Fusion Message Board

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Subject: Re: QUESTION: metal to glass seals and teflon
Date: Nov 14, 8:38 pm
Poster: Dave Cooper

On Nov 14, 8:38 pm, Dave Cooper wrote:

>Finally how usefule is teflon for vacuum seals??? I realise it kind of flows under compression, but would it work if it was a fat, square cross section 'O' ring and located in grooves?.
Teflon PTFE - comes in two types - sintered and extruded. It is not easy to them apart. The sintered form is quite porous, whereas the extruded is not.

As to suitability for vacuum purposes, dont forget Viton O rings which ARE a fluorocarbon rubber. I have made a few things for high vacuum work out of thick PTFE plates and they worked okay to about the minus 7's vacuum. But there is the outgassing issue and temps need to be below about 150C for good performance.

Many thanks to Dan for a good summary of issues and techniques and nice listing of glass -metal references.

Dave Cooper