A Guide to Compression Force Deflection: Concepts, Measurement, and Applications

1. What is Compression Force Deflection (CFD)?

Compression Force Deflection (CFD), also referred to as compression stress or compression force, describes the stress generated when a silicone foam material attempts to return to its original shape after being compressed. It reflects the material's ability to provide a rebound force when compressed. This rebound ability is due to the cross-linked polymer structure of silicone rubber, which stores and releases elastic energy.

2. Why is Compression Force Deflection Important?

In sealing and cushioning applications, CFD is a crucial performance metric in sealing and cushioning applications, highlighted by:

• Long-term sealing performance: High CFD ensures that the material can maintain tight contact with sealing surfaces (e.g., waterproofing of electronic devices or hood seals in vehicles) even after prolonged compression, preventing leakage.
• Dynamic compensation: When vibration or temperature changes cause dimensional fluctuations, silicone foam can continuously rebound to compensate for gaps, helping maintain the integrity of the seal.

3. How is Compression Force Deflection Measured?

CFD is typically measured per ASTM D1056, using the force required to compress the material to 25% of its original thickness as the standard reference point.

When selecting the appropriate CFD, the following factors should be considered:

• Too little compression may lead to poor contact due to thickness tolerances or stress relaxation. Meanwhile, excessive compression (over 50%) may cause cell structure damage and shorten material life.
• The size of the gasket and the roughness of the contact surface.
• The sealing medium (air, water, or other chemicals) may also affect material selection.

4. What Does the Stress-Strain Curve Show? (Taking Futureway® Silicone Foam as an Example)

The stress-strain curve is a key tool for understanding the mechanical behavior of silicone foam and is typically divided into three stages:

• Elastic region: Stress increases proportionally with strain. The slope of the curve represents the elastic modulus and determines cushioning performance under low loads.
• Plateau region: Stress increases slowly over a longer range, indicating gradual collapse of the foam structure. This stage offers the highest energy absorption efficiency.
• Densification region: Stress rises sharply after a certain point, as the cells have fully collapsed and the material behaves more like a solid rubber. Entry into this region should be avoided to prevent permanent damage.

5. How to Select the Right CFD for Your Application

• Higher CFD materials: Firmer, ideal for structural or mechanical cushioning.
• Lower CFD materials: Softer and conformable, suitable for sealing and gap-filling.

6. Summary

Compression Force Deflection is a critical parameter for the success of silicone foam in sealing and cushioning applications. Through standardized testing and stress-strain curve analysis, engineers can accurately match material performance with application needs, improving product reliability and stability.