Multi-functional protective nano-finishing of textile materials

Abstract

The history of textiles and fibres spans thousands of years, with the materials changing from animal skins and leaves in early days to the plethora of yarns and fabrics today. Not until around 70 years ago, the textile industry underwent the most revolutionary changes and evidenced the most remarkable innovations in its history. The industry also made a great impact to many aspects of the society. Conventional textile finishing treatments have relatively long history and are well established. However, with the ever - increasing demands from the consumers and the society, the conventional treatments are unable to cope with these demands since many of them alter or harden the hand, some of them have harmful effects to human and cause pollution to the environment. New technologies in material science need to apply to the traditional textile industry to develop and produce high value added products and overcome the problems associated with the conventional finishing treatments. This PhD project represents a new and innovative approach to the functional, protective and intelligent finishing of textile materials with the use of the latest developments in nanotechnology. The enhanced end - use performance and the more environmentally friendly nanotechnology treatments that has been attempted to develop would undoubtedly improve the competitive edge of the textile and clothing industry in Hong Kong and beyond. To bridge the high - tech gaps, many attempts both in advanced materials, chemical synthesis approaches and finishing applications on fibrous substrates have been conducted throughout the thesis. Mainly, two systems have been investigated, i.e. ZnO and Au/Chitosan, respectively. Firstly, an effective growth approach to grow oriented hexagonal ZnO nanorod arrays onto various flexible fiber substrates is reported. The synthesis art combined the dip - coating process and self-assembly art in aqueous solution. The typical one - dimensional (1 - D) nanorods synthesized in this study were 10-50 nm in diameter and 300 - 500 nm in length. Secondly, further study has shown that structurally unique meso-scale dumbbells grown in aqueous solution were discovered for the first time with the length of 2.1 um , diameters of 700 nm, 800 nm, 450 nm in a smaller and larger end face, and in the waist, respectively. The typical dumbbell - shaped ZnO was 500 nm to tens of micrometres in length and 200 nm up to 1 um in diameters. The UV - Blocking property of the as-prepared ZnO dumbbells revealed a high UPF (UV protection factor) of 1000 and demonstrated a breakthrough of more complete blocking UV range (400 - 280 nm) than that of ZnO nanosols (352 - 280 nm), nanorods (375 -280 nm), and anatase titania films (332 - 280 nm). The 1 - D ZnO used in textile field is novel and this pioneering work has implication to fields such as aircrafts, vehicles, windscreens, glass windows, screens, curtains, outdoor products, and aircrafts. Thirdly, a bionic fabric surface: self - assembled monolayers film of functional alkyl silanes modified silica on oriented growth of ZnO crystals was fabricated. The subsequent silica sol treatment furnished the durable wettability. The water CA was decreased to 128o, 120o, 114o, and 110o, and water spray test rating was 100, 100, 90, 90 after 5, 10, 15, 20 cycles, respectively. Accordingly the oil repellency decreased from 7 to 5 after 20 cycles washing. The durable wettability of the coating after repeated washing was contributed to the linking ability of GPTS and F13 that promoted strong adhesion to the cotton fabrics and the low energy surface of as-formed films. Finally, a chitosan fiber as core and gold as sheath structural organic - inorganic composite was presented via a facile and eco-friendly approach. The chitosan fibers used in this study were 50 nm - 5 um in diameters and up to hundreds of micrometers in lengths. Gold shells were typically 20 - 50 nm in depth and their lattice fringes obliquely intersecting at an angle of 60o were displayed. The formation mechanism of as-fabricated chitosan fiber core with gold as shell structural composites was also schematically discussed. The surface plasmonics (SPs) of Au nanoshells and relative impact factors on SPs have been investigated. It has furnished the possibilities of multi - chromism in intelligent fabrics such as camouflage.