Hindered amine stabilizers nitroxide derivation

Fig. 3. X-band ESR spectrum at 300 K of a nitroxide radical derived from Tinuvin 770, a hindered amine stabilizer, in heterophasic poly(acrylonitrile-butadiene-styrene) (ABS). Fast and slow components are indicated (see text).

Fig. 4. The ID ESRI at 340 K of a cylindrical sample (height 3 mm, diameter == 4 mm) of heterophasic propylene-ethylene copolymer (HPEC) containing a nitroxide derived from a hindered amine stabilizer (HAS). X-band ESR spectrum recorded in the absence (a) and in the presence of a vertical magnetic field gradient of 206 G cm b).

ESR Spectra of Nitroxides Derived from Hindered Amine Stabilizers in Aged... 

ESR SPECTRA OF NITROXIDES DERIVED FROM HINDERED AMINE STABILIZERS... 

Figure 23.6 (a) Two-dimensional (2D) spectral-spatial perspective plot of nitroxide biradicals derived from hindered amine stabilizer (HAS) doped in HPEC (copolymer of ethylene and propylene [39c,b]) on one side of the... 

Figure 12 Determination of concentration profiles in thermally treated HPEC containing a nitroxide derived from a hindered amine stabilizer (HAS).

Figure 14 presents the 2D spearal-spatial ESRI perspective plot and corresponding virtual slices for nitroxide radicals derived from hindered amine stabilizers (HASs) generated during the UVB irradiation of heterophasic propylene-ethylene copolymers (HPEC). " Note that the ESR spectra shown in the spectral slices consist of two spectral components, F and S, whose relative intensities vary as a function of sample depth, from about 22% near the irradiated side to about 45% at the other sample extremity. Data such as those shown in Figure 14... 

Hindered amine light stabilizers have attracted enormous scientific and commercial interest due to their efficiency as photo-antioxidants. The stabilization process in the presence of HALS involves the interference of secondary >NH or tertiary (>NCH3) groups with hydroperoxides POOH generated by oxidation chain mechanism of polymer alkyl radicals P. HALS-derived nitroxides >NO, formed through scavenging peroxyls POO by hydroxylamine species >NOH, are the key intermediates in the HALS stabilization mechanism because they are able to quench alkyl radicals arising in the initiation step of oxidation [100, 101]. The involvement of HALS in the stabilization process can be attributed to their ability to remain an... 

Attachment of B ansformation Products of Stabilizers. Up-to-date knowledge dealing with the chemistry of transformation products of phenolic [6, 15, 17, 20] and aromatic aminic [16, 43, 230] antioxidants and photoantioxidants based on hindered piperidines [10] indicates the possibility of attaching compounds having structures of quinone imine or quinone methide, or of radical species like cyclohexadienonyl, phenoxyl, aminyl or nitroxide to polymeric backbones. These reactions proceed mostly via reactivity of macroalkyl radicals derived fi-om stabilized polymers. Various compounds modelling this reactivity have been isolated [19, 230]. These results are of importance mainly for the explanation of mechanisms of antioxidant activity [6, 22, 24]. 

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