Introduction
In the field of materials science, evaluating the long-term durability of polymer materials is a critical task. Ozone, as a strong oxidizing gas, is widely present in the atmosphere and is one of the main environmental factors that cause aging cracking in many polymers, especially elastomers containing unsaturated bonds. By simulating and accelerating this process, ozone aging testers provide a scientific and reproducible testing method for evaluating the crack resistance of rubber products. The purpose of this paper is to explore the working principle, test method and application of the testing machine in the evaluation of rubber crack resistance.
Principle of equipment
Ozone aging testers work primarily by creating a closed environment with controllable concentration, temperature, and humidity. At its core, rubber specimens are exposed to air streams containing a certain concentration of ozone, and the specimens are usually subjected to a certain static or dynamic tensile strain to simulate stress states in actual use. Ozone molecules attack the unsaturated bonds in the rubber molecular chain, causing chain breaks and crosslinking changes, eventually forming visible cracks on the surface of the specimen. By controlling ozone concentration, exposure time, ambient temperature, and specimen strain, this aging process can be accelerated, allowing for the long-term weathering resistance of the material to be evaluated in a shorter period of time.
Test Standards
In order to ensure the reliability and comparability of test results, a number of relevant standards have been established at home and abroad. These standards specify in detail key parameters such as test conditions, sample preparation, and evaluation methods. Adhering to uniform standards is crucial for material development, quality control, and product certification.
| Standard system | Standard numbering and naming points |
| International standards | ISO 1431-1: Determination of ozone cracking resistance of rubber (static strain test) |
| Chinese standard | GB/T 7762: Ozone aging test for vulcanized rubber (static tensile test) |
| American standard | ASTM D1149: Test Method for Ozone Cracking of Rubber in Confined Environments |
| European standard | DIN 53509-1: Rubber test - Determination of resistance to ozone cracking |
Evaluation methodology
The evaluation of ozone crack resistance of rubber is mainly based on the time of crack appearance, the density, length and depth of the crack. Common evaluation methods include:
Visual observation method:At specified intervals, the surface of the specimen is observed through a magnifying glass or microscope, and the time of the first crack is recorded, or the degree of cracking is evaluated according to a standard grade map. Crack grades are usually divided from grade 0 (no cracking) to grade 4 (severe cracking).
Performance rate change method:The physical and mechanical properties of the specimen before and after aging, such as changes in tensile strength and elongation at break, are tested. Performance retention can be calculated using the following formula:
Performance Retention = (Performance Value after Aging / Performance Value Before Aging) × 100%
Among them, the decrease of elongation at break is usually more sensitive to ozone aging, which is an important index for evaluating cracking resistance.
Key influencing factors
Test results are influenced by a variety of factors, and understanding and controlling them is crucial for accurate data.
| Influencing factors | Brief description |
| ozone concentration | The higher the concentration, the faster the aging rate. Commonly tested concentrations are 25pphm to 200pphm. |
| Ambient temperature | Rising temperature accelerates the reaction rate of ozone with rubber. The standard test temperature is usually 40°C. |
| Specimen strain | The magnitude of the applied tensile strain directly affects the initiation and growth rate of cracking. |
| Rubber formulation | The type and amount of anti-ozone agents, as well as the resistance of highly saturated rubber (such as EPDM), are better. |
Application and Significance
Ozone aging test is widely used in the research and development and quality control of various rubber products such as automotive seals, cable jackets, conveyor belts, and waterproof membranes. Through this test, material formulations with better weather resistance can be screened, predicting the service life of products in ozone-containing environments, and providing key data support for product design, material improvement, and quality assurance. It helps engineers identify potential failure risks before products are put into actual use.
Conclusion
Ozone aging tester is an effective tool for evaluating the environmental cracking resistance of rubber materials. By simulating ozone erosion conditions and combining standardized testing and evaluation methods, quantitative data on the aging resistance of materials can be obtained relatively quickly. In practical applications, it is necessary to comprehensively consider test standards, environmental parameters and material characteristics to make more scientific and reliable judgments on the long-term durability of rubber products.
References
1. In the introduction and equipment principle section, the relevant review literature on the aging mechanism of polymer materials is referenced.
2. The test standard part is organized from the current standard texts of ISO, GB, ASTM and DIN.
3. The evaluation method and key influencing factors section synthesizes the views from the rubber testing technical manual and a number of material durability research papers.