In the engineering applications of rubber materials, compression set and resilience are core parameters that directly affect their service performance and lifespan. A scientific understanding of the numerical characteristics of these two indicators can help optimize material selection and structural design, thereby enhancing product reliability under complex operating conditions. This article will analyze, from a numerical perspective, the intrinsic relationship between compression set and resilience, and, combined with practical application scenarios, explore how to achieve superior overall performance through material and process control.

I. Numerical Interpretation and Practical Significance of Compressive Permanent Deformation

Compressive permanent deformation is typically expressed as a percentage and reflects the degree of residual deformation remaining in the rubber after the compressive load is removed. The higher this value, the weaker the material's ability to recover, and the more likely it is to accumulate deformation over time under sustained compression, thereby affecting its performance in applications such as sealing or vibration damping. Below are typical ranges for several common rubbers under standard test conditions (e.g., ASTM D395, 25% compression, 72 hours). Actual values may vary depending on temperature, duration, and compression ratio:

Natural rubber (NR): Approximately 10%–25% at room temperature, and up to 30%–50% at high temperatures (70–100°C).

Nitrile rubber (NBR): Approximately 15%–30% at room temperature, 35%–50% at 100°C, and up to 40%–60% at 150°C.

Silicone rubber (VMQ): Approximately 5%–10% at room temperature, and about 15%–30% at 200°C.

Fluororubber (FKM): Approximately 5%–15% at room temperature, and about 20%–40% at 150°C.

Ethylene Propylene Diene Monomer (EPDM) rubber: Approximately 10%–20% at room temperature, and about 20%–30% at 100°C.

Chloroprene rubber (CR): Approximately 15%–25% at room temperature, and about 30%–45% at 100°C.

Polyurethane rubber (PU): Approximately 5%–10% at room temperature, and about 20%–35% at 70–100°C.

Lower compression set means that the material can still recover its original shape relatively well after being subjected to prolonged compression, which helps maintain sealing contact pressure and extend service life—particularly critical in static seals and components that bear long-term pressure.

II. Numerical Characteristics of Resilience and Their Engineering Implications

Elasticity is commonly characterized by the rebound percentage; the higher the value, the faster and more effectively the material can return to its original shape after deformation. High-rebound materials are suitable for applications that require frequent deformation, vibration absorption, or rapid recovery. The typical rebound range for rubber is as follows (based on test methods such as ASTM D2632):

Natural rubber (NR): 60%–80% at room temperature, dropping to 40%–60% at high temperatures.

Nitrile rubber (NBR): Approximately 30%–50% at room temperature, and about 20%–40% at 100°C.

Silicone rubber (VMQ): Approximately 30%–50% at room temperature, and about 20%–40% at 200°C.

Fluororubber (FKM): Approximately 20%–35% at room temperature, with further reduction at higher temperatures.

Ethylene Propylene Diene Monomer (EPDM): Approximately 60%–70% at room temperature, and maintains 40%–50% at 100°C.

Polyurethane rubber (PU): Approximately 40%–60% at room temperature, with a slight decrease at higher temperatures.

Styrene-butadiene rubber (SBR): Approximately 50%–70% at room temperature, and approximately 30%–50% at 70°C.

The degree of elasticity is often correlated with the flexibility of a material’s molecular chains and its cross-linking structure. When selecting materials in practice, it’s essential to take into account specific operating conditions: highly elastic materials are commonly used in applications such as shock absorption and power transmission; while certain chemically resistant or high-temperature-resistant rubbers, though exhibiting lower elasticity, are preferred in harsh environments precisely because of their exceptional stability.

III. The Intrinsic Relationship Between Compression Set and Resilience

Generally exhibits an inverse trend.

Under the same conditions, materials with higher resilience typically exhibit lower compression set. For example, natural rubber at room temperature boasts both high resilience—reaching up to 80%—and low compression set—ranging from 10% to 25%. In contrast, fluororubber has relatively lower resilience, and its compression set is comparatively more pronounced. This difference stems from the fact that molecular chains in highly resilient materials can easily return to their original configuration and are less likely to undergo permanent structural changes.

The combined effect of temperature on both.

Increasing temperature typically intensifies the motion of rubber molecular chain segments, leading to a decrease in resilience and an increase in compression set. Take silicone rubber as an example: when the temperature rises from room temperature to 200°C, its resilience can drop from 50% to about 30%, while its compression set increases from less than 10% to between 15% and 30%. This indicates that in high-temperature applications, it is essential to comprehensively evaluate these two factors and select materials with better stability.

The decisive role of material chemical structure

The molecular backbone and side-chain structure of different rubbers directly influence their elasticity and ability to recover from deformation. For example, although fluororubber has lower elasticity than natural rubber, its outstanding thermal stability and chemical resistance ensure that its compression set remains within an acceptable range even in high-temperature and corrosive environments, making it indispensable in the sealing industry.

IV. Approaches and Practical Recommendations for Performance Optimization

To achieve lower compression set and higher resilience in specific applications, systematic optimization can be carried out from the following aspects:

1. Material formulation design

Select an appropriate rubber base material based on conditions such as operating temperature and medium.

Adjust the crosslink density through the vulcanization system (vulcanizing agent and accelerator) to balance elasticity and permanent deformation.

Use reinforcing fillers (such as carbon black and precipitated silica) in combination to enhance mechanical properties and resilience.

Add antioxidants, antiozonants, and other additives to slow down aging and maintain long-term elasticity.

2. Key points for process control

Precisely control the vulcanization temperature and time to avoid under-vulcanization or over-vulcanization.

For high-performance products, a multi-stage vulcanization process can be employed to gradually establish a stable network structure.

Ensure uniform mixing to avoid local performance variations.

3. Operating Conditions and Structural Design Optimization

Minimize the operating temperature and avoid prolonged static high-pressure compression.

In sealed designs, set the compression ratio reasonably (typically recommended at 20–30%) to avoid excessive deformation.

By designing the geometry to distribute stress, the risk of localized permanent deformation is reduced.

Select a medium-resistant model or adopt protective measures when operating in chemically corrosive environments.

V. Conclusion

Compressive permanent deformation and resilience are interrelated yet distinct indicators in the performance evaluation of rubber materials. Understanding the material behavior logic behind their numerical values can help engineers make scientifically informed trade-offs during design and material selection. In practical engineering applications, there is no such thing as an “absolutely optimal” material; rather, only through systematic optimization of formulation, processing, and design—tailored to specific service conditions—can rubber products achieve the best balance between elastic recovery and dimensional stability, thereby enhancing the overall reliability and service life of equipment.