Comparison of new PEEK ® seals with traditional helicoflex for ultra high vacuum applications

Abstract

The use of engineering resins has increased dramatically in the last years and now the mechanical and chemical properties of the most recent products render these new materials excellent candidates for ultra high vacuum (UHV) applications. In particular, a relatively inexpensive polymer like PEEK ® can become competitive when vacuum seals have to be manufactured. In this paper, a systematic series of tests is described, aimed at comparing the properties of PEEK ® and traditional Helicoflex seals. Two different designs for the new PEEK ® seals were tested. Their performances were compared not only in cases of metal but also of glass plain surfaces. A complete temperature scan was carried out for both applications (metal and glass surfaces) up to 200°C. At room temperature the vacuum properties of PEEK ® seals are comparable to those of the more traditional Helicoflex gaskets. At higher temperatures the only significant drawback of the proposed PEEK ® prototypes is a significant He permeation. On the other hand, gaschromatographic-mass spectrometer analysis confirms that the outgassing of this material is compatible with UHV requirements. In the temperature range investigated, one of the tested solutions gives very positive results; given the lower cost and much easier handling of this prototype with respect to Helicoflex technology, the proposed design can be considered with great attention as a possible future replacement.