What Is Tensile Strength?
Rubber tensile strength test is the test in which the breaking strength, stress (module) at defined elongations and elongation at break are determined by pulling a standard shovel or ring sample at a constant speed.
Purpose of Tensile Strength
The aim is to verify the consistency of mixing and vulcanization by checking the strength properties of vulcanized rubber.
Which Products Is Tensile Strength Applied To?
- Gasket and O-ring materials
- Hose and belts
- Vibration mounts
- rubber coatings
In Which Sectors Is Tensile Strength Used?
Standards Related to Tensile Strength
- ISO 37
- ASTM D412
- ISO 23529 (sample preparation and conditioning)
Tensile Strength Conditions
- Specimen
- Type 1–4 spade or ring specimen as defined in ISO 37
- Tensile speed
- Defined in the standard; typically 500 mm/min
- Conditioning
- Defined period at 23 °C ± 2 °C according to ISO 23529
- Quantities measured
- Breaking strength, breaking elongation, tensile at 100%/200%/300% elongation
Equipment for Tensile Strength
- Calibrated tensile tester and low force cell
- Optical or contact extensometer
- sample cutting die
- Thickness measuring device (contact pressure controlled)
Sample Requirements for Tensile Strength
- There should be no notches or edge defects in the sample cutting.
- Thickness must be measured with the contact pressure defined in the standard
- The sample must wait for a period defined in the standard after vulcanization.
- The number of samples is usually at least three, preferably five.
Duration of Tensile Strength
Typically 2–4 days including conditioning.
Tensile Strength Procedure
- 1Samples are die cut and conditioned.
- 2Thickness is measured.
- 3The sample is placed in the grips and the extensometer is attached.
- 4Pulling is applied at a defined speed.
- 5Breaking strength and elongation are recorded.
- 6The median or mean value is reported.
Tensile Strength Acceptance Criteria
The acceptance criteria are the minimum breaking strength and elongation values given in the material specification.
Evaluation of Results
Edge defects initiate premature rupture in the rubber and indicate low strength; sample cutting is effective enough to determine the result. Excessive contact pressure in thickness measurement crushes the soft sample and gives an incorrect high strength calculation.
Tensile Strength Report
- Applied standard and sample type
- Conditioning conditions
- Tensile speed
- Breaking strength, elongation and modulus 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 Tensile Strength 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 Tensile Strength
According to which standard is Tensile Strength made?
Tensile Strength is executed in scope ISO 37, ASTM D412 and ISO 23529 (sample preparation and conditioning). 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 Tensile Strength apply to?
Mainly applied to Gasket and O-ring materials, Hose and belts, Vibration mounts 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 Tensile Strength done?
The determining parameters are: Specimen — Type 1–4 spade or ring specimen as defined in ISO 37, Tensile speed — Defined in the standard; typically 500 mm/min and Conditioning — Defined period at 23 °C ± 2 °C 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 Tensile Strength?
There should be no notches or edge defects in the sample cutting., Thickness must be measured with the contact pressure defined in the standard and The sample must wait for a period defined in the standard after vulcanization.. The number of samples is determined according to the product standard and the scope to be reported.
How long does Tensile Strength 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 Tensile Strength result called "appropriate"?
The acceptance criteria are the minimum breaking strength and elongation values given in the material specification.