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Title: Organosilicon-based in situ sol-gel technology for multifunctional textiles
Authors: Lu, Hai Feng
Degree: Ph.D.
Issue Date: 2015
Abstract: Fabric and clothing products with functional surface finishing treatments can achieve better end use properties. Functional textiles considerably improve the performance in a wide variety of applications and meet consumers' demands of comfortable and health care as well as protection against chemical,mechanical, thermal and biological attacks. The functionalization of textiles was well developed in the past decade, but there are still many disadvantages or challenges, for example, some of them have harmful effects to human and cause pollution to the environment. New technologies in material science need to be applied to the traditional textile industry to develop and produce high value added products and overcome the problems associated with the conventional finishing treatments. This research presents new and innovative approaches to functionalize textile materials based on organosilicon compounds via in situ sol-gel technology. The approaches developed here are to form micro-nanocomposite assemblies directly on fiber surfaces and impart multifunction to textile substrates in an environmentally friendly way. Up to now, water repellent function continues to take a large share in the functional fabrics market and is gaining universal acceptance. For this purpose, fluorocarbons with low surface energy are the important repellent agents and are widely used for textile finishing. But, the fluorine chemicals are mainly based on perfluorooctanoic acid (PFOA) derivatives. There are some evidences concerning possible persistence, bioaccumulation, and/or toxicity of these types of fluorocarbon chemicals in the environment, which make them less and less desirable in industrial applications. In this project, a non-fluorinated water-based hybrid organosilicon miniemulsion was prepared by using methyl trimethoxy silane (MTMS), 3-glycidyloxypropyl trimethoxysilane (GPTMS) and hexadecyltrimethoxysilane (HDTMS) under ultrasonication and a very small amount of surfactant. The as-prepared miniemulsion was applied on cotton fabrics by a conventional pad-dry-cure process. After padding, the wet fabrics were fumigated under ammonia atmosphere for in situ condensation of siloxanes on cotton fiber surfaces. The treated cotton fabrics have an artificial lotus leaf roughness structure and exhibit excellent water repellent property with 153.7° water contact angle and 100 in water spray rating, the water repellency can also afford 30 home launderings.Secondly, for some synthetic fibrous textiles, especially those after water repellent treatment, high specific resistance and low moisture regain lead to the static problem. The static electrical charges do not easily dissipated and result in the attraction to dust, electric shocks and even fire hazards. Anti-static treatment therefore becomes necessary. Most antistatic agents can decrease static charge accumulations because of its hydrophilic property by absorbing water from the air. But, these moisture-absorbing coatings will undermine the hydrophobic property. This project succeeds in combining carbon nanotubes (CNTs) with hydrophobic HDTMS to achieve both water repellent and antistatic properties for polyester fabrics via in situ sol-gel method. CNTs in this system act as not only antistatic agent but also micro-rough structure building agent.What's more, the mechanism of CNTs as an antistatic agent does not have adverse effect on the water-repellent property. The treated polyester fabric with "micro-wrinkle" structure shows excellent water repellency and antistatic properties, as well as good wash fastness.
Thirdly, this project also presents the preparation of a formaldehyde-free and halogen-free UV-blocking and flame-retardant hybrid coating for cotton fabric via in situ sol-gel method. Cotton as the most important natural fiber is widely used as clothing material, but very ease to thermal degradation, ignition and burning. Flame-retardant (FR) treatment of cotton is very important for preventing fire and protecting human life. However, the most efficient and widely used halogen-based FR compounds can produce a large amount of smoke and toxic gases during the combustion process. Some of them were even banned by USA and EU. Some phosphorous-based compounds including N-methylol dimethylphosphono propionamide (MDPA) and tetrakis hydroxymethyl phosphonium chloride (THPC) and are widely used as halogen-free FRs.However, these types of FRs also have the disadvantage of formaldehyde release. Formaldehyde is a well-known carcinogen compound confirmed by the World Health Organization.In this project, a hybrid sol was prepared based on tetraethylorthosilicate (TEOS), GPTMS and Mg(CH₃COO)₂. The as-prepared hybrid sol was used for cotton fabric treatment by a conventional dip-pad-cure process. The padded cotton fabric was also put into ammonia atmosphere for in-situ deposition and condensation of Mg(OH)₂/silicon assemblies on cotton fibers. The vertical flammability and ultraviolet protection factor (UPF) testing results showed that this uniform Mg(OH)₂/silicon composite coating acting as a physical barrier can achieve excellent flame-retardant and UV-blocking properties. The research works presented in this thesis are focused on an organosilicon-based in situ sol-gel technology to treat textile materials with multifunctions. The nano-microcomposite coatings were directly in situ prepared on fiber surfaces for multifunctions, synergistism and durability. The chemical systems prepared in this project can bring high performance and added value to the textile products, while at the same time have minimal impact to the environment. The methods developed in this project can also provide generic approaches for textile chemists in functionalization of textiles or other flexible substrates, and are of highly potential for industrial mass production.
Subjects: Textile finishing.
Textile finishing agents.
Hong Kong Polytechnic University -- Dissertations
Pages: xxi, 186 pages : color illustrations
Appears in Collections:Thesis

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