there has been a lot of news lately in
Britain and in Europe about silicones
that have been used for medical implants
particularly in women's breasts when
people talk about this in the media they
keep on muddling up
silicon and the element and silicones
which are the materials that are used
for these implants so it seem sensible
just to tell you what silicons
are
and silicones are a sort of plastic now
you probably all familiar with plastic
bags like this one that my lunch came in
today and these plastic bags are made of
carbon and hydrogen and so in here if
you looked under microscope you would
see a group of carbon and hydrogen atoms
joined together to make a wiggly chain
like this with the carbons bonded
together with these extra bits here
being hydrogen so you can see there's a
carbon carbon bonds and some hydrogen
sticking out now silicon the element
which is a crystalline material which
looks a bit silvery if you look at it is
in the same group of the periodic table
as carbon and in principle you could
make the same sort of chain with silicon
hydrogen compound but the problem is
that the bonds between two silicon atoms
are very weak and it was discovered a
number of years ago that you can make
much more stable compounds if you have a
silicon oxygen silicon Bond so there's a
whole family of plastics which involve
silicon oxygen silicon bonds with the
Silicon being bonded onto hydrogen or
sometimes onto carbon more usually they
have methy groups ch3 groups attached
here so you have very stable compounds
and they're particularly useful for
medical purposes because they're
chemically very very inert they don't
react with anything as you vary the
length of the chain the materials become
more and more viscous more and more
trickly this is silicone which is short
chain and you can see it looks rather
like water if you make a slightly long
longer
chain it becomes much more
oily and if you have a really long
chain it becomes so viscous look if I
turn this upside down and put it here
you can see it only slurps very very
slowly just like trial it's even
stickier the silicone
implants that have been used consist of
a bag made of silicone chains that have
been bonded together socaled
cross-linking so that they become a very
R flexible but strong material and
inside it is a much more liquidlike
material like that so that the
artificial breasts have a feel that is
quite similar to the Natural tissue
and the problem and the scare has been
because the material that has been used
in these um breasts is so-called
industrial grade now I don't know any
more than you do about the precise
nature of what these chemicals are but I
can explain to you what industrial grade
means whenever you make a chemical it is
impossible to make it absolutely pure
because they're just so many atoms you
can never get rid of the last atom of
some
impurity so when you're using a chemical
for a particular application you keep
the levels of impurity low enough so
that they don't matter if you're using
something for some industrial purpose
you're using silicone as a oil for
lubricating some piece of
Machinery one or 2% of something else is
not going to harm things but on the
other hand if it's going to be something
that you eat or put in your body you
have to make it very much purer so in
this case that's been in the news about
a particular batch of breast implants
from just one
manufacturer there is some out about
which grade of silicone was used in
those implants much of the argument at
the moment goes about with the fact that
some of these implants seem to be
rupturing that's breaking more
frequently than is normal for implants
and this may be
because the outer plastic is slightly
less crosslin than um those in the
better made um breast implants so
they're not quite as strong or perhaps
just the material was not as thick as is
used normally but the chemistry behind
it is really quite simple the material
that's used is chemically very inert and
is a polymer plastic with silicon oxygen
silicon
chains