Measurement Protocol
Global testing standard used to determine the compression set of vulcanized or thermoplastic rubber. Evaluation under iso 815 provides a quantitative value for the permanent deformation remaining after a specimen has been compressed and then allowed to recover. This value is expressed as a percentage of the initial compression.
It is a fundamental metric for assessing the sealing capability of a material over time.
Apparatus Specification
Precision spacers are used to maintain a constant deflection of the rubber sample between two parallel steel plates. Surfaces of the plates must be polished to a specific roughness to prevent friction from affecting the results.
Temperature Influence
Testing occurs at ambient, elevated or low temperatures to match the expected service environment. Higher temperatures generally increase the compression set as they accelerate the chemical changes and molecular sliding within the polymer. Standardized durations for the test range from twenty four hours to several weeks depending on the material and application.
Data Interpretation
Final thickness is recorded after the sample has been removed from the plates and allowed to rest for a specific period, usually thirty minutes. Variations in this rest time can lead to inconsistent readings as the material continues its elastic recovery. Precise micrometer readings are required to ensure the accuracy of the final percentage.
The result indicates whether a gasket will stay energized against a mating surface or leave a gap that allows leakage.
