Light Stabilizer Classes

F. Gugumus, Re-evaluation of the stabilization mechanisms of various light stabilizer classes, Polym. Degrad. Stab. 1993, 39, 117-135. 

T his paper presents a review of the performance and the mechanism of stabilization of a new class of light stabilizers based on substituted piperidine derivatives. These light stabilizers have been found to have outstanding effectiveness in many polymeric substrates. In most instances, the light stability achieved with these compounds was far superior to that attained with conventional light stabilizers. Results of studies illustrating the performance of a representative member of this light stabilizer class, bis(2,2,6,6-tetramethyl-piperidinyl-4) sebacate (LS-1) in polyolefins, styrenics, and polyurethanes are presented in comparison with... 

According to the four possibilities of UV protection mechanism described above, the light stabilizer classes can be designated as (1) UV absorbers, (2) quenchers of excited states, (3) hydroperoxide decomposers, and (4) free radical scavengers. It must be mentioned, however, that this classification is a simplification and that some compounds may be active in more than one way and often do so. 

Among the light stabilizer classes available commercially, only a few may be used in a broad range of plastics. Thus, nickel compounds are used almost exclusively in polyolefins, whereas poly( vinyl chloride) is stabilized with UV absorbers only. 

Light stabilizers are used to protect plastics, particularly polyolefins, from discoloration, embrittlement, and eventual degradation by UV light. The three major classes of light stabilizers are UV absorbers, excited state quenchers, and free-radical terminators. Each class is named for the mechanism by which it prevents degradation. The major types included in each light stabilizer class may be categorized by their chemistries, as shown in Table 4.17. 

For light stabilization of PP representatives of the following light stabilizer classes are mainly used... 

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