Rebound Resilience Elastomers

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Rebound resilience elastomers

General

Elastomeric materials are used as shock and vibration absorbers due to their damping properties. Elastomers in particular, such as natural rubber ( plastics – symbols and abbreviated terms: NR), isobutylene-isoprene rubber ( plastics – symbols and abbreviated terms: IIR), acrylonitrile-butadiene rubber ( plastics – symbols and abbreviated terms: NBR) and styrene-butadiene rubber ( plastics – symbols and abbreviated terms: SBR) are suitable for these applications because they exhibit high damping over a wide temperature range [1].

Definition of rebound resilience

The determination of the rebound resilience (R) according to DIN 53512 [2] or ISO 4662 [3] allows an evaluation of the damping behaviour of elastomeric materials. Here, a pendulum (Schob pendulum) with a working capacity of 0.5 J strikes the surface of a test specimen vertically at a defined velocity. The rebound resilience is defined by the quotient of the rebound height h_R and the height of fall of the pendulum h₀ or by the ratio of the energy gained E_R to the energy expended E_A:

$R={\frac {h_{R}}{h_{0}}}\cdot 100\ \%$

(1)

$R={\frac {E_{R}}{E_{A}}}\ (\%)$

(2)

The following relationship exists between rebound resilience and loss factor tan δ for small values of the loss factor [1]:

$R={\frac {E_{R}}{E_{A}}}=1-\pi \cdot tan\ \delta$

(3)

The higher the value determined for the parameter R, the better the dynamic-mechanical behaviour (see also: Dynamic-mechanical analysis (DMA) – General principles) can be assessed under the test-methodical boundary conditions with regard to the type of stress and test speed.

Application examples

The Figure 1 shows the relationship between rebound resilience and material composition. The carbon black reinforced SBR vulcanisate shows a higher rebound resilience compared to the vulcanisate with an additional standard plasticiser. If, on the other hand, bio-based plasticisers were mixed in, higher values for rebound resilience were determined in some cases compared to the vulcanised material (see also: Vulcanization) without plasticisers. The higher the determined material value, the more elastic the material.

Fig. 1:

Rebound resilience for carbon black reinforced (50 phr) SBR vulcanisates with different plasticisers (15 phr) (own investigations Polymer Service GmbH Merseburg (PSM)))

A direct correlation between the rebound resilience and the SHORE A hardness material values (see Table 1) cannot be established. The highest Shore A hardness value of A 72 was determined for the vulcanisate without plasticiser (SBR/carbon black). However, the highest values for rebound resilience were determined for the vulcanisates with bio-based plasticiser 1, with 54 SHORE A.

Table 1: SHORE A hardness values for carbon black reinforced (50 phr) SBR vulcanisates with different plasticisers (own studies Polymer Service GmbH Merseburg (PSM)))

Vulcanisate	SHORE A (-)
SBR/carbon black	72 ± 0.55
SBR/carbon black with standard plasticiser	60 ± 0.21
SBR/carbon black with bio-based plasticiser 1	54 ± 0.86
SBR/carbon black with bio-based plasticiser 2	55 ± 0.61
SBR/carbon black with bio-based plasticiser 3	56 ± 0.53

The investigations show that elastomers with the same SHORE A hardness values can have very different rebound resilience. Finally, the rebound resilience enables a statement to be made about the hysteresis behaviour (see also: compression hardness) under impact stress, which describes the purely elastic behaviour of a material.

Correlation of rebound resilience with SHORE A hardness

From the application example, it becomes clear that it is difficult to conclude the rebound resilience from the SHORE A hardness, which is relatively easy to determine experimentally. Rebound resilience is a structure-sensitive material parameter that depends on the elastomer type, the material formulation (with plasticiser) and the test temperature.

See also

• Vulcanization
• Elasticity
• Ductility plastics
• SHORE Hardness

References

[1]	Röthemeyer, F., Sommer, F.: Kautschuk Technologie. Carl Hanser Munich, 2nd revised edition (2006), (ISBN 978-3-446-40480-9)
[2]	DIN 53512 (2000-04): Testing of Rubber – Determination of Rebound Resilience (Schob Pendulum)
[3]	ISO 4662 (2017-06): Rubber, Vulcanized or Thermoplastic Elastomers – Determination of Rebound Resilience
[4]	Schnetger, J.: Lexikon Kautschuktechnik. Hüthig, 3rd completely revised and expanded edition (2004), (ISBN 978-3-7785-3022-1; see AMK-Library under K 7)