Test standards Alpine supports: ASTM D6147, ISO 3384
Compression Stress Relaxation is one of the most valuable tests for understanding long-term sealing performance. It quantifies how a material’s seal force decays over time when compressed and under thermal, chemical, or environmental aging conditions. This test is especially important for applications where elastomers must maintain a reliable seal across extended service life in extreme temperatures or aggressive chemical exposure.
CSR testing mimics real-world conditions by compressing a specimen, such as an O-ring, and measuring how much force it retains over time. As the material relaxes, seal force is lost, and data from this process helps predict whether the material will continue to perform effectively in application. Examples of the testing fixtures can be seen here:
Alpine Polytech performs CSR testing using a wide range of O-ring sizes such as -325 as well as ASTM D395 Type I and II test specimens and offers both vacuum and positive pressure environments to replicate operating conditions. Our team can help interpret CSR data and determine how different aging solutions impact long-term performance. Alpine also offers In-Situ Testing, our patent pending technology that allows for CSR testing while samples are immersed in aging environments. Alpine is the only lab in the industry that offers this service.
Whether you’re qualifying new elastomers, plastics, or composite materials, Alpine Polytech provides precise CSR testing according to internationally recognized standards as well as bespoke methods customized by our clients. Our results help customers assess mechanical integrity across a wide range of service conditions.
Alpine Expanded Capabilities
Test conditions we support:
- In-Situ Testing options available
- Custom specimen preparation
- Instron capabilities up to 135,000 lbs.
- Aging in acids, bases, brines, hydrocarbons, and extreme pressure
- Cryogenic to 400°C aging capabilities
- Seven Instron machines to increase workflow efficiency and cost effectiveness
- Instron coolers and ovens for temperatures from cryogenic to 300°C on the machine
Alpine offers compression stress relaxation (CSR) testing to evaluate long-term sealing force retention of elastomers under relevant service conditions. We provide custom specimen preparation and utilize Instron systems with capacities up to 135,000 lbs., equipped with on-machine coolers and ovens for temperatures up to 300°C. Our aging capabilities from cryogenic to 400°C enable CSR testing after exposure to acids, bases, brines, hydrocarbons, and extreme pressures. In-situ CSR testing options are also available, allowing for real-time measurement of stress relaxation while samples remain under exposure conditions, ensuring accurate, representative data for sealing performance validation and material development
Testing Details
In a CSR test, the specimen is compressed to a specified strain, usually mimicking the squeeze that would be experienced in application. The sample is placed in a precision jig that maintains this compression throughout the test. Fixtures can be configured to support a range of seal forces, typically from 50 to over 250 pounds-force (lbf), and are compatible with both internal vacuum and positive pressure setups. The entire fixture is then aged in a controlled environment, which may include elevated temperatures, corrosive fluids or gases, and pressure, replicating real-world service conditions.
Seal force is measured in four short compression cycles, both before and after aging. The difference in measured force indicates how much the material has relaxed and how its sealing performance has degraded over time. This makes CSR testing critical for evaluating long-term sealing reliability.
Standard methods include ISO 3384 for stress relaxation under compression and ASTM D6147 for O-rings under fluid or aging.