Presentation on theme: "Textiles, Bleaching and Dyeing An Introduction. Textiles Ancient craft using natural resources (wool, cotton, flax) for making fabric for clothing, shelter,"— Presentation transcript:
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. During the Industrial Revolution, the textile industry rapidly expanded and advanced technologically.
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.
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)
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.
Chemistry 1785H 2 SO 4 + 2NaCl Na 2 SO 4 + 2HCl Vitriol + common salt 2HCl + MnO 2 Cl 2 + MnO + H 2 O muriatic acid + black calx of Mn H 2 O + Cl 2 (aq) 2H + (aq) + Cl - (aq) + OCl - (aq) Water + chlorine hydrogen and chloride ions and HYPOCHLORITE ion
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.
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.
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.
Synthesis of the Dye called Mauve REACTANTS: C 6 H 7 N + K 2 Cr 2 O 7 + C 7 H 9 N + H 2 SO 4 aniline + potassium dichromate + p-toluidine + sulfuric acid PRODUCTS: a complex mixture of at least four methyl derivatives (C 24 to C 28 ) with a 7-amino-5- phenyl-3-(phenylamino)phenazin-5-ium core /abstract?CRETRY=1&SRETRY= /abstract?CRETRY=1&SRETRY=0 Products first verified in 1994 with more work in 2007
Chemical Structures Aniline and Toluidine
One Structure of Mauveine
Chromophores The C =C bonds in the dye absorb light in the ultra-violet (λ < 200 nm) and visible (λ = 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).
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.