Material Rebound Resilience Testing: Determination Methods, Standards, and Applications

Material rebound resilience determination measures the percentage of impact energy that an elastomer, foam, or other viscoelastic material returns after deformation, making it a key indicator of elasticity, damping behavior, and product performance. This technical guide explains the measurement principle, applicable international standards such as ISO 4662, ASTM D2632, and ASTM D3574, specimen requirements, test procedures, and typical industrial applications. Whether you are evaluating tire tread compounds, footwear midsoles, sealing elements, or flexible polyurethane foams, understanding rebound rate testing helps you select and verify materials with the right balance of energy return and energy absorption.

Technical Overview

Rebound resilience, commonly referred to as the rebound rate or rebound value, is defined as the ratio of the mechanical energy restored by a material after an impact to the mechanical energy of the impact itself, expressed as a percentage. In practical terms, it quantifies how "lively" a material is: a material with a rebound resilience of 80 percent returns 80 percent of the impact energy it receives, while the remaining 20 percent is dissipated as heat due to internal friction within the polymer network.

For drop-based and ball-rebound methods, the result is calculated from height measurements, because kinetic energy is proportional to height in free fall: R = (h2 / h1) × 100%, where h1 is the drop height and h2 is the maximum rebound height. For pendulum methods, the equivalent energy ratio is derived from the drop angle α and the rebound angle β: R = (1 − cos β) / (1 − cos α) × 100%.

Rebound resilience is fundamentally a manifestation of the viscoelastic character of the material. Materials with a high loss factor (tan δ) dissipate more energy and exhibit low rebound, while highly elastic materials with low hysteresis losses exhibit high rebound. The property is strongly influenced by temperature (rebound decreases sharply as the test temperature approaches the glass transition temperature), impact velocity, strain amplitude, filler loading, crosslink density, plasticizer content, and the degree of aging or fatigue the material has experienced.

The principal standards governing rebound resilience determination include ISO 4662 (rubber, vulcanized or thermoplastic — determination of rebound resilience), ASTM D2632 (rubber property — resilience by vertical rebound), ASTM D3574 Test H (resilience of flexible cellular materials by ball rebound), ISO 8307 (flexible cellular polymeric materials — resilience by ball rebound), GB/T 1681 (determination of rebound resilience of vulcanized rubber in China), and JIS K 6255 (Japanese industrial standard for rubber rebound resilience). Accredited third-party laboratories routinely perform these tests for product development, quality control, and certification support.

Testing Samples

Vulcanized Rubber Compounds

Standard test pieces are usually flat molded pads with smooth, parallel surfaces, free of pores, blisters, and machining damage. Typical pendulum specimens are approximately 12.7 mm thick with a test surface of sufficient area to accommodate the striker; thinner sheets may be stacked only when permitted by the applicable standard. Specimens should be conditioned at 23 ± 2 °C for at least 3 hours before testing, and a minimum resting period after vulcanization (commonly 16 hours) must be observed. Buffed surfaces should be avoided wherever possible because grinding alters the surface structure and affects the result.

Thermoplastic Elastomers and Polyurethanes

Injection-molded or compression-molded plaques of TPU, TPE, SBS/SEBS compounds, and cast polyurethane elastomers can be evaluated using the same pendulum or vertical rebound approaches, provided the specimen thickness and surface condition meet the method requirements. These materials are widely tested for footwear, caster wheels, damping elements, and wear-resistant components.

Flexible Cellular Foams

For flexible polyurethane foams, latex foams, and other cellular materials tested by ball rebound, specimens are typically cut to a minimum thickness of about 50 mm, with flat cut surfaces perpendicular to the direction of ball impact. Molded foam parts may be tested on designated zones, taking care that the measured region is representative of bulk foam properties rather than skin effects.

Finished Products and Components

Cut sections from tire treads, footwear midsoles and outsoles, sports flooring, anti-vibration mounts, conveyor belt cover compounds, rubber balls, sealing profiles, and O-rings can be tested directly when a suitably flat, uniform test area can be prepared. Testing finished goods verifies that formulation, processing, and curing conditions have delivered the intended resilience in the actual product geometry.

Testing Items

Rebound resilience determination can be carried out as a single-point quality measurement or as part of a broader characterization program. Common test items include:

• Rebound resilience at standard laboratory temperature (23 °C)
• Low-temperature rebound resilience at sub-zero temperatures (for example −10 °C, −20 °C, −30 °C, or −40 °C) to assess winter performance of tire compounds and dynamic seals
• Rebound resilience retention after heat aging, oil immersion, ozone exposure, or UV weathering
• Comparative rebound evaluation of competing formulations, filler loadings, or curing systems
• Rebound mapping across product zones, such as tire tread center versus shoulder, or heel versus forefoot regions of footwear midsoles
• Rebound resilience of high-resilience (HR) foam grades for seating and comfort applications
• Batch-to-batch consistency checks for incoming material inspection and outgoing quality control

Testing Methods

Several standardized methods exist, and they are not interchangeable: results from different apparatus types may differ by several percentage points for the same material. The method must therefore always be reported together with the numerical result.

Pendulum Method (ISO 4662 / GB/T 1681 / JIS K 6255)

A pendulum-mounted striker of defined mass and impact energy (0.5 J in the widely used Schob-type configuration) is released so that it strikes the test surface of a rigidly clamped specimen. The pendulum rebounds to a lower maximum angle, and the ratio of the restored energy to the incident energy is computed from the drop and rebound angles. The specimen receives a small number of conditioning impacts before the recorded readings are taken, and the median of at least three valid measurements is reported as the rebound resilience. Pendulum methods are the reference procedures for rubber compounds and are especially suitable for stiffness grades that are too soft for reliable vertical plunger testing.

