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Textiles, Bleaching and Dyeing

Textiles, Bleaching and Dyeing. An Introduction. Textiles. Ancient craft using natural resources (wool, cotton, flax) for making fabric for clothing, shelter, bedding, floor covering, ... Mechanical aspects: picking, cleaning, carding, spinning, weaving and making final product.

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Textiles, Bleaching and Dyeing

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  1. Textiles, Bleaching and Dyeing An Introduction

  2. Textiles • Ancient craft using natural resources (wool, cotton, flax) for making fabric for clothing, shelter, bedding, floor covering, ... • Mechanical aspects: picking, cleaning, carding, spinning, weaving and making final product. • During the Industrial Revolution, the textile industry rapidly expanded and advanced technologically.

  3. Industrial Revolution • New inventions were assisted by the patent process, availability of investors, preventing knowledge to leave Britain. • Advances in power: manual, water, steam engines. • Growing sources of natural resources and markets (colonies). • Improving transportation infrastructure.

  4. Textiles: Bleaching • Bleaching fabric whitens it. • Pre-IR: wash in soap, boil fabric in strong base (lye soda ash; also NaOH), expose to sunlight. • Transition to Palaeotechnic: soak in weak acid (sulphuric and hydrochloric), and then base (lime, alkali). • Palaeotechnic: use of chlorine as bleach (Berthollet and Scheele, France , 1785)

  5. How Does Bleach Work? • Bleach oxidizes compounds (stains, dye, germs) by breaking chemical bonds and inserting oxygen or by converting C=C and/or C=O double bonds to single bonds.

  6. Chemistry • 1785 H2SO4 + 2NaCl  Na2SO4 + 2HCl Vitriol + common salt  2HCl + MnO2 Cl2 + MnO + H2O muriatic acid + black calx of Mn  • H2O + Cl2 (aq)  2H+(aq) + Cl-(aq) + OCl-(aq) Water + chlorine  hydrogen and chloride ions and HYPOCHLORITE ion

  7. Textiles: Dyeing • Dyes give color to fabric. • The first dyes were from minerals or extracted from plants and animals. Most of the latter were organic molecules (primarily C and H). • Indigo was one of the earliest organic dyes.

  8. Chemical Questions • As advances in textile production and bleaching were made, interest in fabric dyes increased: studying its chemical composition, improving extraction methods, modifying chemical composition to produce different dyes, discovering ways to make the dyes more colorfast , minimizing toxicity...There was a rich chemistry involved in these investigations.

  9. From Natural Dyes to Synthetic Dyes • The next logical step was to make dyes from chemicals in the lab or manufactory. • The first dye was synthesized by Perkins (an 18 year old lab assistant in London) in 1856: Tyrian purple, mauve or maureine. • This grew out of the products of the coal tar industry, one of which was aniline. • These dyes are organic compounds.

  10. Synthesis of the Dye called Mauve • REACTANTS: C6H7N + K2Cr2O7 + C7H9N + H2SO4 aniline + potassium dichromate + p-toluidine + sulfuric acid • PRODUCTS: a complex mixture of at least four methyl derivatives (C24 to C28) with a 7-amino-5-phenyl-3-(phenylamino)phenazin-5-ium core. http://www3.interscience.wiley.com/journal/121359283/abstract?CRETRY=1&SRETRY=0 • Products first verified in 1994 with more work in 2007

  11. Mauveine

  12. Chemical StructuresAniline and Toluidine

  13. One Structure of Mauveine

  14. Chromophores • The C =C bonds in the dye absorb light in the ultra-violet (λ < 200 nm) and visible (λ = 200-700 nm) region of the light spectrum causing the dye molecule to go from a ground state to an excited state. When the molecule returns to the ground state, visible light (λ = 450 nm; purple; ) is emitted and observed. • These molecules are called chromophores (chrom = color).

  15. Visible Light Spectrum • http://images.google.co.uk/images?q=visible+spectrum&ie=UTF-8&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&sa=X&oi=image_result_group&resnum=4&ct=title • 400 nm = violet; 500 nm = green; 575 nm = yellow; 700 nm = red

  16. Dyes – Fabric Bond • Dyes must adhere to the fabric. There are two mechanisms • The formation of chemical bonds between the fabric and dye. • The use of a third compound (called a mordant like alum) to form an insoluble compound with the dye. This product then adheres to the fabric.

  17. References • http://potency.berkeley.edu/chempages/ANILINE.html • http://www.chemsynthesis.com/base/chemical-structure-3482.html • http://www.rsc.org/Publishing/ChemScience/Volume/2007/06/mysteries_mauve.asp

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