What Is Ozone?
The ozone resistance test evaluates the cracking behaviour of strained rubber specimens in an ozone-containing environment. Ozone causes surface cracks in rubbers containing unsaturated bonds; these cracks cause rapid degradation, especially in strained gaskets and hoses.
Purpose of Ozone
The purpose is to determine whether the rubber component resists cracking under atmospheric ozone, and to verify the adequacy of the antiozonant additive system.
Which Products Is Ozone Applied To?
- Door and window seals
- Engine-bay hoses
- Rubber bellows and boots
- Vibration mounts
- Belts
In Which Sectors Is Ozone Used?
Standards Related to Ozone
- ISO 1431-1
- ISO 1431-3
- ASTM D1149
- ASTM D518
Ozone Conditions
- Ozone concentration
- At the concentration prescribed by the standard (commonly 25, 50 or 200 pphm)
- Temperature
- Commonly 40 °C ± 2 °C
- Strain
- Static strain percentage per the specification (commonly 20%)
- Pre-conditioning
- Specimens are held under strain in an ozone-free environment
Equipment for Ozone
- Ozone test chamber and ozone generator
- Ozone-concentration analyser
- Specimen-straining frames
- Magnifier or stereo microscope (for crack assessment)
Sample Requirements for Ozone
- Strip specimens prescribed by the standard
- Generally at least three specimens
- The specimen surface must be free of cutting marks
- The compound code and curing conditions must be stated
Duration of Ozone
Exposure duration varies by specification; common stages are 24, 48, 72 and 96 hours. Together with pre-conditioning, the total duration is a few days.
Ozone Procedure
- 1Specimens are cut and verified to be flawless.
- 2They are strained in the frame at the specified strain percentage.
- 3Pre-conditioning is performed in an ozone-free environment.
- 4The chamber's ozone concentration and temperature are set and verified.
- 5Specimens are placed in the chamber.
- 6Specimens are examined for cracks under a magnifier at specified intervals.
- 7Crack-initiation time and crack severity are recorded.
Ozone Acceptance Criteria
The acceptance criterion is determined per the specification; common practice is the absence of cracks visible by eye, or at a specified magnification, at the end of the specified duration. If a crack-grading scale is used, the maximum permitted grade is defined in the specification.
Evaluation of Results
Crack initiation time, number and depth are evaluated. Strain percentage directly affects the result; the same strain condition must therefore be used in comparisons.
Ozone Report
- Standard applied
- Specimen description and compound information
- Ozone concentration, temperature and strain percentage
- Exposure duration and interim observations
- Crack status and grading
- Photographs
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
- OEM rubber-material specifications
Otomotiv Testleri — What Does This Testing Field Cover?
The section below describes the field that the Ozone 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.
Automotive testing shows that a component keeps working under conditions representing the loads it will meet over the life of the vehicle. A vehicle is not a single product but an ENVIRONMENT: vibration, temperature cycling, salt water, stone impact, electrical transients and electromagnetic noise are all present at the same time and for years.
What distinguishes this family is that VEHICLE MANUFACTURER SPECIFICATIONS sit on top of the standards. ISO and SAE publications establish the common ground; but Volkswagen, BMW, Ford, Stellantis, Toyota and Renault define different severity levels, additional tests and different acceptance criteria in their own specifications. For a component, the phrase "complies with automotive standards" is not sufficient on its own; which manufacturer's specification, and which revision of it, must be answered.
The family carries three separate processes together and they are often confused. Homologation covers the type approvals a vehicle needs to enter traffic and runs under state authority. Supplier approval means passing the vehicle manufacturer's own quality and testing requirements and is a commercial relationship. The third is design verification: the engineering team demonstrating that its own design meets its targets.
At component level the test plan is built around the LOCATION OF USE. A module in the engine bay and a module in the boot do not go through the same temperature and vibration profile; a component inside a door and one in the roof console do not see the same water and dust exposure. The ISO 16750 series is the common framework for this location-based approach.
The shift to electric vehicles has reshaped the field. High-voltage safety, insulation coordination, battery safety, charging interface conformity and the electromagnetic behaviour of high-voltage components have been added to the classical automotive test set. In a quiet vehicle, acoustic and vibration expectations have changed too; sounds once masked by the combustion engine are now audible.
The quality system side cannot be separated from testing in this field. A manufacturer under IATF 16949 presents test results in the PPAP file; measurement system analysis, process capability study and the control plan stand around the test report. A single good result is not enough — the process must be shown to be able to repeat it.
Method groups in this field
Environmental and climatic
Temperature cycling, thermal shock, damp heat, salt spray, dust and water ingress (IP), solar radiation. Severity levels vary with the mounting location.
Mechanical
Sine and random vibration, shock, mechanical loads, fastener torque and durability cycles.
Electrical
Supply voltage variations, transients (ISO 7637), reverse polarity, overvoltage, short circuit and sleep current measurements.
EMC
Component emissions (CISPR 25), radiated and conducted immunity (ISO 11452 series), electrostatic discharge (ISO 10605).
Materials and emissions
Odour, fogging and VOC emissions from interior materials; flammability; UV ageing; coating durability and stone impact.
Functional safety and cyber security
Functional safety evidence under ISO 26262 and cyber security engineering under ISO/SAE 21434; these are tied to regulation through UNECE R155 and R156.
Commonly confused in this field
- An automotive report without a specification reference is not accepted in the supply chain; which OEM specification and revision was applied must be stated.
- Type approval and supplier approval are different processes. A component with E-Mark approval is not thereby considered to have passed the OEM's own acceptance tests.
- A result obtained on a prototype does not carry over to series production; PPAP is done with series production parts.
- On the EMC side, measuring emissions alone is incomplete; immunity is a separate body of work and is more critical in a vehicle.
- On electric vehicle components, high-voltage safety is a distinct competence; classical 12 V test infrastructure is not sufficient.
Which decisions these results support
- Supplier component approval and the PPAP file
- UNECE type approval and E-Mark marking
- Design verification and durability evidence
- Root cause analysis of field complaints and warranty returns
- Assessing the impact of a design or supplier change
Related Tests
Frequently Asked Questions About Ozone
How is ozone cracking recognised?
Ozone cracks begin on the surface as fine, parallel lines perpendicular to the strain direction. This characteristic appearance distinguishes ozone degradation from other types of ageing.
Which rubbers are sensitive to ozone?
Rubbers with unsaturated bonds in the main chain (NR, SBR, NBR, BR) are sensitive. EPDM, silicone and fluorocarbon rubbers are far more resistant owing to their structure. An antiozonant additive must be used in sensitive rubbers.