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THE CHEMISTRY OF THINGS
With the arrival of rainy days,
they are back out of the closets.
And with them, another of the comforts we have to thank to the developments of chemistry.
Today we are going to talk about...
...water proof clothing!
Its origin goes back at least to the 13th Century,
when South American natives covered their clothes with latex
to make them waterproof
Europeans imported the idea, but its success was not immediate:
the first waterproof clothes were heavy, uncomfortably hard and,
because of the solvent used to spread the latex on the fabrics,
they were very smelly!
The development of polymer chemistry
allowed them to become lighter, more flexible and odourless.
But the most remarkable quality of modern waterproofs
is that they also allow the skin to breathe;
that is, they prevent rainwater from getting in,
but allow water vapour released by perspiration to go out.
This effect is achieved by creating structures with tiny pores,
through which drops of water can't pass, but through which isolated water molecules easily can.
The modern airy waterproof fabrics are made with two layers of polymers with different properties:
a first layer of a micro-porous polymer that is hydrophobic,
i.e. it repels water, and a layer of polyurethane, turned inwards, closer to the skin
and which is hydrophilic i.e. it attracts water,
and absorbs the humidity that is released from the skin.
Then a bit of thermodynamics come into play:
the difference in temperature between the inside and the outside creates the necessary conditions
for the water molecules absorbed by the polyurethane to be pushed to the outside.
If you wear a waterproof coat and feel like you're in a sauna,
then it is because you're still not taking advantage of the developments of the chemistry of polymers.
To know more about the chemistry of waterproof clothing
visit our website aquimicadascoisas.org
or look for us on Facebook.