Manufacturing of Fibres with New Reflective Properties and their Application in Textiles
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Manufacturing of Fibres with New Reflective Properties and their Application in Textiles Olivier T. Picot1, Mian Dai2, Ton Peijs1,2 and Cees W.M. Bastiaansen1,2 1 School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK. 2
Faculty of Chemistry and Chemical Engineering, Eindhoven University P.O Box 513, 5600 MB Eindhoven, The Netherlands.
ABSTRACT Reflective fibres were obtained in a two step process. First a core polyamide 6 fibre was spun from the melt and successively stretched. Then a chiral nematic liquid crystal coating was applied onto the surface of this fibre and further cured under UV light. The liquid crystal alignment was controlled by the molecular orientation of the polymer fibre and the 10 mm thick mono-domain coating presented a periodic helical organisation with a pitch of 350 nm. The obtained fibre showed strong Bragg reflection giving an intense green colour changing upon viewing angle. The fibre has been integrated into a fabric suggesting its application for textile design, fashion, and apparel. INTRODUCTION Colours have been present in fibres since the early use of textiles and fabrics. Conventionally, organic and/or inorganic dyes or pigments are use to generate the colour based on selective wavelength absorption of visible light. Such fibres present a single, angular independent colour. However colours can also be produced based on the interference of reflected light[1]. This mechanism is widely used in Nature and gives very vivid and intense colour that change upon the viewing angle such as seen in butterflies, birds or beetles [1,2]. In this case, the colour originates from the interaction of light with sub-micron periodic structures present at the surface of the feathers or the exoskeleton of the animal or insect. In the last decade several techniques have been developed to produce structural colour in fibres based on interference of light. Iohara et al. produced a fibre mimicking the effect of the Morpho butterfly [3]. The crosssection of the fibre consists of an alternate layered stacking of two polymers with different refractive index acting as a dielectric stack. The colour was controlled changing the thickness of the layers. A similar approach was used by Fink and co-workers to produce a photonic band gap yarn [4]. Here a fibre was obtained after a three step process involving arsenic triselenide As2Se3 deposition onto a poly(ether sulfone) (PES) film and drawing the fibre from a drawing tower, as it is done for optical fibres. Although the fibres obtained show very unique optical properties their application into textile is not straight forward as the process is relatively complex. In this paper a new approach is presented for the production of reflective fibres. The concept is based upon a bi component fibre composed of a classic fibre core such as nylon or polyester with a self organizing liquid crystal (LC) coating that gives the unique optical properties to the fibre.
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Chiral nematic liquid crystals are characterized by
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