How to evaluate the weather resistance of silicone pigments?
It can be done from two aspects: simulating natural environment and actual outdoor testing.
Simulating natural environment test
Ultraviolet aging test: Use a UV aging test chamber, set the appropriate UV intensity (such as about 50W/m²) and wavelength (usually between 315-400nm), and put the silicone sample containing silicone color paste into the test chamber. Set the aging time, such as 1000 hours, take out the sample at a certain interval (such as 100 hours), use a colorimeter to measure the color change, record the L* (brightness), a* (red-green), b* (yellow-blue) values of the color, and observe whether cracks, powdering, etc. appear on the surface of the sample. Evaluate weather resistance based on color change and surface condition. Color pastes with small color changes and no obvious surface defects have better weather resistance.
Wet and hot aging test: Place the sample in a wet and hot test chamber, set the temperature to 40℃-60℃ (such as 50℃), and the relative humidity to 80%-95% (such as 90%). After a certain period of time (such as 500 hours), take it out and check the appearance of the sample to see if there is any discoloration, mold, blistering, etc. At the same time, measure the changes in its mechanical properties (such as tensile strength, elongation, etc.). If the performance decreases slightly, it means that the color paste has good weather resistance in a hot and humid environment.
Salt spray corrosion test: Put the sample into the salt spray test chamber and use 5% sodium chloride solution to spray at a certain spray volume (such as 1-2mL/80cm²・h) and test temperature (such as 35℃). After a specified time (such as 240 hours), take it out and observe the corrosion and color changes on the surface of the sample. Color pastes with strong salt spray corrosion resistance have better weather resistance in this regard.
Outdoor natural exposure test
Sample preparation: Make multiple silicone samples containing silicone color pastes and mark the relevant information of the samples, such as color paste type, number, etc.
Selection of exposure site: Select a representative outdoor environment, such as the seaside (simulating high humidity and salt spray environment), industrial area (simulating environment with polluted gas), plateau area (simulating strong ultraviolet environment), etc. Fix the sample on a suitable bracket so that it can be fully exposed to the natural environment.
Regular inspection: Check the sample every once in a while (such as one month, three months, half a year, etc.). Observe the color change of the sample, and use a colorimeter for precise measurement; check whether there are cracks, peeling, powdering, etc. on the surface; test whether its physical properties (such as hardness, elasticity, etc.) have changed. Based on these inspection results, comprehensively evaluate the weather resistance of silicone color paste in natural environment.