Hindered amine light stabilizers selection

The stabilizers chosen for evaluation include different types of heat and light stabilizers selected to represent different mechanisms of action as well as chemical compositions (ArJi). Types of stabilizers evaluated include benzotriazole and benzophenone light stabilizers [ultraviolet (UV) light absorbers], hindered amine light stabilizers (HALS, catalytic radical scavengers), hindered phenol heat stabilizers (antioxidant radical scavengers), and thioester heat stabilizers (antioxidant hydroperoxide decomposers). 

The most common UV absorbers used commercially are hindered amine light stabilizers, which can also function as heat stabilizers in some plastics. Other UV absorbers include benzotriazoles and benzophenones, salicylate esters, cyanoacrylates, malonates and benzilidenes. Factors such as the nature of the resin, type and level of pigments being used, and the presence of crosslinkers and catalysts govern the selection of UV absorber to be used. 

The most important classes of UV stabilizers are UV absorbers (U VAs), quenchers and hindered amine light stabilizers. In this chapter an overview is given about the types of UV stabilizers in use, their mechanisms of action as well as possible synergistic and antagonistic effects. In the last part for a selected number of polymers the effectiveness of different stabilizers is shown. The chemicals structures of all stabilizers mentioned in this chapter are shown in Appendix 17.9. 

Selected suppliers are promoting hindered amine light stabilizers for the combined use as antioxidants. 

A polyolefin fiber may comprise a mixture of a phosphite, to provide thermal and ultraviolet light stabilization, and an additive selected from a hindered phenolic antioxidant or hindered amine light stabilizer [32]. ... 

Hindered amines are generally classified as light stabilizers. The three selected products are derivatives of 1,6-hexanediamine and are effective antioxidants for polyolefins. 

The selection of sterically hindered amines for light protection is also often determined by side-effects. In some cases, the side-effects are so significant that light protection almost becomes a secondary effect. For instance, Nylostab S-EED developed specifically for PA, is mainly used for its process stabilizing and color improving effects. Fig. 3.9 [510]. 

Blends of long chain A,A -diallylhydroxylamines, selected phosphites, and selected hindered amines are effective in providing processing, long term heat and light stability performance, and especially gas fade... 

---