Ultraviolet absorber is a kind of plastic auxiliary stabilizer that plays a role in light stabilization. It produces a stabilizing effect by absorbing and transforming the destructive part of ultraviolet light in sunlight. Ultraviolet absorbers are sometimes added to the film for packaging food in order to suppress the effect of ultraviolet light on the packaged items.

In general, if no ultraviolet absorber is added to the film, it will become brittle when used outdoors in two months. When the ultraviolet absorber is added, it can be extended to 13 months before the film elongation rate begins to decline sharply. The service life of the film can also reach more than one year.

　　It is necessary to add ultraviolet absorbers to agricultural films. The test proves that when the ultraviolet absorber is added in an amount of 0.2 parts. The film exposure time can be extended from three months to about one year (depending on the specific formulation design). Commonly used ultraviolet absorbers are benzophenones, benzotriazoles, triazines, and salicylates. .

　　There is only a narrow range of light waves in sunlight that has a degrading effect on polyvinyl chloride. The most harmful is the light wave with a wavelength of 3 ± 0 nm, which is the central band of ultraviolet light

　　In practice, it has been proved by application that under the condition of 0.3 parts, the absorption effect of the triazine ultraviolet absorber is much better than that of UV-9, which can be clearly seen from the spectral curve of the film in the ultraviolet region.

The properties of several commonly used plastic additives UV absorbers are listed in Table 1-7.

Among the several commonly used plastic additives ultraviolet absorbers introduced in the table above, UV-531, UV-9, UV-P, TBS, RMB, etc. have a more significant light stabilizing effect, and generally can make the film withstand outdoor for about 15 months Exposure. The light stabilizing effect of triazine is more prominent. Triazine, UV-531, UV-9, UV-P, and UV-0 have strong absorption of light waves with a wavelength of 290 to 340 nanometers, and their transmittances are all below 15%. The weather resistance of BAD is excellent, the elongation of the film is still 80% after 19 months of exposure, and no spots have been produced after 20 months of exposure. In summary, UV absorbers are the most effective, including substances that can be converted into UV-absorbing substances under the action of light. The ability of HPT and phenyl salicylate to absorb ultraviolet rays is very weak, and the light resistance and stabilization are poor, but it still has a certain light resistance effect, and spots will be produced after one year of exposure. TBS and RMB are also weak in absorbing ultraviolet rays, but the weather resistance is very good. Spots appear only after 15 months of exposure. This is due to the rearrangement of 2,4-dihydroxybenzophenone, which absorbs ultraviolet rays very strongly under the influence of light. To.