O-rings, gaskets and seals are widely used in vacuum systems for sealing purpose. This article introduces some mostly used rubber vacuum sealing materials.
1. Natural Rubber
Natural rubber is commonly used as a vacuum sealing material in rough vacuum or low vacuum systems. The material has high air permeability and poor oil and ageing resistance. It is not resistant to high temperature as well, so it’s generally used below 100°C.
2. Butyl Rubber
Butyl rubber has lower permeability than that of natural rubber. This rubber can be used as vacuum sealing material for vacuum requirement not more than 10-5 Pa (10-7 mbar). In case this rubber material is used in higher vacuum, it may result in loss of quality due to sublimation.
3. Nitrile Rubber
Nitrile rubber, or NBR (Nitrile Butadiene Rubber), is a balanced synthetic rubber with good resistance to oil, heat and water and low permeability. This material can be modified by adding other materials. It’s applicable for high vacuum sealing at working temperatures below 150°C.
4. Polyurethane Rubber
Polyurethane rubber has excellent mechanical and tearing strength. The material is oil, abrasion, radiation and impact resistant, but it’s not resistant to high temperature, water, acid and alkali. Therefore, it’s suitable for vacuum applications with low speed and good heat dissipation. This rubber is typically used in vacuum equipment, vacuum valves and low-speed transmission vacuum components.
5. Fluoro Rubber
Fluoro Rubber, also known as FKM (Fluorine Kautschuk Material), has low permeability, more or less the same as that of butyl rubber. This rubber can be used as a vacuum sealing material for high vacuum and ultra-high vacuum systems (10-5 to 10-7 Pa). It’s resistant to high temperature and various media, and it works stably in sunlight, ozone and ambient atmosphere. One significant shortage of this material is the high cost.
6. Silicone Rubber
Silicone rubber features high heat resistance and it’s the best among all above-mentioned rubber vacuum sealing materials for high temperature applications. This material can be used under 200°C for very long time and the working temperature range is -100 to 350°C. However, this rubber has also very high permeability, ten to tens of times as that of ordinary rubber, with high coefficient of linear expansion.
Remarkbl uses mostly FKM gaskets and O-rings inside the vacuum pumps to ensure high reliable sealing quality.