What Is Ozone Resistance?
Ozone resistance test is the test where the sample stretched at a defined rate is kept at a certain ozone concentration, temperature and humidity; It is an experiment in which crack formation on the surface is monitored.
Purpose of Ozone Resistance
The aim is to verify that elastomers to be used outdoors are protected against ozone cracking.
Which Products Is Ozone Resistance Applied To?
- Outdoor gaskets and profiles
- Hose and belts
- Automotive rubber parts
- Cable sheaths
In Which Sectors Is Ozone Resistance Used?
Standards Related to Ozone Resistance
- ISO 1431-1
- ISO 1431-3
- ASTM D1149
- ISO 23529
Ozone Resistance Conditions
- Ozone concentration
- Defined in the standard; It is given as partial pressure in ppm or mPa and is constantly monitored
- Strain
- Static elongation (typically 20%) or dynamic strain
- Temperature and humidity
- Defined in the standard; typically 40 °C
- Time
- Defined in the specification; typically 72 or 96 hours
Equipment for Ozone Resistance
- Ozone test cabinet and ozone generator
- Ozone concentration measurement system
- tensioning frames
- Stereo microscope (crack inspection)
Sample Requirements for Ozone Resistance
- The sample stretching ratio must be set correctly
- The sample surface must be clean and flawless.
- Ozone concentration should be recorded throughout the experiment
- Samples must be rested for a period defined in the standard before the experiment.
Duration of Ozone Resistance
4–10 days depending on duration.
Ozone Resistance Procedure
- 1The samples are stretched to the defined ratio.
- 2Cabin ozone concentration, temperature and humidity are adjusted.
- 3Samples are exposed for a defined period of time.
- 4The surface is examined at regular intervals with magnification.
- 5The presence and severity of cracks are graded.
- 6The result is reported.
Ozone Resistance Acceptance Criteria
Acceptance criteria are given in the specification; Typically, it is desired that there are no cracks under magnification after a defined period of time.
Evaluation of Results
Failure to monitor the ozone concentration throughout the experiment invalidates the result; Ozone is depleted in the cabin. The stretching ratio is also decisive: ozone cracking is usually not visible in the unstressed sample.
Ozone Resistance Report
- Standard applied
- Ozone concentration records
- Stretch ratio
- Temperature, humidity and duration
- Crack rating and images
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
- Automotive and outdoor product specifications
Rubber Testing — What Does This Testing Field Cover?
The section below describes the field that the Ozone Resistance 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 Ozone Resistance
According to which standard is Ozone Resistance made?
Ozone Resistance is executed in scope ISO 1431-1, ISO 1431-3, ASTM D1149 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 Ozone Resistance apply to?
Mainly applied to Outdoor gaskets and profiles, Hose and belts, Automotive rubber parts and Cable sheaths. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Ozone Resistance done?
The determining parameters are: Ozone concentration — Defined in the standard; It is given as partial pressure in ppm or mPa and is constantly monitored, Strain — Static elongation (typically 20%) or dynamic strain and Temperature and humidity — Defined in the standard; typically 40 °C. 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 Ozone Resistance?
The sample stretching ratio must be set correctly, The sample surface must be clean and flawless. and Ozone concentration should be recorded throughout the experiment. The number of samples is determined according to the product standard and the scope to be reported.
How long does Ozone Resistance take?
4–10 days depending on duration. 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 Ozone Resistance result called "appropriate"?
Acceptance criteria are given in the specification; Typically, it is desired that there are no cracks under magnification after a defined period of time.