What Is Elongation?
Elongation at break test is a measurement in which the increase in the measurement length of the sample at the moment of breaking during the tensile test is determined as a percentage as the ratio of the initial dimension length.
Purpose of Elongation
The goal is to determine the elastic capacity of the elastomer and monitor its loss after aging or chemical exposure.
Which Products Is Elongation Applied To?
- Gaskets and sealing elements
- Elastomer profiller
- Hoses and bellows
- rubber coatings
In Which Sectors Is Elongation Used?
Standards Related to Elongation
- ISO 37
- ASTM D412
- ISO 23529
Elongation Conditions
- Measurement
- Measurement length with extensometer; gauge length is used instead of jaw separation
- Tensile speed
- Defined in standard
- Conditioning
- according to ISO 23529
- Reporting
- In percentage; median or mean
Equipment for Elongation
- Calibrated tensile testing machine
- Optical or contact extensometer
- sample cutting die
- Conditioning room
Sample Requirements for Elongation
- Sample edges must be flawless
- Size markings must be clear
- The sliding jaw must hold the sample without nicking it
- The number of specimens is defined in the standard
Duration of Elongation
Typically 2–4 days including conditioning.
Elongation Procedure
- 1Samples are cut, marked and conditioned.
- 2The extensometer is fitted.
- 3Pulling is applied at a defined speed.
- 4The elongation at break is recorded.
- 5Percentage elongation is calculated and reported.
Elongation Acceptance Criteria
The acceptance criterion is the minimum breaking elongation value given in the specification.
Evaluation of Results
The elongation calculated from jaw separation differs from the actual elongation due to jaw displacement; It requires measurement based on standard size. Loss of elongation after aging is one of the most sensitive indicators of rubber degradation.
Elongation Report
- Standard applied
- Measurement method (extensometer)
- Conditioning and speed
- Elongation at break values
- Fracture location
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Material and product specifications
Rubber Testing — What Does This Testing Field Cover?
The section below describes the field that the Elongation test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Rubber testing determines the mechanical behaviour of an elastomer and its resistance to environmental effects. Elastomers are assessed with a different logic from metals and plastics: the real question is not strength but ELASTIC RECOVERY and ageing behaviour.
The function of an elastomer is usually to deform and return: a gasket is compressed and provides a seal, a mount absorbs vibration, a hose expands under pressure. What is measured in the field is therefore not "how many newtons does it withstand" but "how far does it recover after deformation, and how long does it keep doing so".
COMPRESSION SET is therefore the most decisive measurement in the field. If a gasket cannot recover after being held compressed for a long period, it has lost its sealing function even though it has not torn at all. This measurement is made together with temperature, because permanent set increases rapidly with temperature.
Hardness is the most common measurement in the field, using the Shore A and IRHD scales. It is fast and practical but does not define the material on its own: two different compounds of the same hardness can show completely different ageing and fluid resistance. Hardness is valuable in monitoring compound consistency.
On the environmental resistance side, hot air ageing, swelling in fluids, ozone cracking and low temperature behaviour are examined. FLUID RESISTANCE is particularly critical: the same elastomer behaves differently in fuel, oil, coolant and brake fluid — swelling in one, shrinking in another, hardening in a third. The material is therefore tested with the actual fluid it will contact and at the actual temperature.
Ozone cracking is a silent cause of failure in parts used outdoors. Low concentrations of ozone in the atmosphere create surface cracks in unsaturated elastomers under strain; the part cracks while appearing to carry no load at all. An ozone chamber accelerates and reveals this behaviour.
Low temperature behaviour is the second silent risk. As an elastomer approaches its glass transition temperature it loses elasticity and behaves like a rigid plastic; a gasket starts to leak in the cold. Low temperature recovery and brittleness tests establish this limit.
A change of compound is not a silent change in this family. When filler content, plasticiser or the vulcanisation system changes, mechanical properties and fluid resistance shift together; verification is repeated.
Method groups in this field
Mechanical
Tensile stress-strain properties, tear strength, abrasion (rotating drum and Pico), fatigue and tear propagation.
Hardness
Shore A and IRHD indentation hardness; a rapid indicator of compound consistency.
Permanent deformation
Compression set and stress relaxation; decisive for sealing components.
Fluid resistance
Swelling in fuel, oil, coolant and chemicals, change in mass and volume, loss of hardness and strength.
Ageing
Hot air ageing, ozone cracking, the effects of UV and humidity.
Low temperature
Low temperature recovery, brittleness temperature and flexibility measurements.
Commonly confused in this field
- Hardness does not define the material; two compounds of the same hardness can show different ageing and fluid resistance.
- Fluid resistance must be tested with the actual fluid and the actual temperature; a general claim of oil resistance is insufficient.
- Without measuring compression set, no decision can be made about sealing life.
- Ozone cracking occurs under strain; a test with an unstrained specimen does not show the real risk.
- A change of compound requires verification to be repeated; a supplier may change its compound silently.
- A gasket whose low temperature behaviour is not stated produces unexpected leaks in cold climates.
Which decisions these results support
- Material selection for gaskets and sealing components
- Automotive and industrial component approval
- Verification of a compound change
- Root cause analysis of field leaks and cracking
- Declaration of the operating temperature range and fluid compatibility
Related Tests
Frequently Asked Questions About Elongation
According to which standard is Elongation made?
Elongation is executed in scope ISO 37, ASTM D412 and ISO 23529. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.
Which products does Elongation apply to?
Mainly applied to Gaskets and sealing elements, Elastomer profiller, Hoses and bellows and rubber coatings. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Elongation done?
The determining parameters are: Measurement — Measurement length with extensometer; gauge length is used instead of jaw separation, Tensile speed — Defined in standard and Conditioning — according to ISO 23529. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.
What kind of sample is needed for Elongation?
Sample edges must be flawless, Size markings must be clear and The sliding jaw must hold the sample without nicking it. The number of samples is determined according to the product standard and the scope to be reported.
How long does Elongation take?
Typically 2–4 days including conditioning. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.
What is the Elongation result called "appropriate"?
The acceptance criterion is the minimum breaking elongation value given in the specification.