Weather is hard on gasket material, thus identifying a weather resistant gasket material is important. Ultraviolet (UV) rays in sunlight attack bonds between carbon atoms in many rubbers. Ozone, (O3) often found in polluted industrial areas and around electrical enclosures, does the same. Temperature extremes, especially cold, affect material performance, as can moisture.
Open vs Closed-Cell Gasket Material
Open cells will absorb moisture. If temperatures drop to freezing the subsequent expansion could quickly destroy the material. Always choose closed cell material for a gasket that’s likely to get wet.
Materials to Avoid in Outdoor Applications
Inexpensive nitrile rubber/NBR, often selected for its good oil and solvent resistance, is not a good choice for weather resistant gasket material. The same goes for SBR. Nitrile gasket material is poor with both O3 and UV light, although water resistance is quite good. Its low-temperature limit is around -30F (-34C).
Better Weather Resistant Gasket Materials
Neoprene is a popular choice for gasket material but is not recommended for outdoor use. While it can handle a wide temperature range and offers moderate weather resistance, O3 resistance is poor.
Best Weather Resistant Gasket Materials
A little more expensive than Neoprene, EPDM is good for outdoor gasket applications not involving exposure to oils or solvents. EPDM provides a combination of good O3, UV, and general weather resistance.
Like EPDM, silicone gasket material resists attack by O3, UV, and general weather resistance, but also has excellent fungal and biological resistance. (Sometimes relevant in humid climates.) It has a wide temperature range but poor abrasion resistance is a limitation in applications with a significant joint movement or frequent opening. Silicone also suffers from high gas permeability and is not recommended for use with ketones, petroleum or chlorinated solvents.
For superior outdoor performance, fluorosilicone materials stand out. These have excellent resistance to O3, UV, and weather plus a very wide temperature range. They are also good with fuels. Their main limitations are poor abrasive performance and high price.
Gasket Material Selection Advice
Always consider the application environment when choosing weather resistant gasket material. Outdoor locations expose a gasket to UV light, weathering, and possibly O3. Extremely low temperatures can also be a problem. Hennig Gasket material specialists can provide further advice.