What is rebound resilience?
Rebound elasticity describes how much energy an elastomeric material returns after an impact-like deformation. It therefore shows how „springy“ a rubber is. A high value means that the material largely returns the energy introduced. A low value indicates that it absorbs a large proportion of the impact energy and converts it into heat.
Factors influencing rebound resilience
- Polymer base: Natural rubber has a very high rebound resilience; Silicones or FKM usually show lower values
- Degree of cross-linking: A higher degree of cross-linking increases the rebound resilience up to an optimum, elastomers that are cross-linked too much become rigid, which reduces the rebound resilience
- FillersReinforcing fillers such as carbon black or silica reduce the rebound resilience because they absorb energy and thus dampen it
- HardnessSofter mixtures often have higher rebound properties than harder ones, although this in turn decreases with very soft mixtures as a result of plastic deformation
- Temperature: The rebound resilience decreases at low temperatures and increases again at moderate temperatures. At very high temperatures, it decreases due to increasing viscous damping
- Ageing: With increasing ageing (e.g. due to heat or ozone), the material becomes more brittle and loses its rebound properties
Test for rebound resilience
The most common test method is the rebound test in accordance with DIN 53512 or ISO 4662:
- A defined test specimen (e.g. hemisphere or pendulum) is dropped onto the material from a fixed height
- The height of the rebound is measured
- Result: Rebound elasticity as a percentage of the initial energy/height h_r/h_0 x 100%
- A material with 70% rebound resilience returns 70% of the deformation energy as kinetic energy. The rest is converted into heat, e.g. through internal friction