Check the Vapour Pressure!
When selecting a vacuum grease it is important to check the vapour pressures of your materials is suitable at your required temperature. If you have a range of temperatures, the most important temperature is the highest temperature. Vapour pressures across the working temperature range should be available from the manufacturer. You can view the vapour pressures of Apiezon greases by clicking Apiezon Grease Vapour Pressure
To check the vapour pressure of the grease you intend to use is below the vacuum at all temperatures, start by comparing the highest level of vacuum at the highest temperature with the vapour pressure of the grease at this highest temperature. E.g., if your vacuum could reach 10-7 Torr and your maximum temperature is 100°C then it is usually advisable to use these values, even if you expect to mostly stay around 60°C. If the vapour pressure is equal to or higher than the vacuum level then the grease will evaporate, causing contamination and leaks.
Please note that temperature vs vapour pressure plots usually use a logarithmic scale due to the extremely high dependence on temperature. Don’t get caught out by only checking against the 20°C vapour pressure!
A more detailed explanation and advice on checking vapour pressure is available by watching our webinar available here: GREASE IS THE WORD!
Once you have identified a grease / greases which can be used at your level of vacuum, move on to checking the working temperature.
Click here to read more about Working Temperature.
To find out more about the Apiezon family of silicone-free high vacuum greases manufactured by M&I Materials Ltd, contact our team of experts available via our helpline: Apiezon Technical Helpline +44 (0)161 864 5409. Alternatively, please Contact Us and will be in touch shortly.