When performing light fastness testing of plastic materials, there are often special requirements that need to be considered because plastic materials are different from other materials such as textiles or dyes. The following are some common special requirements for light fastness testing of plastic materials:

1. Selection of light source: Choose a suitable light source to simulate the light conditions in the actual use environment. Light sources commonly used in lightfastness testing of plastic materials include ultraviolet (UV) lamps, xenon lamps, and fluorescent lamps. These light sources are capable of producing light close to the actual solar spectrum.

1. Testing temperature: Plastic materials may be more susceptible to color change or fading in hot environments. Therefore, the test temperature needs to be taken into account when conducting light fastness color fastness tests. The appropriate test temperature is usually set according to the actual conditions of use. 1.

1. Exposure time: Plastic materials usually have better light fastness than other materials such as textiles, so the test time may need to be longer. Depending on the characteristics of the plastic material and the test requirements, an appropriate exposure time can be selected, which may take several hundred hours or more.

1. Observation methods: For plastic materials, it is often necessary to use appropriate observation methods to assess color changes. Methods such as colorimetry, spectroscopy, or visual inspection can be used to measure color differences before and after exposure to light.

1. Assessment criteria: The criteria for assessing color fastness to light for plastic materials may differ from those for materials such as textiles or dyes. Relevant international standards (e.g. ISO, ASTM) or industry standards need to be referred to in order to determine the assessment metrics and scoring system applicable to plastic materials.

These specific requirements can help ensure accurate and reliable light fastness testing of plastic materials and assess their performance under actual conditions of use. Please note that specific test requirements and methods may vary depending on the application and industry, and it is recommended to refer to the relevant standards and guidelines for more detailed and specific information.