Ultraviolet absorber is a kind of light-stabilizing plastic additive stabilizer, which produces a stabilizing effect by absorbing and transforming the destructive ultraviolet light part of sunlight. Ultraviolet absorbers are sometimes added to the film of packaged food in order to inhibit the effect of ultraviolet light on the packaged item.

Under normal circumstances, if the film does not add ultraviolet absorbers, when used outdoors, it begins to become brittle in two months, when adding ultraviolet absorbers, it can be extended to 13 months after the film elongation began to decline sharply, and the film service life can reach more than one year.

It is necessary to add ultraviolet absorbent to agricultural film. The test proves that when the amount of ultraviolet absorber is 0.2 parts. The exposure time of the film can be extended from three months to about one year (depending on the specific formulation design). Commonly used UV absorbers are benzophenone, benzotriazole, triazine, salicylate.

Only a narrow range of light waves in daylight have a degradation effect on PVC, the most harmful is the wavelength of 3 soil 0 nm of light waves, which is the central band of ultraviolet light.

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

Now the performance of several commonly used plastic additives UV absorbers is listed in Table 1-7.

Among the several commonly used plastic additives ultraviolet absorbers introduced in the above table, UV— 531, UV-9, UV-P, TBS, RMB, etc., the light stabilization effect is more significant, generally can make the film withstand about 15 months of outdoor exposure. The light stabilization effect of triazine is more prominent. Triazine, UV— 531, UV— 9, UV-P, UV— 0 Strong absorption of light waves with a wavelength of 290 ~ 340 nm, and the transmittance is below 15%. BAD has excellent weather resistance, 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, ultraviolet absorbers have the best effect, including substances that can be transformed into ultraviolet absorbers under the action of light. H.P.T. and phenyl salicylate have a very weak ability to absorb ultraviolet light, poor light stability, but still have a certain light resistance effect, exposure to a year to produce spots. TBS and RMB also have a weak ability to absorb ultraviolet rays, but have good weather resistance, and spots only appear after 15 months of exposure, which is due to the rearrangement of 2, 4-dihydroxybenzophenone, which absorbs ultraviolet rays strongly under the action of light.

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