Unit - Chemistry of Textiles: Treatments
- Dry Cleaning
- Flame Retardants
Felt is a non-woven cloth that is produced by matting, condensing
and pressing woollen fibres. While some types of felt are very
soft, some are tough enough to form construction materials. Felt
can be of any colour, and made into any shape or size.
From the mid-17th to the mid-20th centuries, a process called
"carroting" was used in the manufacture of good quality felt for
making men's hats. Beaver, rabbit or hare skins were treated with
a dilute solution of mercuric nitrate,
[Hg(NO3)2]. The skins were dried in an oven
where the thin fur at the sides turned orange - giving rise to
the name. Pelts were stretched over a bar in a cutting machine
and the skin sliced off in thin shreds, the fleece coming away
entirely. The fur was blown onto a cone-shaped colander, treated
with hot water to consolidate it, the cone peeled off and passed
through wet rollers to cause the fur to felt. These 'hoods' were
then dyed and blocked to make hats. This toxic
solution and the vapours it produced resulted in widespread cases
of mercury poisoning among hatters,
possibly giving rise to the expression "Mad as a hatter".
Videos showing how Stetson or
Akubra hats are made.
is a 3M brand of products, that act as a
stain repellent and durable water repellent when applied to
fabric, furniture, and carpets, protecting them from later
The original formula for Scotchgard was discovered accidentally
in 1952 by 3M chemists Patsy Sherman and Samuel Smith. Sales
began in 1956, and in 1973 the two chemists received a patent for
Two related "key ingredients" of Scotchgard are perfluorooctane
sulfonate (PFOS) and perfluorooctanesulfonamide
(PFOSA), a PFOS precursor. In May 2000, under USEPA pressure,
3M announced the phaseout of the production of perfluorooctanoate (PFOA), PFOS, and
PFOS-related products. 3M had monitored
the efffect on health for some years.
In May 2009 PFOS was classified as a persistent organic pollutant (POP) by the
Since June 2003, after 3M reformulated Scotchgard it replaced
PFOS with perfluorobutanesulfonic
acid (PFBS). PFBS has a much shorter half-life in people than
PFOS (a little over one month vs. 5.4 years).
|The structure of perfluorobutanesulfonic acid (PFBS)
Dry cleaning is any cleaning process for clothing and textiles
using a chemical solvent other than water, that is, it is not
really dry just that they are not exposed to water. The solvent used
was typically tetrachloroethylene (perchloroethylene), which the
industry calls "perc". It was used to clean delicate fabrics that
could not withstand the rough and tumble of a washing machine and
clothes dryer; it can make labour-intensive hand washing
|The structure of tetrachloroethylene (perc)
Dry Cleaning Solvents
- Glycol ethers (dipropylene glycol tertiary-butyl
ether) (Rynex, Solvair, Lyondell Impress) are in many cases more
effective than perchloroethylene (perc) and in all cases more
environmentally friendly. Dipropylene glycol tertiary butyl ether
(DPTB) has a flashpoint far above current industry standards, yet
at the same time possesses a degree of solvency for water-soluble
stains that is at least equivalent to, and in most cases better
than, perc and the other glycol ether dry cleaning solvents
presently in commercial use. A particular advantage of the
DPTB-water solutions of the Rynex product in dry cleaning is that
they do not behave like a typical mixture, but, rather, the
behavior is the same as a single substance. This permits a
better-defined separation upon azeotropic distillation at a lower
boiling point, facilitates reclamation more effectively (at a
level of 99% or greater), and also enhances purification using
conventional distillation techniques.
- Hydrocarbon is most like
standard dry cleaning but the processes use hydrocarbon solvents
such as Exxon-Mobil's DF-2000 or
EcoSolv. These petroleum-based solvents are less
aggressive than perc and require a longer cleaning cycle. While
flammable, these solvents do not present a high risk of fire or
explosion when used properly. However hydrocarbon contains volatile organic
compounds (VOCs) that contribute to smog.
- Liquid silicone (decamethylcyclopentasiloxane
or D5) is gentler on garments than perc and does not cause color
loss. Requires a license be obtained to utilize the property of
GreenEarth Cleaning. Though
considerably more environmentally friendly, the price of it is
more than double that of perc and GreenEarth charges an annual
affiliation fee. Degrades
within days in the environment to silica and trace amounts of water and
CO2. Produces nontoxic, nonhazardous waste. Toxicity
tests by Dow Corning shows the solvent to increase the incidence
of tumors in female rats (no effects were seen in male rats), but
further research concluded that the effects observed in rats are
not relevant to humans because the biological pathway that
results in tumor formation is unique to rats. (170.6
°F/77 °C flash point).
- Modified hydrocarbon blends (Pure Dry)
- Brominated Solvents n-Propyl Bromide
- Perchloroethylene has been in use
since the 1940s, perc is the most common solvent, the "standard"
for cleaning performance, and most aggressive cleaner. It can
cause color bleeding/loss, especially at higher temperatures, and
may destroy special trims, buttons, and beads on some garments.
Better for oil-based stains (which account for about 10% of
stains) than more common water-soluble stains (coffee, wine,
blood, etc.). Known for leaving a characteristic chemical smell
on garments. Nonflammable. A recent study conducted at Georgetown
University shows perc, classified as carcinogenic to humans by
the EPA, is retained in dry-cleaned clothes and that levels
increase with repeat cleanings.
CO2 - Consumer Reports rated this method
superior to conventional methods, but the Drycleaning and Laundry
Institute commented on its "fairly low cleaning ability" in a
2007 report. Another
industry certification group, America's Best Cleaners, counts
CO2 cleaners among its members. Machinery is
expensive-up to $90,000 more than a perc machine, making
affordability difficult for small businesses. Some cleaners with
these machines keep traditional machines on-site for the heavier
soiled textiles, but others find plant enzymes to be equally
effective and more environmentally sustainable.
CO2-cleaned clothing does not off-gas volatile
compounds. CO2 cleaning is also used for fire- and
water-damage restoration due to its effectiveness in removing
toxic residues, soot and associated odors of fire. The
environmental impact is very low. Carbon dioxide is almost
entirely nontoxic, it does not persist in clothing or in the
environment, and its greenhouse gas potential is lower than that
of many organic solvents.
- Wet cleaning is a system that
uses water and biodegradable soap.
Computer-controlled dryers and stretching machines ensure that
the fabric retains its natural size and shape. Wet cleaning is
claimed to clean a majority of "dry clean only" garments safely,
including leather, suede, most tailored woolens, silk, and
rayon. Most perc cleaners use wet cleaning on some
garments, but there are only about 20 exclusive wetcleaners in
the United States.
|The structure of Decamethylcyclopentasiloxane (D5),
used in "GreenEarth Cleaning"
The term flame retardants includes a diverse group of chemicals that are
added to manufactured materials, such as plastics and textiles, and surface
finishes and coatings. Flame retardants inhibit or delay the spread of fire
by suppressing the chemical reactions in the flame or by the formation of
a protective layer on the surface of a material. They may be mixed with the
base material (additive flame retardants) or chemically bonded to it
(reactive flame retardants). Mineral flame retardants are typically
additive while organohalogen and organophosphorus compounds can be
either reactive or additive.
commercial demo for a Flame Retardant
Much of the information in these course notes has been sourced
from Wikipedia under the Creative Commons License. Students
taking this course will be expected to contribute to Wikipedia as
a part of their course assignments.
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The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica
Created February 2013. Links checked and/or last
modified 3rd November 2016.