[sdiy] D-70 red goo of death - polyurethane?

[Robin Whittle]

Hi David,

My only guess is that the red material may have been a polyurethane
compound, perhaps to glue the weights into the keys.  Polyurethanes can
turn to crap of their own accord, relatively suddenly, after long
periods of time.

Spandex (Lycra) is a polyurethane material which is very stretchy - but
in a particular garment it can all turn to stiff, brittle, stuff within
some time period such as a year or so, when the garment is 10 or more
years old.

Clear, firm, self-adhesive "rubber" (not really) feet are made of
polyurethane.  I had two in my van, on the remote (wired) volume and
power control box for the sound system.  I affixed them in 1985.  Last
year, both of them turned into a horrible sticky mess.  They were close
together but not in a sealed environment, other than being inside the
vehicle.  I don't know of any solvent which will touch it.  They were
still firm enough to scrape off, but some residue remains for which
there is no obvious method of dissolving.  While these clear
self-adhesive feet are attractive, I think it is better to use real
rubber feet with screws in the middle if you care about how the machine
will be in its dotage.

Most resilient foam, as used in seat cushions and for lining carry
cases, road cases etc., is polyurethane foam.  I had some in a road case
for a bass guitar and one year (it was at around 20 years old) it all
turned into a horrible sticky mess - fortunately the guitar was not inside.

I understand that this material can degrade and produce a byproduct of
the degradation which itself catalyses the reaction.  I think this is a
gas or a volatile liquid.  So if there is a particular kind of
polyurethane in a sealed environment, it will all tend to go bad
together.  I recall reading that higher temperatures and humidities are
likely to facilitate this reaction.

The only reference I have in my Bookmarks is is:

  The degradation of polyester polyurethane: preliminary study of
  1960s foam-laminated dresses

  Doon Lovett and Dina Eastop    University of Southampton 2004


http://www.iiconservation.org/archive/www.iiconservation.org/publications/pdffetch0a03.pdf?pub_id=139

As far as I know, there's no degradation of "Estapol" and similar hard
polyurethane sealants for wooden floors and the like.

  - Robin