Author: Ng, Pui Fai
Title: Investigation on natural and man-made hollow fibres for functional applications
Advisors: Fei, Bin (ITC)
Xin, John H. (ITC)
Degree: Ph.D.
Year: 2019
Subject: Hong Kong Polytechnic University -- Dissertations
Plant fibers
Textile fibers
Department: Institute of Textiles and Clothing
Pages: xxii, 201 pages : color illustrations
Language: English
Abstract: Nowadays, core-sheath fibres of which fascinating properties can be assembled into a single fibre are currently utilised in various fields. However, only few studies have focused on the preparation of functional textile fibres with core-sheath configurations. For this reason, this work lays down two approaches, by which natural textile materials, kapok fibre and silk fibroin, were converted into photoluminescence core-sheath fibres for advanced textile applications. Kapok fibre, a natural fibre possessing hollow tubular structure, has been selected to prepare luminous microtubes. A facile and general biomimetic mineralisation method was employed to introduce tungstate-based nano phosphors into kapok lumens. The hydrophobic nature of kapok fibre enables the formation of a uniform phosphor layer on the internal surface. Thorough characterisations of the crystal mineralisation and fibre properties were achieved by various characterisation methods. The resultant fibres achieved a high particle loading over 100 % of the kapok substrate. They exhibited stable red emission under UV irradiation, having potentials for applications in flexible optical devices and anti-counterfeit products. Silkworm silk, another natural textile fibre, was proposed to regenerate into core-sheath fibre by means of microfluidic spinning. Prior to fibre formation, a microfluidic device was prepared through template moulding technique using a highly stretchable gel material. The inherent characteristics of gel template supported replica moulding inside PDMS matrix with different architectures. The resultant microchannels exhibited high surface quality under SEM observation. The as-prepared microfluidic Y-junction device was subsequently used for regenerated silk fibre spinning. However, it was less applicable in preparing uniform filament with core-sheath structure due to fluid leakage at the spinneret-channel connection under high-pressure extrusion. Therefore, regenerated silk-based fibre, consisting of iota-carrageenan/polyacrylamide (τC/PAAm) gel core and silk fibroin/polyurethane (SF/PU) sheath, was prepared by commercial instrument - coaxial metal spinneret. These core-sheath fibres were characterised on morphology, secondary structure, and mechanical properties. Fibres fabricated at sheath concentration of 17 wt% showed the most uniform morphology with circular cross-section. Conformational changes of SF from random coil to ß-sheet structure were encouraged by fibre coagulation and post-drawing, as indicated in XRD analysis and Fourier transform infrared spectroscopy (FTIR). The resultant fibres with proper processing conditions displayed excellent mechanical properties, being suitable in preparing various functional textile materials. Moreover, the fabrication of continuous near-infrared-emitting fibres has been demonstrated by incorporating long-lasting phosphorescent phosphor and fluorescent Ag2S quantum dots (QDs) into the regenerated silk-based fibre. Green-emitting phosphor was introduced into the fibre core during spinning, while various layers of QDs emissive in NIR range were deposited on the fibre surface. Fluorescence spectrometry confirmed that the green emission of the embedded phosphors was absorbed by the surface Ag2S layer to give continuous NIR emission in dark. This modified silk-based fibre supported self-warming properties without using electric circuits, allowing its applications in thermal textile and wearable phototherapy device. Photoluminescence core-sheath fibres have successfully been fabricated herein. The findings could help explore the way forward for the preparation of functional textile materials from natural fibres, which offer benefit to the textile industry and wide consumers.
Rights: All rights reserved
Access: open access

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