Selecting the best seal for an application involves answering many questions. Temperature and other environmental factors can affect the long-term physical properties of a compound. Therefore, unless a particular application already exists, information on which to base a decision can sometimes be a difficult process.
The best place to begin a search is with existing information. Look for a material with a solid balance of the properties desired for the application. Information about the original material and service conditions can be of help when seeking a replacement material for an existing product. For new products, similar applications can provide valuable information.
The first seal or gasket design consideration is to determine whether an application calls for a sponge or a solid material. Along with this initial determination, closing force requirement needs to be considered.
The primary difference between sponge and dense from the design standpoint is, by example:
1. If the application requires a very low closing force, such as a door seal on a consumer-type product, then a sponge cross-section is most likely best suited.
2. If the application requires a great deal of interference between the two surfaces, such as the bolting together of two components in an industrial setting, then a dense section is the preferred choice.
In either instance, material selection depends upon the physical characteristics and attributes needed in the application.
A second consideration in the materials selection process is the sealing environment.
1. Will there be heat or cold present?
2. Are there solvents or other chemicals present?
3. Is it a static or dynamic sealing application?
4. Will the material be required to stand up against UV and ozone exposure?
Once these questions are answered, it becomes easier to match the right material to the application.
A third consideration is exactly how the seal or gasket will be attached.
1. Is a particular part to be attached by compression fit into a channel?
2. Will an adhesive be applied to the seal?
3. Will there be some sort of mechanical attachment (staples, nails, clips)?
It's important to know which physical, mechanical and chemical resistance properties are required.
-Compression Set at room and operating temperatures
-Aging in sunlight, ozone, heat, storage, etc.
-Speed of recovery from deflection
-Permeability to gasses
-Reaction to acids
-Flame or Temperature extremes
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