Deciphering compression set: a key indicator that affects sealing performance
In industrial applications, the performance of rubber seals directly determines the sealing effect and service life of equipment. As one of the core indicators, the Compression Set not only reflects the elastic recovery ability of the material but also directly affects the reliability of the seal after long-term compression. This article will analyze this key indicator in depth from the perspectives of scientific principles, influencing factors and optimization strategies, help users choose high-performance seals, and provide technical reference for the industry.
Compression set: definition and importance
Compression set refers to the amount of residual deformation (usually expressed as a percentage) in which a rubber material cannot fully regain its original shape after being compressed for a certain amount of time, temperature, and pressure. The higher the value, the worse the elastic recovery ability of the material after long-term pressure, which may lead to seal failure, leakage, and other problems.
For example, the compression set of natural rubber (NR) is 10%-25% at room temperature, but may rise to 30%-50% at high temperatures (70-100°C); Silicone rubber (VMQ), on the other hand, retains a low deformation rate of 15%-30% at high temperatures (200°C), making it suitable for extreme environmental applications.
Five key factors affect the compression set
Material type and chemical structure
The molecular chain structure of different rubber substrates directly affects their resilience:
Natural Rubber (NR): High elasticity but poor aging resistance, suitable for room temperature environment.
Fluoroelastomer (FKM): High temperature and chemical resistance, but low resilience (20%-35% at room temperature).
Silicone rubber (VMQ): excellent high-temperature stability, deformation rate of only 15%-30% at 200°C, suitable for aerospace seals.
Vulcanization process and crosslinking density
The degree of vulcanization and the type of cross-linked bond significantly affect the material properties:
High cross-linking densities (e.g., peroxide vulcanization systems) reduce chain slip and reduce deformation rates (experiments have shown a reduction of about 20%).
The compression set of the polysulfide bond structure is higher than that of the carbon-carbon bond, and the vulcanization system needs to be selected according to the application scenario.
Filler and formula design
Filler type: Needle or spindle fillers (e.g., magnesium carbonate) are more beneficial than spherical carbon black to reduce distortion.
Glue content: Formulations with low glue content (<30%) usually have less deformation due to more fillers and compact structure.
Environmental conditions
High temperatures, chemical media, and constant pressure can exacerbate permanent deformation:
Increased temperature increases the motility of the molecular chains, resulting in a decrease in resilience (e.g., nitrile rubber can be deformed by up to 60% at 150°C).
Chemical corrosion: Oils or acid-alkali media may cause swelling or embrittlement, so chemical-resistant materials such as fluoroelastomers should be selected.
Aging and fatigue
Ultraviolet light, ozone, and oxidation reactions can disrupt molecular chains and accelerate permanent deformation. Adding antioxidants and UV stabilizers improves aging resistance and reduces the deformation rate by about 5%.
Optimization strategy: How to reduce compression set
Material selection and formulation optimization
High-temperature scenario: Silicone rubber or fluoroelastomer is preferred.
Chemical resistance: Nitrile rubber (NBR) or hydrogenated nitrile rubber (HNBR) is more suitable for oily media.
Filler ratio: control the amount of carbon black to avoid overfilling and reducing elasticity.
Process improvement
Multi-stage vulcanization process: Precise control of vulcanization temperature and time to balance crosslinking density and elasticity.
Post-vulcanization treatment: secondary vulcanization eliminates residual stress and improves stability.
Design fit
Compression control: When designing seals, it is recommended to control the compression ratio at 15%-25% to avoid excessive deformation.
Optimization of support structure: add stiffeners or composite layer structure to disperse local pressure.
Conclusion: Choose a professional to ensure long-lasting sealing
The compression set is the core index used to measure the performance of rubber seals, which needs to be comprehensively optimized from multiple dimensions of material, process, and design. Through scientific selection and customized solutions, the durability and reliability of seals can be significantly improved, and equipment maintenance costs can be reduced.
Contact us today to find out more about the high-performance seals for your application or to learn more about the technical details!
