One of the uses of carbon black in the plastic industry is to prevent ultraviolet aging. Because of its high absorbability, the carbon black can effectively prevent the plastic from photooxidative degradation by sunlight. The role of carbon black as an ultraviolet stabilizer in plastics is to convert light energy into heat energy; protect the surface of the plastic to avoid radiation from a certain wavelength; intercept the atomic mass to prevent aging and prevent catalytic degradation. Ultraviolet radiation is particularly harmful to polyolefins. Experiments show that when a certain fineness of carbon black concentration is two percent, it can achieve the perfect UV shielding effect.
The protective effect of carbon black on ultraviolet aging of plastics depends on the size, structure and surface chemistry of carbon black.
When the particle size of carbon black is smaller, the absorption light or shading capacity increases as the surface area increases, so the ultraviolet protection is enhanced, but the particle size is less than 20nm, and its protective effect tends to the same level. The reason is that the reverse scattering decreases when the particle size is too small, and the continued light will threaten the stability of the polymer.
The structure is low, that is, the size of the aggregate is small. Because of the small size of the aggregate, it will enhance the protection of the polymer, which is also the cause of the black carbon black with the lower structure.
There are more oxygen groups on the surface of carbon black, that is, when volatiles are higher, the genes produced by polymer decomposition can be eliminated, so the protection effect is also enhanced.