"N Cook" wrote in message
...

Many thanks for the full reply.
I was totally unaware of the last point, so have added s.e.r as probably
a
lot there are unaware also.
Recently reminded me of this effect because a "rubbery" presumably soft
PVC
suspension inside a phono cartridge was leaching plasticizer and
softening
the surrounding hard plastic etc. I don't know if it is also related but
often if one "rubber" drive band in a VCR or audio tape deck perishes,
then
all the others are likely to fail in a sort of contagion -plasticizer gas
wafting around inside ?


You are quite welcome. Eastman Chemical Company, a former employer, made
both cellulosic plastics and a large number of plasticizers. I even worked
on a project to replace plasticized PVC in medical intravenous solution
bags with an elastomeric polyester because of the fears of plasticizers
leaching into the solutions (which they do!). While being more expensive
than PVC, our material was much stronger allowing thinner bags which offset
this higher raw material cost. But the perimeter radio frequency sealing
process required new equipment and the bag manufacturers were unwilling to
modify their manufacturing lines.

As far as VCR decks, I cannot think of any mechanism whereby the failure of
one drive belt via plasticizer migration would cause the others to fail
unless the plasticizer leaching from one belt actually dripped on another
belt. Remember that all belts were likely made at approximately the same
time, and had been in the VCR exposed to similar high temperatures for the
same time too.

--
73, Dr. Barry L. Ornitz WA4VZQ

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