hot environment and moderately hot environment. The small fabric sample testing, thermal manikin evaluation and human subject trials were used for various studying approaches. The main content and the chief conclusions are listed as follows:1. PCM microcapsules were used to treat cotton fabrics by a coating method. The treated fabrics were tested for their surface morphology, heat absorbing capability, air and water vapor permeability and heat transfer properties as well. It was shown that the treated fabrics became less air and water vapor permeable as the PCM load increased. Their heat absorbing capability increased with the PCM loading. Thermal resistance of the treated fabrics had no linear relationship with the PCM loading. It was affected by many factors, such as the fabric thickness and the static air trapped inside the fabrics.2. The treated fabrics were applied in a firefighter clothing fabric ensemble. They were used as the inner layer next to the skin. The thermal protective performance of these fabric ensembles were tested on a TPP Textile Protective Performance Tester. It was shown that with the PCM treated fabrics as the inner layers the protective performance of the mule-layered fabric ensembles increased a lot. The time to reach a second degree burn was decreased. The higher loading of the PCMs the better thermal protective performance could be obtained. PCM treated fabrics with a higher melting temperate could provide better thermal protective performance.3. Solid-liquid PCMs are usually encapsulated into packs and these packs are inserted into clothing to form PCM clothing. This PCM clothing with gel coolants was used in steel worker protective clothing for alleviating heat stress. A dry heated thermal manikin was used to identify its cooling power in a hot environment with strong radiation. It was revealed that local body parts of the thermal manikin covered with PCMs had lower skin temperature. Working time in the hot and radiative environment was prolonged. Yet it was also noticed that PCM clothing added much insulation to the wearers and hampered sweat evaporation. Therefore, in the next stage two hot environments with different humidities were tested for the PCM clothing¡¯s cooling power. A sweating heated manikin was used as a tool. The results showed that in the hot humid environment the PCM clothing could contribute to effective cooling, but in the hot dry environment the PCM clothing could just bring negative effect. PCM clothing with lower melting temperature could provide higher cooling power in the hot humid environment, when sweat production was high.4. Different with the PCM clothing, the clothing with ventilation fans could enhance sweat evaporation. A series of ventilation clothing with fans placed at different torso sites were designed. They also had different clothing openings. A sweating thermal manikin was first used to evaluate their cooling power under a hot environment. It was revealed that the fan locations and clothing openings had significant effect on local body cooling (p<0.05), but for the whole torso cooling and the whole clothing dynamic evaporative resistance, these two design factors had no significant effect (p>0.05). When the fans were placed at a local body part, that part underwent the highest cooling effect. Next, the ventilation clothing was evaluated by human subject trials in a hot environment. Office work with sedentary postures was simulated. The ventilation clothing decreased the chest and the scapular temperatures significantly (p<0.05). The cooling power was conspicuous just during the initial ventilation moment.5. The thermal regulating mechanisms of the PCM clothing and the ventilation clothing are different. The former cools the body by absorbing heat during the phase change process in which dry heat loss performs, whereas the latter cools the body by improving sweat evaporative cooling in which mainly wet heat loss performs. Therefore, these two types of clothing were tested in a moderately hot environment for cooling power. They were tested post exercise by human subjects. It was shown that both clothing decreased the heat strain, especially local skin temperatures on the torso were decreased significantly. The two clothing showed no significant difference on core temperature, heart rate and sweat production (p>0.05). The PCM clothing decreased the under clothing6. temperature and the clothing surface temperature much more than the ventilation clothing, but the clothing micro-climate humidity was increased by the PCM clothing. The ventilation clothing, however, decreased the clothing micro-climate humidity.Many topics were investigated in this dissertation. The chief conclusion could be summarized as follows. Using PCM microcapsules to treat cotton fabrics could change the physical properties of the fabrics and give the fabric thermal regulatory capability. Appling these PCM treated fabrics in firefighting protective clothing ensembles could improve the clothing ensemble¡¯s thermal protective performance. PCM microcapsules treated fabrics had very limited thermal regulating capability due to the loading limitation. However, using PCM packs in clothing could decrease heat strain and increase working time in hot environments due to the large loading amount. This type of PCM clothing, however, increased clothing evaporative resistance to a large extent and deteriorate evaporative cooling. Different from PCM clothing, the ventilation clothing with fans could enhance evaporative cooling. Their cooling effect was determined by the locations of fans and clothing opening design factors. When both type of clothing were employed in a moderately hot environment, both contributed to some effective cooling.This dissertation combined much knowledge from different disciplines, such as material technology, clothing ergonomics, physiology and psychology. The studying methods and results could be used as theoretical reference when developing smart clothing.
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