When any elastic material is exposed to an impact load, it will initially deform before bouncing back to its original shape. When this occurs, part of the initial energy delivered by the impact is returned as mechanical energy, and a certain portion is dissipated as heat. From this, the rebound resilience is defined as the ratio of mechanical energy returned to the initial mechanical energy exerted from the impact. Higher rebound resilience indicates stronger elasticity, resistance to deformation and a stronger capacity to bear impact loads. However, for some applications such as vibration dampening, lower rebound resilience may be more beneficial.
Testing for this property is typically performed by dropping a standardized pendulum at a set height and speed onto a material sample, as described by standards including ISO 4662 and DIN 53512. After the pendulum impacts the rubber, the rubber will deform before pushing back against the pendulum, returning mechanical energy. Here, the rebound resilience can be quantified by the ratio of the pendulum rebound height to the initial release height.
Compared to other elastomers silicone rubber exhibits intermediate rebound resilience values, typically between 30 and 70 %. Typically this is better than some elastomer families such as butyl or styrene-butadiene rubber, but worse than elastomers such as natural rubber or polyurethane. Notably, silicone rubber can be produced to have high rebound resilience in a range of hardness values. Thus, depending on the application, silicone rubber can be an excellent choice for dampening applications or dynamic applications where higher rebound resilience is more important.
While rebound resilience is one method of quantifying material elasticity, another complementary parameter that characterizes a material elasticity is the material’s compression set. This property describes how readily the shape of a material is permanently affected when subject to prolonged deformation. More information on silicone’s outstanding compression set is available on our articles page.