On Fri, 14 Mar 2008 08:34:35 -0500, Randy wrote:
On Thu, 13 Mar 2008 21:56:41 -0700 (PDT), stans4... wrote:
On Mar 13, 11:27Â*am, Randy wrote:
Looking to replace a peice of 3/4" plywood with some type of plastic.
Application is in a heated press used to join rubber sheets. Â*Problem
with the plywood is it compresses in use, and as it gets thinner the
bolts used to hold the whole thing together start to stick out and the
unit requires frequent retorquing.

Need some type of plastic that does not compress like wood, can
withstand 350 deg F for 1 hour, and idealy would have a coeffient of
expansion close to aluminum.
....
The material has to be a thermal insulator as this sheet goes between
the heater plate and another sheet of alum., and somewhere in there is
an airbag to provide the force and some alum I-beams and tie bolts to
clamp the whole thing together. The airbags need the wood sheet to
limit the amount of heat they see.

I'll need to research the thermal conductivity of wood VS particle board
VS Al honeycomb.

Wafer wood or particle board are pre compressed in their manufacture so
that might be better, or the die-board or some other premium plywood
might be better.
....

Have you already tried cement fiber board, like Durock, WonderBoard,
and HardieBacker, or ceramic boards Fibrefrax and Micore?
Re insulation value, http://www.chimneysweeponline.com/horvalue.htm
lists Durock at .4 R-value per inch and the ceramics at 2.2.
Cement fiber board is low-cost (ca. $10 for a 3'x5'x.5" sheet) and
uncompressable until it breaks; the ceramics I'm not familiar with,
but think they might be 5x as much, and may compress easily.
-jiw