ISO 2285 Rubber, Vulcanized or Thermoplastic - Tension Set, Elongation and Creep Tests under Constant Tensile and Constant Extension Loads

The standard “ISO 2285 Rubber, vulcanized or thermoplastic - Determination of tension set under constant extension and of tension set, elongation and creep under constant tensile load” developed by the International Organization for Standardization (ISO) describes a number of methods for determining dimensional changes in vulcanized or thermoplastic rubber test pieces during and after tensile loading for relatively short periods at constant extension or under constant loading.

The retained elongation test is intended to measure the ability of rubbers to retain their elastic properties after being extended to a specified stress at a standard laboratory temperature, maintained for a specified time at the same or a specified higher temperature and then released at the test temperature or standard laboratory temperature.

The constant load test describes a method for determining the elongation, creep and stress set of rubbers subjected to a constant load at standard laboratory temperature.

These test methods are intended to measure the elastic properties of rubber in the hardness range of 20 IRHD to 94 IRHD. Creep measurement is not intended for product design or the evaluation of low-creep materials. ISO 8013 applies to these, and there is no agreement between the results of this test and the test results of ISO 8013.

The constant load test is primarily designed for measuring the state of cure and quality control of thin-walled products. An increase in the state of cure or degree of crosslinking is generally reflected in a decrease in set, creep, or elongation.

For the purposes of this standard, the following definitions apply in addition to the terms and definitions given in ISO 8013:

Constant load set stress refers to the elongation remaining in an unloaded test piece after it has been subjected to a constant load for a specified time. It is expressed as a percentage of the original unloaded length.
Set stress at constant extension refers to the elongation remaining in a test piece in a relaxed state after being subjected to a constant elongation for a specified time. It is expressed as a percentage of the elongation.
Creep is the increase in elongation of a test piece at constant load over a specified period of time. It is expressed as a percentage of the elongation at the beginning of that period.

Test pieces shall be prepared in accordance with ISO 23529. Test pieces shall be cut from flat sheet metal, 2 mm plus or minus 0,2 mm thick, prepared by moulding or by cutting and polishing in accordance with ISO 23529 (except for large ring test pieces, which shall be cut from sheet metal, 4 mm plus or minus 0,2 mm thick). Strip test pieces and flared-end strip test pieces shall be cut using a sharp die with a cutter specified in ISO 23529. Ring test pieces shall be cut from sheet metal by a pair of concentric circular dies or by rotating cutters. The separation of the two cutting edges shall not differ by more than 0,05 mm from the mean value.

For testing under constant strain, strip test pieces should be between 2 mm and 10 mm wide. A width of 6 mm is preferred. The length of a specific strip depends on the selected reference length and the type of tensioning device. Strip test pieces with flared ends should have a narrow length section between 25 mm and 50 mm to serve as the reference length, as shown in the figure. Ring test pieces should be one of the following sizes:

Large ring test piece: thickness 4 mm plus/minus 0,2 mm, outer diameter 52,6 mm plus/minus 0,2 mm, inner diameter 44,6 mm plus/minus 0,2 mm
Small ring test piece: thickness 2mm plus/minus 0,2mm, outer diameter 33,5mm plus/minus 0,2mm, inner diameter 29,5mm plus/minus 0,2mm

For testing under constant load, test pieces must have the shape and dimensions shown in the figure.

Reference marks should be drawn on the test pieces using an ink that does not affect the material and is resistant to the test temperature and a suitable marker.

The ISO 2285 standard is important for the following reasons:

Evaluates long-term elastic behavior: This standard helps determine stress set, elongation, and creep—key properties for evaluating how rubber materials behave under long-term tensile stress. This is critical for understanding how rubber components will perform in real-world applications such as seals, belts, hoses, and suspension systems.
Ensures material suitability: This standard verifies whether a rubber material maintains its elasticity and shape over time by simulating constant tensile loading or elongation. This is important in industries where consistent mechanical performance is crucial (e.g., automotive, aerospace, industrial machinery).
Provides standardized test methods: This standard ensures repeatable and comparable test results across laboratories and manufacturers. This helps with quality control, material comparison, and product certification and compliance.
Supports research and development and materials selection: Designers and researchers use this standard to: select the right rubber compounds for specific loads and applications, improve formulations for better durability, and benchmark new materials against established standards.
Improves safety and reliability: Failures in rubber parts due to creep or permanent deformation can lead to system failures. This standard helps prevent such problems by ensuring that materials meet durability expectations under sustained loads.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, boasts a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the ISO 2285 standard for rubber, vulcanized or thermoplastic - Determination of stress set under constant extension and stress set, elongation, and creep under constant tensile load.