Chemistry Question #725

Joe Joe, a 13 year old female from Scarbrough asks on March 25, 2002,

What is the chemical reaction involved when dyes attach to cotton fibres? Is there any difference in how this works with natural or synthetic dyes?

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The answer

Barry Shell answered on March 27, 2002

I'm not sure what the difference might be for synthetic or natural dyes. A quick websearch yielded something on fiber reactive dyes which are synthetic dyes that attach permanently to cellulose fibers using a covalent (electron-sharing) bond. These molecules carry a "chromophore" which absorb varying spectrums of the light, allowing only certain spectrums to reflect.

Covalent bonding is the one of the most basic and strongest types of chemical reactions. This reaction happens gradually over time depending on temperature and/or the Ph level of the surrounding environment.

Other synthetic and natural dyes may adsorb to cotton fibres in various ways that are not as strong. There is a great deal available online if you use to search for terms like: dye chemistry introduction.

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