selfyellowing

Selfyellowing is a phenomenon observed in certain materials, particularly plastics and polymers, where they undergo a gradual change in color from white or clear to a yellowish hue over time. This process is primarily a result of chemical degradation, often initiated by exposure to ultraviolet (UV) radiation from sunlight, heat, or oxidation. The specific chemical mechanisms involved can vary depending on the material's composition, but typically, the UV light or heat breaks down molecular bonds within the polymer. These broken bonds can lead to the formation of chromophores, which are molecular structures that absorb certain wavelengths of visible light and reflect others, resulting in the perception of color. In the case of selfyellowing, the newly formed chromophores tend to absorb blue and violet light, causing the material to appear yellow. Additives within the plastic, such as antioxidants or UV stabilizers, can slow down or prevent this process, but their effectiveness can diminish over time. Common examples of materials susceptible to selfyellowing include polycarbonate, ABS plastic, and certain types of PVC. The rate and extent of yellowing can be influenced by environmental factors such as the intensity of UV exposure, temperature, and the presence of pollutants.