Outgassing behavior of different high-temperature resistant polymers

Abstract

In vacuum applications, polymers often need to be used in spite of their relatively high outgassing rates, e.g., as sealing or spacer material. For some polymers—like Viton®, which is used for O-rings—data on outgassing rates can be found in literature, while for others, in particular, the most relevant ones that can be used at higher temperatures, only few results are available. Therefore, different high-temperature resistant polymers were measured at the Outgassing Measurement Apparatus, which uses the difference method. These polymers were polyimides like Kapton®, Vespel®, and Meldin®, as well as a polyetheretherketone and a polybenzimidazole. In order to investigate the temperature behavior of the outgassing of the polymers, the measurements were performed at room temperature, 100 °C, and 200 °C. The outgassing species were determined by a mass spectrometer. In addition, the dependence of the outgassing on the material thickness was analyzed. The paper shows that the outgassing rates of the examined polymers are higher than 10−4 (Pa m3)/(s m2) after 10 h at room temperature, except for the thin Kapton samples. Thus, further treatment of the materials will be necessary depending on the application. It is shown that a vacuum bake-out at not less than 200 °C is favorable. The main outgassing species is water, as expected, but also different hydrocarbons with higher mass can be seen for the polyimides. Concerning different thicknesses, the outgassing rate of a thin sample generally decreases more steeply than the outgassing rate of the thicker sample. Nevertheless, the steepest decrease was found for the thickest Kapton sample, with a difference of nearly factor 500 between 10 and 100 h at room temperature.

Effect of Three-Dimensional-Printed Thermoplastics Used in Sensor Housings on Common Atmospheric Trace Gasses

“…Meanwhile, for a baffle that is off-gassing, (Equation ( 1 )) will be negative (negative reaction rate). Previous studies using the pressure rise method to measure vacuum off-gassing of thermoplastics report the off-gassing rates per unit surface area [ 21 , 23 ].…”

Development of a New Electromagnetic Extraction Channel from the AGOR Cyclotron

“…Further more, PEEK was chosen because of its maximal tensile strength of 95 MPa, temperature range up to 250°C, low temp expansion coefficients and good vacuum properties. PEEK shows the best outgassing performance over time with respect to Vespel, PBI and Meldi [5].…”

Realization of the kilogram using the KRISS Kibble balance

“…The mass and surface area of the PEEK materials of the coil suspension are approximately 3 kg and 0.5 m 2 , respectively. The typical outgassing rates of the PEEK materials are larger than 10 -4 Pa m 3 s −1 m −2 and decrease over time [20]. Due to the outgassing of the PEEK material, the coil suspension loses mass at a rate of approximately 2 mg h −1 .…”