Where a gasket will be located and used is a key factor for material selection
A key factor to consider when choosing a gasket or seal is to determine where the gasket will be used. Where a gasket or seal will be located determines how exposed it will be to the elements and the effects of weathering. Where weathering is a key consideration, choosing the right material can have a profound effect on seal performance and longevity.
There are four primary factors to consider when choosing gaskets that are resistant to the effects of weathering. They are the following:
Direct sunlight. Exposure to direct sunlight can cause thermal cycling within a gasket or seal. Sunlight exposure can raise the internal temperature of a gasket or seal, and the temperature variation over the cycle can be extreme, especially in colder climates. Thermal cycling can degrade sealing performance significantly – at the coldest point of the cycle, the gasket material may stiffen, crack or break, while at the highest point of the cycle, the material may soften and flex unduly. Thermal cycling can also affect the compression set performance of many gaskets and seals.
Ultraviolet (UV) light. UV light is an invisible component of direct sunlight. Gaskets and seals that are exposed to UV light can undergo premature ageing with a resulting deterioration in material integrity.
Ozone. Exposure to ozone can form cracks in many types of elastomers. Cracking due to ozone exposure may cause premature failure of a gasket or seal.
Oxidation. Oxidation of a rubber compound can occur over time as the material is exposed to atmospheric oxygen. Oxidation can cause molecular chain cleavage in some compounds, where the molecular network of the material is loosened, leading to degradation and softening. Oxidation can also cause cross-linking in some rubber compounds, causing hardening and embrittlement of the compound.
For applications where gaskets and seals are used in and around electrical enclosures and the like, it is vital to choose materials that are resistant to UV light and ozone. In applications where maintaining compression set integrity is paramount, always select materials that will maintain their compression set even when affected by harsh environmental conditions.
Preferred materials
The following rubber materials exhibit good resistance to the effects of weathering and are a good choice for gaskets and seals that will be exposed to the elements:
Silicone rubber. Silicone rubber exhibits excellent elastomeric properties over a wide range of temperatures. The material is also highly resistant to the effects of UV light, ozone and oxygen.
EPDM rubber. EPDM is a synthetic rubber that offers excellent resistance to the effects of weathering and attack by ozone and oxygen. EPDM has a wide range of serviceable temperatures and has very good resistance to many chemicals, oils and acids.
Fluoroelastomer (FKM rubber, or Viton®**).** A fluorocarbon-based rubber which is extremely resistant to weathering and extreme environmental conditions. This material can service high temperatures in continuous service and is also impervious to attack by ozone and oxygen.
At Canada Rubber Group Inc. (CRGI), we have long experience in helping customers to select the optimal material to counter degradation due to weathering and exposure to the elements. Whether the application is general industrial use or automotive, our sales representatives will be pleased to help you select the preferred material for your application. Please contact our sales department at crg@canadarubbergroup.com for further information.