In message <[email protected]>, dated Wed, 13 Feb 2008, Grace Lin <[email protected]> writes:
>According to his explanation, Styrofoam is expanded polystyrene (EPS) >and it does not support heavy weight. How heavy is 'heavy'? In my experience, it will support heavy things with flat bases but it collapses under point loads, such as the 'feet' on equipment. > He has no idea of the dielectric constant. My question is: does any >one have dielectric constant information for Styrofoam and polyethylene? Solid polystyrene has a dielectric constant of around 2.6, but the foamed material has a much lower value. What it is, even Dow don't say.(;-) You can measure it roughly with some foil and a capacitance meter or bridge. It doesn't vary much with frequency, so you can use any convenient frequency. Cut a thin slice (of known, uniform thickness) about 100 mm square, cover each side completely with foil, suspend it in free air and measure the capacitance. The capacitance is C = kA/d, A is the area in square metres, d the thickness in metres and k is the absolute permittivity. So k = Cd/A. Divide k by 8.86 pF to get the dielectric constant. Polyethylene has a dielectric constant of 2.3. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
