I am attempting to make a critical point demonstrator (which will then be
sent to AJP's Apparatus Notes section for those who want one too).
I'm having a problem. The high pressure CO2 (about 1000 psi) attacks the o-ring
material. I have tried both buna-n and viton o-rings and they are both
permeated with the CO2 and do some pretty wild expanding and "popping."
I did a web search to find out what I could and got very little. (LOTS of stuff
on the space shuttle o-rings though!)
Some fire extingushers use CO2, what kind of o-rings do they use?
There is a device called a "critical point dryer" that is made for sample
prep for electron microscopes (SEM), what do they do?
Anyway, I have two questions:
1. Anyone know what kind of o-ring elastomer is not attacked by CO2?
2. Does anyone have a SEM that also has a "critical point dryer" with it. The
cpd is usually used for biological samples before gold coating, I'm told. I
would like to know the name (address and phone numbers would be wonderful) of
the company that makes the cpd. I want to ask them about both the o-rings and
the type of glass they use as windows.
Thanks for any help in advance.
John Sohl, Associate Professor, Department of Physics
Director, Layton P. Ott Planetarium
Weber State University, 2508 University Cir., Ogden, Utah, USA 84408-2508
voice: (801) 626-7907 FAX: (801) 626-7445
JSOHL@WEBER.EDU