Prevent O-ring Stiction with Parylene Coatings
If your valves are going to be stored or sitting idle for long periods of time, it’s important to know the rubber o-ring may begin sticking to the plastic o-ring seat or poppet. This natural occurrence is known as stiction, or the friction that tends to prevent stationary surfaces from being set in motion. By applying a parylene coating to the o-rings, they can remain in a passive state longer and prevent the risk of an elevated opening pressure.
About Parylene Coatings
Parylene is used as a protective polymer coating for a variety of applications including plastic and rubber. A parylene coating is not simply created and brushed onto our o-rings; it entails a certain process with temperature requirements and specific machinery. At a molecular level, parylene’s original solid form is converted at about 150°C to dimeric gas. Next, the new parylene vapor form is further broken down at 650°C to become a thin, clear film coating. This coating is applied at room temperature with specialized vacuum deposition equipment that allows control of the coating rate and thickness. The vapor condenses on all surfaces equally and can pass through holes as small as one micrometer, which is particularly beneficial for seeping into the small ridges and gaps naturally found in any type of rubber o-ring. With the entire coating process completed at room temperature, using parylene alleviates any possible temperature stress on o-rings.
Beyond preventing stiction due to its resistance to friction, a parylene coating has many beneficial characteristics to ensure it works well with a wide variety of requirements. For the Medical or Food and Beverage Industries, parylene is FDA approved with a Class VI bio-compatibility rating. It also has military approval with a MIL-I-46058C, Type XY rating. Parylene is an excellent barrier to oxygen, moisture, chemicals, solvents, acids, carbon dioxide, fungus, bacteria, water vapor, and many other elements. Additionally, parylene is light-weight, highly reliable, and has excellent adhesion properties.
All 7+ o-ring materials we offer are available with a parylene coating, upon request. To review our o-ring guide, click here.
As always, the more we know about your device’s requirements – including all conditions our valves will be exposed to – the better we can create a precise flow-control product unique to your application. For questions about applying a parylene coating to o-rings for your next order, please: