Antioxidants hindered phenolic

Plasticiser/oil in rubber is usually determined by solvent extraction (ISO 1407) and FTIR identification [57] TGA can usually provide good quantifications of plasticiser contents. Antidegradants in rubber compounds may be determined by HS-GC-MS for volatile species (e.g. BHT, IPPD), but usually solvent extraction is required, followed by GC-MS, HPLC, UV or DP-MS analysis. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out. The determination of antioxidants in rubbers by means of HPLC and TLC has been reviewed [58], The TLC technique for antidegradants in rubbers is described in ASTM D 3156 and ISO 4645.2 (1984). Direct probe EIMS was also used to analyse antioxidants (hindered phenols and aromatic amines) in rubber extracts [59]. ISO 11089 (1997) deals with the determination of /V-phenyl-/9-naphthylamine and poly-2,2,4-trimethyl-1,2-dihydroquinoline (TMDQ) as well as other generic types of antiozonants such as IV-alkyl-AL-phenyl-p-phenylenediamines (e.g. IPPD and 6PPD) and A-aryl-AL-aryl-p-phenylenediamines (e.g. DPPD), by means of HPLC. 

FD-MS is also an effective analytical method for direct analysis of many rubber and plastic additives. Lattimer and Welch [113,114] showed that FD-MS gives excellent molecular ion spectra for a variety of polymer additives, including rubber accelerators (dithiocar-bamates, guanidines, benzothiazyl, and thiuram derivatives), antioxidants (hindered phenols, aromatic amines), p-phcnylenediamine-based antiozonants, processing oils and phthalate plasticisers. Alkylphenol ethoxylate surfactants have been characterised by FD-MS [115]. Jack-son et al. [116] analysed some plastic additives (hindered phenol AOs and benzotriazole UVA) by FD-MS. Reaction products of a p-phenylenediaminc antiozonant and d.v-9-lricoscnc (a model olefin) were assessed by FD-MS [117],... 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

Cyanox 1790 Antioxidant (hindered phenol) American Cyanamide Co. 1,3,5-Tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-s-triazine-2,4,6(1R,3R,5E)-trione... 

Pospfsil J (1998) Antioxidants hindered phenols, In Plastics additives, an A-Z reference, Pritchard G (Ed), Chapman Hall London, pp 72-79. 

Antioxidants. Hindered phenol antioxidants such as 2,6-ditertiary butyl-4-methylphenol (BHT) controls the exotherm in the reaction between diol and diisocyanate. When acidic flame retardants are present in the formulation, amine antioxidants are preferred (Seymour, 1992). 

Utilizing a voltammetric measurement technique, the RULER quantitatively analyses the relative concentrations of antioxidants (hindered phenolic and aromatic amine) in new and used oils. This data can be trended to determine the depletion rates of the antioxidant protection package in the oil provided the instrument has been calibrated for that oil type. From pre-established limits, proper oil change cycles, potential interval extension or timely antioxidant replenishments can be determined. 

The very reactive radicals R are blocked by being transformed into a neutral molecule (RH) and a radical of very low reactivity stabilised by conjugation. In that way the chain reactions are interrupted. Both antioxidants (hindered phenols and diphenylamines) are consumed after hydrogen radical donation (sacrificial antioxidants) [140]. 

Costabilzers enhancing light stability HALS light stabilizers, antioxidants (hindered phenols, phosphites, thiosyn-ergists, hydroxylamines, lactones) ... 

Costabilizers enhancing light stability can be used in combination with functional additives such as antioxidant (hindered phenols, phosphites) and HALS ... 

See also Antioxidants hindered phenols Antioxidants for polyfethylene terephthalate) ... 

Alvinox P is utilized to protect polymers from thermal oxidation particularly during processing. It acts essentially as a decomposer of hydroperoxides. Optimum performance is obtained when the product is used in combination with antioxidants (hindered phenols and/or thioethers) which additionally protect the polymer against long-term heat degradation. 

OIT/Tox measurements provide rapid and reliable results. Many materials contain a system of antioxidants, often a combination of a primary antioxidant (hindered phenol or amine) and a secondary antioxidant (phosphite, thioester, etc.). Thermal analysis provides no information about the concentration of the different antioxidants separately but rather an overall assessment of the stability. Extraction followed by chromatography (HPLC) is one of the main techniques for the determination of antioxidant concentration, but it is no doubt much more time-consuming than DSC/DTA. 

Among the abundance of tested classes of substances, PCA is the only additive reliably protecting PSF from oxidation in concentrations below 0.3 wt.%. As expected, by analogy with polycarbonate and other heterochain polymers processed at temperatures about 300°C, classical primary antioxidants (hindered phenols and aromatic amines) are at most neutral (amines catastrophically color PSF), which proved existence of the effective inhibition temperature limit (120 - 125°C) [11, p. 218]. It is stipulated by activity of phenoxyl radicals in reactions with hydroperoxides. Commonly, all so-called non-chain inhibitors intensify... 

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