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Elizabeth Henderson
Product Development Manager ITAC Ltd |
Silver was formerly seen every day in our pockets – although
it has been superseded in British coins it still works in many other contexts. Its
ductility and malleability means it has been used since ancient times to make
jewellery, ornaments and luxury items. At Itac we exploit its properties as a
biocide – silver ions when in contact with bacterial DNA prevent its
replication and appear to do this by interrupting the S-S bonds in the
molecule. We can incorporate small amounts of silver containing compounds in
coatings to exploit this effect. Silver nitrate in a block or as a solution was
applied to skin infections to kill the bacteria in the nineteenth century, but
in the twenty-first silver nanoparticles have been developed for use in textile
medical dressings.
In other parts of the chemical industry, silver has been
used as a catalyst for production of ethylene oxide and formaldehyde, particularly
for ethylene oxide which is used as a building block for polyesters (step to
polyurethanes). Itac uses these catalysts indirectly as we use a number of
polyester PUs in our products for textiles.
The photosensitivity of silver was exploited to make pictures
from early developments in the 1830s until the present day, although its use
diminishes as digital photography improves. Colourless silver ions are reduced
to black particles of silver metal by visible light, and will form a ‘shadow’
of a pattern placed between the silver ions and a light source. Over this time,
the technology for using silver was refined from silver nitrate solution on a
glass plate to emulsions of silver nitrate in gelatine on a flexible film.
Silver-containing materials also play a major role in
everyday electrical items due to its excellent conductivity. Inks formulated
with silver are used to produce printed circuit boards and other items such as
contact films beneath computer keyboards. The heating elements on car rear windows
are made of silver-based ink to conduct both electricity and heat across the
glass.
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