How Do You Evaluate Silicone Parts for Long Term Compression Set Resistance?
Author : HitokaCece HitokaCece | Published On : 21 Oct 2026
Silicone parts are valued for their wide temperature range, flexibility, and resistance to aging. They are used in seals, gaskets, keypads, vibration isolators, and medical components. But silicone is not automatically reliable. A silicone part that is poorly formulated or under cured may take a permanent set and lose its sealing force. In a static seal, this means a leak. In a vibration isolator, it means increased noise and movement. Compression set resistance is therefore one of the most important properties to evaluate.
Silicone Parts Compression Set Test Methods
Compression set is measured by compressing a sample to a fixed percentage of its original height, holding it at a specified temperature for a specified time, then releasing it and measuring how much it fails to recover. The result is expressed as a percentage. A low value means the material recovered well. A high value means it took a permanent set.
The test conditions matter. A test at room temperature may show good results, but the part may be used at high temperature. A test at short duration may not represent months of service. Buyers should ask for compression set data at the actual operating temperature and for a duration that reflects the application. A seal that is expected to last years should be tested for a longer period.
The test method should also be consistent. Different standards use different compression ratios and recovery times. Buyers should confirm which standard was used and compare data on the same basis. A supplier that reports a low compression set without stating the test conditions is not providing useful information.
Silicone Seal Formulation and Curing
Formulation affects compression set. Silicone compounds include fillers, catalysts, and additives. A compound with a high filler content may be harder and more resistant to compression set, but it may also be less flexible. A compound with a low filler content may be softer but may take a set more easily.
Curing is equally important. Silicone can be cured by platinum addition or peroxide. Platinum cured silicone generally has better compression set and lower extractables. Peroxide cured silicone may be cheaper but may have higher compression set. Buyers should ask about the curing system and should request data for the specific compound.
Post curing may also be used. Post curing removes volatile components and improves compression set. A supplier that skips post curing may deliver parts that perform poorly in service. Buyers should confirm the post curing process and the quality records.
Silicone Parts Supplier Documentation and Consistency
Documentation is essential. The supplier should provide the compound specification, the curing system, the compression set data, and the batch records. Buyers should confirm that the data matches the actual production. A supplier that provides data for a different compound is not reliable.
Consistency across batches is the final check. A buyer who approves a sample and then receives parts with different hardness or compression set will face field failures. The supplier should have process controls and should test each batch. Buyers should request samples from multiple production runs and compare them.
Application fit should also be considered. Silicone is not suitable for all environments. It has limited resistance to oils and solvents. A silicone part that performs well in a dry heat application may fail in an oil bath. Buyers should confirm chemical compatibility before selecting silicone.
Conclusion
Evaluating silicone parts for long term compression set resistance requires checking test methods, formulation, curing, documentation, and consistency. The right silicone part maintains its sealing force over time. Buyers should request data at real operating conditions and choose a supplier with controlled processes.
