You may have noticed in life that some TPU products are affected by ultraviolet rays. After a period of use, some yellowing occurs more or less. What is the cause of the yellowing?
There is a section called hard segment in the high molecular weight of TPU. The double benzene ring structure of the MDI material in it is unsaturated and easily oxidized under ultraviolet rays. This oxidation causes quinone change in color, which is what we call yellowing. So how can we improve it?
Usually we add two things: one is ultraviolet absorber, and the other is antioxidant. Mixing these two substances and adding them can reduce the intensity of ultraviolet rays, improve the ultraviolet resistance of TPU, and make the hard segment less likely to be oxidized, thereby greatly delaying the yellowing of TPU that may occur after long-term use.