Discussion on Common Problems in Artificial Weathering Accelerated Aging Tests
Polymer materials such as plastics, rubber, and coatings often face aging issues during their service life. To evaluate the resistance of these materials to aging, two primary testing methods have been developed: natural aging tests and artificial accelerated aging tests. Natural aging involves exposing materials directly to real-world environmental conditions, while artificial accelerated aging simulates key aging factors—such as sunlight, temperature, humidity, and rainfall—in a controlled laboratory environment.
Natural aging is considered the most reliable method due to its direct correlation with real-world conditions. However, it can be time-consuming, and variations in climate across different regions and seasons make results difficult to compare. In contrast, artificial accelerated aging allows for faster and more reproducible testing by controlling variables like UV exposure, heat, and moisture. This makes it an essential tool in material development and quality assurance.
During artificial accelerated aging tests, several critical questions arise: What test conditions should be used? How long should the test last? Which performance indicators should be measured? This article explores these challenges and provides insights into best practices for conducting effective accelerated aging tests.
1. Selection of Artificial Accelerated Aging Test Conditions
Choosing the right test conditions depends on the material’s intended use and the main aging factors it will encounter. For example, PVC profiles used outdoors are exposed to UV light, heat, oxygen, and moisture. The national standard GB/T 8814-2004 specifies both photo-oxidation and thermal oxygen aging tests to simulate these conditions. Similarly, for shoes exported internationally, UV aging tests are conducted to assess color stability, while heat and humidity tests simulate shipping environments.
2. Light Source Selection for Artificial Aging
The choice of light source significantly affects test outcomes. Xenon arc lamps are widely used because their spectral distribution closely resembles natural sunlight. Fluorescent UV lamps, while more cost-effective, may not accurately replicate all aspects of natural UV exposure. Sunlight-type carbon arc lamps, though less common in China, are still used in Japan for certain standards. Each light source has its advantages and limitations, and the selection should depend on the specific material and application.
3. Determining Test Duration
Test duration can be based on product standards, known correlations between artificial and natural aging, or by matching total radiation levels. For instance, if a plastic product is expected to withstand one year of outdoor exposure, the artificial test duration can be calculated using irradiance data and acceleration factors. This approach ensures that the test reflects real-world conditions accurately.
4. Selecting Performance Evaluation Indicators
Evaluation criteria vary depending on the material's use and properties. For decorative coatings, appearance changes like gloss and color shift are important. For functional coatings, crack resistance and chalking might be more relevant. For engineering plastics, impact strength is a key indicator, while for polyethylene, elongation at break is crucial. Standards often define specific thresholds for acceptable performance after aging.
5. Conclusion
Artificial accelerated aging tests provide a fast and reliable way to evaluate material durability. They complement natural aging tests and are essential in polymer research and quality control. Understanding how to select test conditions, light sources, durations, and evaluation metrics is vital for accurate and meaningful results. This article offers guidance to help researchers and engineers optimize their testing strategies.