Fabric softeners form an integral part of most people’s washing routines |
Fabric Softeners
How Do Fabric Softeners Work?
Piyush Patel
Fabric softeners contain anionic compounds (positively charged compounds) that bind with the negatively
charged fabrics and nullify static cling, while the softness and scent is
provided by the deposition of fabric softeners over the external fibers.
Just as no meal
is considered complete without a dessert, no washing routine is considered
complete without the final rinse cycle that incorporates the fabric softener.
Through the
built-in dispenser in our washing machines or via Downy, the adorable dispenser
ball, fabric softeners are essential to keep our clothes soft as a cloud.
Also, as the
cherry on top, fabric softeners help our clothes smell fresh and fragrant.
Luckily, the list
doesn’t end there; using a fabric softener also helps to avoid static cling,
prevent wrinkles, make ironing easier, help fabrics retain color, etc.
The question is,
how does a mushy liquid used in generally tiny quantities achieve so
much? Hint: It’s all about chemistry!
Why are fabric softeners used?
The purpose of
using a fabric softener differs slightly depending on the method used for
drying (and sometimes washing) one’s dirty laundry.
While manually
washing clothes is not a common practice in western countries, the use of
mechanical washers puts a lot of stress on fibers, especially the fabric fibers
on the outer surface.
After washing the
clothes, one may either choose to dry them out in the sun or use a mechanical
drier, based on availability.
It is a
well-known fact that air-drying your machine-washed laundry gives a harsher
feel to the fabric, as compared to machine/tumble drying.
In the case of
air drying, fabric softeners are primarily employed to retain the original
softness of the material.
As for
machine-dried clothes that are already left softer, fabric softeners are used
to avoid static cling and give the laundry a pleasant scent.
Static cling, as
the name suggests, is the clinginess that develops in fabrics (and other items)
due to static electricity.
When in a drier
or a washer, each piece of fabric comes in contact with several other types of
fabric.
While in contact,
these materials rub and exchange electrons with one another, leaving each
article either electron-rich or electron-deficient.
Physically
separating these materials leads to the generation of an electrical charge, a
phenomenon known as triboelectric charging or the triboelectric effect (“tribo”
means rubbing).
The development
of static cling causes clothes to adhere/stick to the wearer’s skin, while also
acting like a dirt and dust magnet.
Composition & Function of Fabric Softeners
The softener
solutions of the early 1900s (manufactured to diminish the harsh texture left
behind from using primitive cotton dyeing processes) compromised water, soap,
and a specific type of oil in a well-defined ratio (7:3:1).
Advancements in
the field of organic chemistry led to the development of better alternative
compounds, such as quats, particularly dihydrogenated tallow alkyl dimethyl
ammonium chloride (DHTDMAC) and more recently, esterquats and polydimethylsiloxane (PDMS).
Quaternary ammonium cations,
more commonly known as quats, are essentially ammonium salts with a positively
charged nitrogen atom at their heart, bonded to 4 different organic compounds.
They can
therefore be divided into two halves, one that is a water-insoluble
(hydrophobic & fatty in nature) hydrocarbon end, and the other a
water-soluble positively charged head.
Since the
majority of a quat molecule is hydrophobic, emulsifiers are added to assist in
penetrating the wet fabric and for stabilization purposes.
Currently, there
are three different types of emulsifiers used in fabric softeners, namely
micro-emulsions, macro-emulsions, and emulsion polymers.
Each of these
emulsifiers is added based on the level of fabric penetration/deposition to be
achieved.
Micro-emulsions
allow for deep penetration into the fibers, while macro emulsions and emulsion
polymers only deposit on the outer surface.
Once inside the
fabric, the positively charged core of a quat neutralizes static cling by
bonding with the negatively charged fibers.
In the process,
the threads stand up and a molecule-thick coating of quats is deposited over
the external fibers.
This coating
essentially acts as a lubricating layer, owing to the fatty ends of the
hydrocarbon chain in quats.
The layer thus
contributes to a fluffier and softer feeling material, along with making
the ironing process notably easier.
Fabric threads when washed with detergent only vs when treated with detergent + fabric softeners. |
DHTDMAC, the traditionally used
quat in fabric softeners, degraded quite slowly, leading to environmental
issues, and was therefore superseded by a biodegradable alternative—esterquats.
However, esterquats also
possessed a few demons. The hydrophobic nature of the long hydrocarbon chains
in quats caused a decrease in the absorbing capacity of items like towels and
diapers.
Manufacturers later found their
solution in synthetic silicone compounds like PDMS, amine and amide silicones,
silicone gums, etc.
Another very
common question concerning softeners is why they can’t/shouldn’t be added along
with the detergent itself.
Since most fabric
softeners contain cationic compounds (compounds with positively charged ions)
and laundry detergents are anionic (compounds with negatively charged ions),
the two can react to form an unwanted precipitate.
However, the same
isn’t the case with anionic fabric softeners, which can be added to the
detergent itself.
Final words
Now, to
contradict my own words, using a fabric softener might not always be necessary
or advised.
People with very
sensitive skin are prone to dermatitis (skin inflammation) when wearing clothes
that have been treated with fabric softeners.
Unfortunately,
the ingredients in fabric softeners are also known to cause headaches and
lightheadedness, along with some other very serious health issues, such as
asthma and cancer.
Studies have
further revealed that clothes, after being treated with fabric softeners, are
also more susceptible to being set on fire.
From an
environmental point of view, softeners contain an ingredient derived from
animal fats, while many of the chemicals used in softening conditioners are
toxic and detrimental to marine life.
So, how can you
maintain the softness of your laundry without using harmful fabric softeners?
Try using wool or
aluminum foil dryer balls to get rid of static cling and DIY-ing your own
fabric softener by adding half a cup of vinegar to the final rinse cycle… and
don’t worry, it won’t stink up your clothes!
Piyush is a
mechanical engineer from Mumbai (India) who runs as much as his machines. He’ll
always be up to talk about comics, movies, and music. Will meet you annually at
the comic-con and daily at the gym.
https://www.scienceabc.com/eyeopeners/how-do-fabric-softeners-work.html
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