|Re: composition of calculator cases - Slightly OT|
Message #8 Posted by Juan J on 24 Feb 2007, 9:02 a.m.,
in response to message #6 by bill platt
Yes, it is a bit misleading. I was thinking of thermoplastics when I wrote my post.
Themoset polymers usually crosslink during polymerization, and the final product has a structure usually impervious to chemicals and/or the external environment. Instead of long polymer chains you have crosslinked chains that form a grid. Depending on the monomers you use, the end polymer can be either very tough or very flexible. And when heated, as you noted, they decompose.
About teflon, "decomposing" is not exactly what happens. Teflon is usually sintered (the powder is heated to about the melting point temperature) and when heated above the melting point, it first turns into long fluorocarbon chains that in turn become the monomer at about 900 degrees (I am getting the temperature from memory, and it may be wrong.) The process is interesting enough and has been researched extensively, but that is another story.
ABS is usually a combination of either polyacrylonitrile/polystyrene and polybutadiene or polystyrene/polybutadiene and polyacrylinitrile (again, I am taking this from memory, it has been a long time since my Polymer Science class, and I might be missing something) that yields a uniform terpolymer.
Another two cents, and please excuse my mistakes.