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Science Forum Index » Chemistry Forum » sustained heating of polycaprolactone...
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| Julian Bradfield... |
 Posted: Sat Jun 21, 2008 3:48 pm |
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Guest
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I've been playing around with polycaprolactone (sold as Polymorph in
the UK, and I believe as Shapelock in the US), and noticed that its
properties change a bit on sustained heating above the melting point.
As usually used "at home", PCL is melted in water at a little above
60C, and as it melts it changes from bright white solid to transparent
putty. If you overshoot, and heat it to, say, 90C or so, it becomes
aggressively tacky (e.g. it will stick firmly to the glass of a
beaker), and not something you want to handle.
I've observed that if it's heated slowly (in water, over some hours),
it can be taken to 100C without becoming very sticky. Over this
time, it changes from clear to clouded, with a slightly creamy
colour. It remains highly malleable, but loses stickiness or tackiness
- I was able to handle a lump taken straight out of a boiling
beaker. When it solidifies, the colour remains slightly creamy,
compared with the quite pure white of the usual PCL. I don't see any
obvious change in the mechanical properties of the cooled solid,
compared to the usual state.
Can anybody tell me what is probably happening? My naive guess would
be that the polymer chains are shortening, but I don't know why that
might have the effects I observe.
From a practical point of view, a less sticky PCL could be useful, if
one is making casts of intricate objects.
(I would ask on sci.polymers, but that group appears dead and
spam-ridden, at least on my server.) |
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