Hindered amine light stabilizers polymers

P. Gijsman, J. Hennekens, and D. Tummers, The mechanism of action of hindered amine light stabilizers, Polym. Degrad. Stab. 1993, 39, 225-233. 

R Gijsman, New synergists for hindered amine light stabilizers, Polymer 2002, 43, 1573-1579. 

Gugumus F (1993) Current trends in mode of action of Hindered Amine Light Stabilizers. Polym Degrad Stab 40 167-215... 

Oligomeric hindered amine light stabilizers are effective thermal antioxidants for polypropylene. Thus 0.1% of A[,Af-bis(2,2,6,6-tetramethyl-4-piperadinyl)-l,6-hexanediamine polymer, with 2,4,6-trichloro-l,3,5-triazine and 2,4,4-trimethyl-2-pentaneainine [70624-18-9] (35) (Fig. 5), protects polypropylene multifilaments against oxidation when exposed at 120°C in a forced-air oven (22) for 47 days. 3,5-Di-/ l -butyl-4-hydroxytoluene [128-37-0] (0.1%) affords protection for only 14 days. 

Figure 13.21 shows the resolution of a dozen polymer additives at very high resolution using chloroform as the mobile phase. Tinuvin 622 will elute in pure chloroform whereas Chimassorb 944 and many other hindered amine light stabilizers (HALS) will not. With the addition of 1% triethyl amine to the chloroform, however, virtually all HALS will elute. 

The early recognition of the role of stable nitroxyl free radicals, e.g., 2,2,6,6-tetramethyl-4-oxopiperidine, and their hindered amine precursors, in polymer stabilization soon led to the development of the hindered amine light stabilizer (HALS) class of photoantioxidants. The first HALS, Tinuvin 770, AO-33, (commercialized in 1974) proved to offer much higher UV-stabil-ity to polymers than any conventional UV-stabilizer available at the time such as UV-absorbers, nickel compounds and benzoates. Table 3). 

UV absorbers have been found to be quite effective for stabilization of polymers and are very much in demand. They function by the absorption and harmless dissipation of the sunlight or UV-rich artificial radiation, which would have otherwise initiated degradation of a polymer material. Meyer and Geurhart reported, for the first time in 1945 [10], the use of UV absorber in a polymer. They found that the outdoor life of cellulose acetate film was greatly prolonged by adding phenyl salicylate (salol) [10]. After that, resorcinol monobenzoate, a much more effective absorber, was introduced in 1951 [11] for stabilization of PP, but salol continued to be the only important commercial stabilizer for several years. The 2,4-dihydroxybenzophenone was marketed in 1953, followed shortly by 2-hydroxy-4-methoxybenzophenone and other derivatives. Of the more commonly known UV absorbers, the 2-hydroxybenzophenones, 2-hy-droxy-phenyl-triazines, derivatives of phenol salicylates, its metal chelates, and hindered amine light stabilizers (HALS) are widely used in the polymer industry. 

A polymer-bound hindered amine light stabilizer [P-HALS] has been synthesized by terminating the living anionic polymerization of isoprene with 4(2,3-epoxy pro-poxy)-1,2,2,6,6-pentamethylpiperidine followed by hydrogenation of the resulting polymer to E-P copolymer using Zeigler type catalyst [40] ... 

The hindered-amine light stabilizers for polymers are piperidine derivatives. An example of these products is bis-(2.2,6,6-tetramethyl-4-pipendinyl)sebaeale, tradenained Tinuviii 770, useful as a light stabilizer for polyolefins and styrenics. 

Bauer, L Habicher, W.D. Rauteneberg, C. et al. Antioxidant interaction between organic phosphites and hindered amine light stabilizers during processing and thermoxidation of polypropylene. Polym. Deg. Stab. 1995, 48 (3), 427-440. 

The chemical and physical observations here indicate that biological defacement of polymeric materials is a process precipitated by surface changes. This study suggests that polymers in exterior hostile environments can have significantly delayed surface erosion by the incorporation of light stabilizers. Optimal stabilization of the polymer surface with benzotriazoles and/or hindered amine light stabilizers provides the maintenance of surface integrity and thus increases the material s functional lifetime. 

Since their initial production by our laboratories about ten years ago, hindered amine light stabilizers (HALS) have become established as excellent light stabilizers of polymers. This review deals with their synthesis, evaluation and development. 

Hindered Amine Light Stabilizers (HALS) are a new class of highly efficient stabilizers protecting polyolefins and other polymers against light-induced deterioration. They were initially developed into commercial products in our laboratories. In this review we describe the details of how they were synthesized, evaluated and developed. 

Most hindered amine light stabilizers have evolved from the discovery (4) that compounds containing a 2,2,6,6-tetramethylpiperidine moiety can stabilize polymers against photodegradation and this moiety has been incorporated into HALS of various types (Figure 1). Much has been published on the mechanism of action of HALS and the literature in this area has recently been critically reviewed (5,6). While the complete mechanism of action has not been fully elucidated, the high performance of HALS is generally attributed to the ability of their oxidation products to... 

To make polymers useful for the above-mentioned applications, stabilizers of different types can be added to the polymers. As a result the lifetimes in the outdoor environments becomes long enough to make that polymers can be applied. In fact, without stabilizers the use of polymers in an outdoor environment would be very limited. Especially the discovery of hindered amine light stabilizer (HALS) led to a boost of the applicability of polymers in outdoor environments. 

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. 

D.K. Hodgeman, Formation of polymer-bonded nitroxyl radicals in the UV stabilization of polypropylene by a bifunctional hindered amine light stabilizer, J. Polym. Sci. Polym. Chem. Ed. 1981, 19, 807. 

E.N. Step, J. Turro, M.E. Gande, andP.P. Klemchuck, Mechanism of polymer stabilization by hindered-amine light stabilizers (HALS). Model investigations of the interaction of peroxy radicals with HALS amines and amino ethers, Macromolecules 1994, 27, 2529-2539. 

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