Physical properties of commonly used plastic additives UV absorbers
Ultraviolet absorber is a light-stabilizing plastic additive stabilizer that produces a stabilizing effect by absorbing and transforming the destructive ultraviolet light portion of sunlight. Ultraviolet absorbers are sometimes added to the film of the packaged food in order to suppress the effect of ultraviolet light on the packaged article.
Under normal circumstances, if no UV absorber is added to the film, it will become brittle in two months when used outdoors. When the UV absorber is added, the elongation of the film will start to drop sharply after 13 months. The film life can also be more than one year.
It is necessary to add an ultraviolet absorber to the agricultural film. The test proved that the amount of the ultraviolet absorber added was 0.2 parts. The film exposure time can be extended from three months to a year (depending on the specific formulation design). Commonly used ultraviolet absorbers are benzophenones, benzotriazoles, triazines, salicylates. .
There is only a narrow range of light waves in the daylight that degrades polyvinyl chloride. The most harmful is the light wave with a wavelength of 3 earth 0 nm, which is the central band of ultraviolet light.
In practice, it has been proved by application that the absorption effect of the triazine-based ultraviolet absorber is much better than that of UV-9 under the condition of 0.3 parts, which can be clearly seen from the spectroscopic curve of the film in the ultraviolet region.
The performance of several commonly used plastic additives UV absorbers is listed in Table 1-7.
Among the several commonly used plastic additives UV absorbers mentioned above, UV-531, UV-9, UV-P, TBS, RMB, etc. have relatively stable light stability, and generally can make the film withstand for 15 months or so. Exposure. The light stabilizing effect of triazine is more prominent. Triazine, UV-531, UV-9, UV-P, UV-0 have a strong absorption of light waves with a wavelength of 290-340 nm, and the transmittance is below 15%. The weather resistance of BAD is excellent, the elongation of film exposure is still 80% at 19 months, and no spots have been generated after 20 months of exposure. In summary, the ultraviolet absorber has the best effect, and can be converted into a substance that can absorb ultraviolet rays under the action of light. The ability of H.P.T. and phenyl salicylate to absorb ultraviolet light is weak, and the light stability is poor, but there is still a certain light-resistance effect, and spots are generated after exposure for one year. TBS and RMB absorb UV light, 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 is very strong in UV absorption under the action of light. To.