Relationship between Hardness and Elasticity of Rubber

I. Definitions of Hardness and Elasticity:

Hardness refers to the surface resistance to indentation of an object, usually measured using hardness testers such as Shore A, Shore D, or IRHD. Elasticity is the ability of an object to regain its original shape after deformation, indicating its ability to return to its initial state after being subjected to force.

II. Relationship between Rubber Hardness and Elasticity:

In general, there is a negative correlation between rubber hardness and elasticity. This means that as rubber hardness increases, elasticity decreases. This is because higher hardness makes rubber materials more resistant to deformation and, consequently, less able to recover their original shape. Conversely, lower rubber hardness is associated with higher elasticity, as softer materials deform more easily and recover their original shape more readily.

III. Factors Influencing Rubber Hardness and Elasticity:

1. Material Composition: Different rubber materials have varying compositions, leading to differences in hardness and elasticity.

2. Crosslinking Density: Higher crosslinking density results in higher rubber hardness and lower elasticity.

3. Type and Amount of Hardening Agent: Different hardening agents influence rubber hardness and elasticity differently.

IV. How to Choose Rubber Material According to Specific Needs:

For general applications, rubber materials with Shore A hardness between 40 and 80 are commonly chosen. Such materials strike a balance between moderate hardness and good elasticity, meeting common usage requirements.

If exceptionally high elasticity and low hardness are required, materials with Shore A hardness below 20 are preferred. Conversely, if high hardness and relatively lower elasticity are needed, materials with Shore D hardness above 70 should be selected.

In summary, choosing the right rubber material involves considering both hardness and elasticity, as well as specific application conditions such as temperature and pressure.