Vertical Rebound Method — Bashore Resiliometer (ASTM D2632)

A lightweight plunger with a conical tip falls freely under gravity through a guide onto the horizontal surface of a specimen approximately 12.7 mm thick. The rebound height of the plunger is captured by an electronic, optical, or pneumatic sensing system, and the resilience is calculated as the rebound height divided by the drop height, expressed as a percentage. The method is fast, requires only a small specimen, and is widely used for quality control of vulcanized rubber parts and cellular products.

Ball Rebound Method for Foams (ASTM D3574 Test H / ISO 8307)

A calibrated steel ball of approximately 16 g is dropped from a fixed height of 500 mm onto the foam specimen, and the maximum rebound height is measured with a video system or height sensor. The rebound resilience equals the rebound height divided by the drop height, expressed as a percentage. This method is the industry-standard indicator of foam "liveliness" and comfort response: conventional flexible foams typically fall in the range of 35–55 percent, while high-resilience grades reach 60 percent or more.

Instrumented Drop Tower Testing

For research and engineering purposes, an instrumented drop tower or falling-dart rig can measure the incident and reflected energy directly from force–time or velocity–time data. This approach provides richer information, such as energy absorption curves and strain-rate sensitivity, and can correlate rebound behavior with dynamic mechanical analysis (DMA) data.

Reporting of Results

A compliant test report states the standard and method used, specimen description and dimensions, conditioning and test temperature, the number of impacts and readings, the median rebound resilience value, and any deviations from the standard. Testing at non-ambient temperatures must clearly identify the chamber temperature and soak time.

Applications

Rebound resilience data directly influence material selection, product design, and performance claims across many industries:

• Tires: tread compounds with high rebound at elevated temperature exhibit lower hysteresis and reduced rolling resistance, improving fuel economy, while controlled low-temperature rebound relates to wet grip and winter performance.
• Footwear: midsole and outsole rebound correlates with energy return, cushioning responsiveness, and wearer comfort, and is frequently cited in performance marketing claims.
• Sports surfaces and flooring: rebound values characterize ball response, playability, and athlete-surface interaction for running tracks, gym floors, and court surfaces.
• Vibration control: engineers deliberately select low-rebound, high-damping compounds for engine mounts and isolators, and high-rebound compounds for elastic elements that must return energy efficiently.
• Seals and dynamic components: rebound resilience, together with compression set and stress relaxation, indicates the ability of sealing materials to maintain contact under cyclic deformation.
• Foam seating, bedding, and packaging: rebound grades differentiate comfort feel, support, and protective performance of cellular products.
• Quality assurance: routine rebound testing supports formulation screening, incoming inspection, process capability monitoring, and batch release in accredited third-party laboratories and in-house facilities.

FAQ

What exactly does rebound resilience measure?

It measures the percentage of impact energy a material returns after deformation. A value of 70 percent means the material gives back 70 percent of the impact energy and dissipates the remaining 30 percent as heat. It is therefore a direct indicator of elasticity and an inverse indicator of damping.

Which test method should be chosen?

Solid rubber compounds are normally tested by the pendulum method per ISO 4662 or GB/T 1681, or by the Bashore vertical rebound method per ASTM D2632 when fast quality control is needed. Flexible foams are tested by ball rebound per ASTM D3574 Test H or ISO 8307. The choice should follow the applicable product specification or customer requirement.

Are results from different methods comparable?

No. Impact velocity, striker geometry, and specimen configuration differ between methods, so rebound values obtained on different apparatus are not directly interchangeable. Only results generated by the same method and under the same conditions should be compared.

What specimen size and how many samples are required?

Typical requirements are specimens approximately 12.7 mm thick for solid rubber methods and at least about 50 mm thick for foam ball rebound testing. At least three specimens, or three valid measurement positions, are recommended, and the median value is reported.

Can rebound resilience be tested at low temperature?

Yes. Specimens are conditioned in an environmental chamber at the specified sub-zero temperature before impact. Low-temperature rebound is particularly important for winter tire compounds, outdoor seals, and cold-climate elastomeric components, because rebound drops sharply near the glass transition region.

What are typical rebound values for common materials?

Indicative ranges at room temperature include natural rubber compounds at roughly 70–90 percent, SBR compounds around 45–65 percent, butyl rubber as low as 10–25 percent due to its strong damping character, TPU elastomers around 50–70 percent, conventional flexible polyurethane foams around 35–55 percent, and high-resilience foams above 60 percent. Exact values depend on formulation and the test method used.

Is rebound resilience the same as the rebound number measured on concrete?

No. The concrete rebound hammer (for example per ASTM C805 or EN 12504-2) records a rebound index used to estimate surface hardness and uniformity of hardened concrete. Material rebound resilience testing, by contrast, quantifies energy return of elastic and cellular materials using pendulum, plunger, or ball-drop apparatus.

How does rebound resilience relate to damping and product performance?

Rebound resilience and damping are complementary: a material with low rebound dissipates more energy and is preferred for vibration isolation and impact protection, whereas a material with high rebound returns energy and is preferred where responsiveness, efficiency, or energy return matters. Because rebound correlates inversely with the loss factor tan δ, it is often used alongside dynamic mechanical analysis to rank compounds for rolling resistance, grip, and comfort.