Rebound Rate Testing Process: Standards, Methods, and Technical Guidelines

Rebound rate testing (rebound resilience testing) quantifies the ability of elastic materials such as polyurethane foam, rubber, and sports surfaces to return impact energy after deformation. This guide explains the complete rebound rate testing process, covering applicable standards such as ISO 4662, ISO 8307, ASTM D3574, GB/T 6670, and GB/T 1681, as well as sample requirements, test procedures, calculations, and reporting. Whether you are a manufacturer, importer, or quality engineer, understanding this process helps ensure product compliance and consistent material performance.

Technical Overview

Rebound rate, also known as rebound resilience, is the percentage of impact energy that a material returns after being struck by a falling mass or a pendulum striker. In practice, it is determined by dropping a standard ball or swinging a pendulum onto a conditioned specimen and comparing the rebound height (or rebound angle) with the initial drop height (or swing angle). A higher rebound rate indicates greater elasticity and energy return, while a lower value indicates stronger damping and energy absorption.

Rebound rate testing is widely applied to flexible cellular materials, vulcanized and thermoplastic rubber, footwear midsoles, seating cushions, mattresses, and sports surfaces. The principal international and national standards include ISO 4662 (pendulum method for rubber), ISO 8307 and ASTM D3574 Test H (ball rebound for flexible cellular materials), GB/T 6670 (ball rebound for polymeric foams), and GB/T 1681 (pendulum method for rubber). Testing is typically carried out by accredited third-party laboratories or in-house quality departments using calibrated rebound testers equipped with optical or electromagnetic height sensors.

Testing Samples

Flexible Cellular Foam Materials

Slabstock and molded polyurethane foams, polyethylene foams, and latex foams are submitted as sheets or cut blocks. Specimens are commonly prepared with a minimum thickness of 50 mm; thinner materials may be stacked to reach the required thickness, provided the layers are aligned and adhesive is not used unless permitted by the specification. Test surfaces must be flat, parallel, and free of skin damage, voids, or visible defects.

Rubber and Thermoplastic Elastomers

Vulcanized rubber compounds and thermoplastic elastomers are tested as standard plaques or cylindrical buttons with the thickness defined by the applicable pendulum standard (commonly around 12.5 mm). Specimens must be properly cured, fully conditioned, and representative of production batches.

Footwear and Sports Surface Materials

Midsole compounds such as EVA and PU, insoles, sports floorings, gym mats, and playground safety surfaces can be evaluated using ball rebound procedures adapted to the relevant product specification.

Finished Products and Components

Complete cushions, mattress cores, gaskets, sealing profiles, and balls may be tested directly when the selected standard and the client specification permit testing on finished items.

Testing Items

Depending on the material and specification, a rebound rate test report may include the following items:

• Ball rebound resilience at standard laboratory conditions (23 °C ± 2 °C, 50 % ± 5 % relative humidity)
• Pendulum rebound resilience for rubber materials in accordance with ISO 4662 or GB/T 1681
• Vertical ball rebound of sports surfaces in accordance with EN 12235 where applicable
• Rebound rate retention after heat aging, humid aging, or fatigue conditioning
• Low-temperature or high-temperature rebound performance where required by the product standard
• Comparison of measured values with specification limits and a clear conformity conclusion

Testing Methods

Sample Preparation and Conditioning

Specimens are cut to the dimensions required by the selected standard, and their thickness, mass, and surface condition are recorded. Unless otherwise specified, samples are conditioned in a standard laboratory atmosphere (23 °C ± 2 °C and 50 % ± 5 % relative humidity) for at least 16 hours for rubber and typically 12 to 24 hours for foam materials before testing. Products compressed during transport should be allowed to recover for the recovery period defined by the specification.

Ball Rebound Method

The apparatus consists of a vertical guide tube, a calibrated steel ball of approximately 16 g, a release mechanism set to a standard drop height (typically 500 mm), and a height-measuring system based on optical, acoustic, or electromagnetic sensors. The specimen is placed on a rigid, level base with the test face horizontal. The ball is released onto the specimen, and the maximum rebound height is recorded. A series of impacts, commonly three to five at each of several positions across the specimen face, is performed while respecting the minimum edge distance stated in the standard. The rebound rate is calculated as the ratio of rebound height to drop height multiplied by 100 %.

Pendulum Rebound Method

For dense rubber materials, a pendulum tester is used. The specimen is clamped against a rigid anvil, and a pendulum striker of specified mass and geometry is released from a defined angle to strike the specimen. The rebound angle or rebound height of the pendulum is measured, and rebound resilience is expressed as the percentage of impact energy returned by the material. The instrument must be leveled and zeroed before each session, and the friction losses of the pendulum must be verified within the tolerance stated by the standard.

Data Processing and Reporting

• Individual rebound values and the arithmetic mean are calculated, with anomalous readings handled according to the rules of the standard
• The final result is rounded to the nearest 1 % unless otherwise specified
• The test report identifies the standard applied, apparatus type, specimen dimensions and orientation, conditioning history, test temperature, individual and mean results, and any deviations from the procedure
• Instrument calibration status and reference checks are documented to support the traceability of results

Applications

Rebound rate testing supports material development, production control, and compliance verification across many industries:

• Quality control of high-resilience polyurethane foam for mattresses, pillows, and automotive seating
• Evaluation of footwear midsole elasticity, cushioning durability, and energy return
• Verification of sports surfaces, gym mats, and playground safety surfacing prior to installation acceptance
• Assessment of rubber compounds for seals, vibration isolators, tires, and industrial components
• Comparison of incoming raw material batches and supplier qualification programs
• Technical support for product certification, tender documentation, and failure analysis investigations

FAQ

What is the difference between rebound rate and rebound resilience?

The terms are largely interchangeable: both express, as a percentage, how much impact energy a material returns. Ball rebound methods derive the value from rebound height, while pendulum methods derive it from rebound angle or rebound energy.

Which standard should be selected for foam versus rubber?

Flexible foams are usually tested to ASTM D3574 Test H, ISO 8307, or GB/T 6670 using the ball drop method. Vulcanized and thermoplastic rubber is generally tested to ISO 4662 or GB/T 1681 using a pendulum apparatus. The final choice depends on the product specification and the target market.

How is rebound rate calculated?

Rebound rate (%) equals the rebound height divided by the drop height multiplied by 100. For pendulum testers, the equivalent calculation uses the ratio of rebound energy, or the rebound height derived from the swing angle, to the initial impact energy.

What are typical acceptance thresholds?

Requirements are defined by the product standard or the contract between supplier and buyer. As a common industry reference, high-resilience flexible polyurethane foam is often expected to achieve a ball rebound value above 45 %, while conventional foams typically fall between 30 % and 45 %. Exact limits should always be confirmed against the applicable specification.

Is rebound rate testing the same as the rebound hammer test used on concrete?

No. The concrete rebound hammer method described in EN 12504-2 measures a rebound number used to estimate the compressive strength of hardened concrete in structures. Rebound rate testing, by contrast, measures the energy return of elastic materials such as foams and rubbers.

How long does a standard rebound rate test take?

Once specimens are conditioned, the measurement itself takes only minutes per sample. Considering conditioning time, instrument calibration, and report preparation, accredited third-party laboratories commonly issue results within three to seven working days.