One of the uses of carbon black in the plastics industry is anti-ultraviolet aging. Due to the high absorbance of carbon black, it can effectively prevent photooxidative degradation of plastics caused by sunlight. Carbon black as an ultraviolet light stabilizer plays a role in plastics: converting light energy into heat energy; maintaining plastic appearance to avoid radiation of a certain wavelength; intercepting atomic groups to prevent aging, thereby preventing catalytic degradation. Ultraviolet rays are particularly harmful to polyolefins, and tests have shown that UV shielding can be achieved when the concentration of carbon black of a certain fineness is 2%.
The protective effect of carbon black on the UV aging of plastics depends on the particle size, structure and appearance of the carbon black.
When the particle size of carbon black is small, the absorption of light or shading ability is increased due to the increase in external surface area, so the ultraviolet protection effect is enhanced, but the particle size is less than 20 nm, and the protective effect tends to the same level, because when the particle size is too small, the reverse direction The scattering is reduced, and the light that continues to move forward threatens the stability of the polymer.
The structure is relatively low, that is, when the aggregate size is small, the geometrical volume of the aggregate is small, which enhances the protection of the polymer, which is also the reason why the carbon black of the lower structure is darker.
The carbon black has a large number of oxygen-containing groups, that is, when the volatile matter is high, the gene generated when the polymer is decomposed can be eliminated, and thus the protective effect is also enhanced.
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