Light stabilizers examples

Further improvement in light stability may be achieved by addition of small quantities of ultraviolet absorbers. Typical examples include phenyl salicylate, 2,4-dihydroxybenzophenone, resorcinol monobenzoate, methyl salicylate and stilbene. 

Polybutadienes, polycaprolactones, polycarbonates, and amine-terminated polyethers (ATPEs) are shown in Scheme 4.4 as examples of other commercially available polyols. They are all specialty materials, used in situations where specific property profiles are required. For example, ATPEs are utilized in spray-applied elastomers where fast-reacting, high-molecular-weight polyamines give quick gel times and rapid viscosity buildup. Polycarbonates are used for implantation devices because polyuredtanes based on them perform best in this very demanding environment. Polycaprolactones and polybutadienes may be chosen for applications which require exceptional light stability, hydrolysis resistance, and/or low-temperature flexibility. 

Figure 3.22) [22]. Another typical example of a new, evolutionary high-MW hindered amine stabiliser (HMW HAS), with new levels of light stability and reduced interaction with pigments, is Chimassorb 2020 (Fig. 3.25e). 

The molecular encapsulation of flavors with cyclo-dextrins was found to improve the resistence of light sensitive flavor constituents against daylight and ultraviolet irradiation. The photodecomposition of adsorbed and complexed flavors was tested both in the solid state and in aqueous solutions. The results of the light stability tests are demonstrated in the example of complexed and adsorbed citral,beta-ionone and cinnamaldehyde formulations /Table III./. 

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. 

Of the bis(trifluoromethyl)cadmium derivatives obtained to date, the glyme adduct, (CF3)2Cd glyme, is the best compromise between chemical reactivity and thermal stability this compound appears to be almost a classic example of a lightly stabilized species, one which is stabilized enough to be isolatable but which is still quite reactive (107). That this material is a much more effective reagent than, for example, (CF3)2Cd 2 pyridine, can be most easily seen from the results of the reactions of these compounds with a second class of substrates, the halides of germanium and tin. Within 15 min at ambient temperature... 

Various polyesters derived from phosphorous or phosphoric acids were prepared. Efiicient polyphosphites were synthesised in the early 196(. Polyphosphite prepared from 152 and 4,4 -isopropylidenebis(cyclohexanol) was tested as a thermal stabilizer for PC [199] or as secondary AO for radiation sterilized EPM [200]. Built-in phosphites obtained by transesterification of triallcylphosphite with 4,4 -isopro-pylidenebisphenol or 4,4 -thiobisphenol possess antioxidant properties in polyolefins. Stabilizer containing phosphite moiety 153 was prepared from tris(2-hydroxy-ethyl)isocyanate, decyl alcohol and triphenylphosphite [201]. Various phosphites were derived firom polynuclear phenols or dihydric phenols. For example, a polycondensate prepared by reaction of phosphorus trichloride with 2,5-di-rert-butylhydroquinone was tested as heat and light stabilizer for PP [202], A linear polyester with a built-in phenolic moiety was synthesised from (2,6-di-tm-butyl-4-methylphenyl)bis(6-hydroxyhexyl)phosphite and dimethyl terephthalate [203]. 

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