Overview
The UV Aging Tester accelerates the aging process of materials by simulating the UV bands in the solar spectrum, combined with temperature and humidity control. Its core light source usually uses fluorescent ultraviolet lamps, which can stably output radiation in the UVA or UVB bands. The device can precisely control parameters such as irradiance, blackboard temperature, and condensation cycle, providing a repeatable testing environment for evaluating the weathering resistance of inks and other materials.
Influencing factors
The UV resistance of inks depends on their chemical composition and film-forming properties. The lightfastness of the pigment or dye, the stability of the resin system, and the type of light stabilizer added can all affect the final performance. Under UV radiation, ink coatings can undergo photooxidation reactions, leading to color fading, surface chalking, or reduced adhesion. By quantifying these changes, the durability rating of the ink can be systematically evaluated.
Test conditions
The test needs to be set according to relevant standards (e.g., ASTM G154, ISO 4892-3). A typical cycle can include a UV illumination phase and a condensation phase, with the blackboard temperature usually set at 50°C to 70°C and irradiance controlled at 0.5 W/m² to 1.5 W/m² (at 340nm). The total test duration can range from hundreds to thousands of hours, depending on the application requirements. The following are examples of common test parameters:
| Light phase temperature | 60°C ±3°C |
| Condensation stage temperature | 50°C ±3°C |
| UV irradiance (340nm) | 0.89 W/m² |
| Single cycle duration | 8 hours of light + 4 hours of condensation |
| Total test duration | 300 hours to 1500 hours |
Evaluation methodology
The evaluation mainly revolves around color stability, physical properties and chemical structure changes. Chromatic aberration (ΔE) can be measured by a spectrophotometer and calculated with reference to the CIELAB color space. The change in gloss was measured at an angle of 60° using a gloss meter. Adhesion can be tested by the grid method. Chemical structure analysis can be performed by Fourier transform infrared spectroscopy (FTIR) to detect functional group changes. The color change rate can be approximated by the following formula:
ΔE = √(L₂ - L₁)² + (a₂ - a₁)² + (b₂ - b₁)²
L, a, and b are the chromaticity values of the samples before and after aging. The higher the ΔE value, the more pronounced the color change.
Application Recommendations
The test results should be interpreted in conjunction with the actual use environment of the ink. For example, inks for outdoor signage need to focus on color aberration and chalking, while packaging printing inks may focus more on gloss retention. It is recommended to use UV aging testing as a routine validation item during the development stage, and adjust the ratio of pigments to resins in the formulation based on the results, or add an appropriate amount of UV absorbers to improve weather resistance. Regularly compare test data to establish a material property database and provide a basis for product improvement.
References
ASTM G154-16, Standard Practice for Operating Fluorescent Ultraviolet Lamp Apparatus for Exposure of Nonmetallic Materials.
ISO 4892-3:2016, Plastics — Methods of exposure to laboratory light sources — Part 3: Fluorescent UV lamps.
CIELAB color space specification, CIE Publication No. 15.