Additives amine antioxidants

Although spironaphthooxazines have excellent lightfastness, they decompose slowly on exposure to sunlight. However, lightfastness can be improved by addition of nickel stabilizers (singlet oxygen quenchers) or hindered amines (antioxidants).86 88... 

Fluorescence is much more widely used for analysis than phosphorescence. Yet, the use of fluorescent detectors is limited to the restricted set of additives with fluorescent properties. Fluorescence detection is highly recommended for food analysis (e.g. vitamins), bioscience applications, and environmental analysis. As to poly-mer/additive analysis fluorescence and phosphorescence analysis of UV absorbers, optical brighteners, phenolic and aromatic amine antioxidants are most recurrent [25] with an extensive listing for 29 UVAs and AOs in an organic solvent medium at r.t. and 77 K by Kirkbright et al. [149]. 

There have been some examples of the use of LDMS applied to the analysis of compounds separated via TLC, although not specifically dealing with polymer additives [852]. Dewey and Finney [838] have described direct TLC-spectroscopy and TLC-LMMS as applied to the analysis of lubricating oil additives (phenolic and amine antioxidants, detergents, dispersants, viscosity index improvers, corrosion inhibitors and metal deactivators). Also a series of general organics and ionic surfactants were analysed by means of direct normal-phase HPTLC-LMMS [837]. Novak and Hercules [858] have... 

The initial step of both the above reactions, the formation of an acyl radical, is catalysed by light and by metal ions that are capable of a one-electron reduction transition (e.g. Fe3+ -+ Fe2 + ). Thus, the autoxida-tion of aldehydes can be greatly slowed by keeping the compounds in the dark and by very careful purification. Flowever, the most efficient method is the addition of antioxidants, such as phenols and aromatic amines, which react preferentially with any radicals that may be present. 

Naugalube . [Umroyal] Alkylated secondary aromatic amine antioxidant for automatic transmissitm fluids, turbine oils, synthetic jet turbine lubricants petroleum additives. 

Many elastomers are subject to oxidative degradation and can be protected to some extent by the addition of antioxidants, such as amines and hydroquinones. 

Volatility As a rule, the higher the molecular weight of the antioxidant, the less volatile it will be, though hindered phenols tend to be highly volatile compared with amines of equivalent molecular weight. Thus, correct addition of antioxidants in the compound mix cycle is critical if loss of material is to be avoided. 

In addition to the use of the above phenolic and amine type antioxidants, peroxide decomposers are used to harmlessly decompose the peroxides, which otherwise could decompose to give free radical propagating species, e.g., R-0 or H-0 . Examples of such peroxide decomposers, which act synergisticaUy with the phenolic or amine antioxidants, are dilauryl- 3, 3-thiodiproprionate and tris(p-nonylphenyl)phosphite. These and others are also listed in Table 4.10, with their chemical structures being listed in Table 4.11. We note that some of the peroxide decomposers are also accelerators for sulfur vulcanization. 

A very popular method of estimating antioxidants in polymer extracts is by coupling or oxidising them to form coloured products and measuring the resulting absorbance in the visible region of the spectrum. This technique is not particularly specific for individual antioxidants, but is specific for phenolic antioxidants in general (also amine antioxidants), and hence can often be applied without interference from other types of polymer additives. 

Thermooxidative degradation, which is more of a problem with polyether polyurethanes, can be inhibited by the addition of antioxidants. Mathur et al. have studied the effectiveness of several commercial antioxidants for stabilizing polyether polyurethanes against UV and thermally induced oxidation. Stabilizers against thermooxidation include hindered phenols, aromatic amines, and phosphites. Commercially available antioxidants have recently been reviewed by Allbee. Replacement of some, or all, of the ether linkages in polyether polyurethanes by silicone has led to a marked improvement in the thermooxidative stability of the resulting polymer. " ... 

Many modern plastics and rubbers are stabilized with synergistic mixtures of a phenolic, or amine antioxidant in combination with a thiodipropionate ester or a phosphite. Such mixtures typically achieve stability very much greater than could be obtained from either additive used alone. For example a mixture of a phenolic antioxidant with a phosphite is currently the state-of-the-art formulation for melt stabilization of polypropylene. 

These relatively new techniques viz laser desorption/ionization Fourier transform mass spectrometry and fast atom bombardment and laser desorption Fourier transform ion cyclotron resonance mass spectrometry have been applied to the determination of non volatile polymer additives (thioester, phosphite, phosphonate and hindered amine antioxidant types) and antioxidants, ultraviolet absorbers and amide waxes. 

This thin-layer method is capable of determining a wide range of polymer additives, viz amine antioxidants, uv absorbers and organotin stabilizers in amounts down to 0.02% in polyalkenes. 

Antioxidants. All nitrile rubber producers add an antioxidant to their raw nitrile rubbers. However, where heat resistance and the maximum in durability and service is demanded, additional antioxidant may be added to the cement. Antioxidants commonly used in nitrile rubbers (e.g., amine antioxidants) may be used if staining is not a factor. Antioxidants may also contribute stability and tack. 

Hindered amine antioxidants, as shown below, undergo the same two basic reactions as their fellow radical trapping phenolic counterparts. In addition, the amines can enter into a cyclic process to continuously trap radicals without being consumed. This can yield a longer lifetime at elevated temperature. 

It was surmised that the main differences in the types of failures observed and the non-failed samples was the duration in service and the varying service conditions (temperature, pH and chlorine content of the water). An early response to the failures was to create an enhanced version of the new formula with increased levels of the secondary antioxidants in the formulation. As time passed, it was evident that the additional secondary antioxidants had little effect on the failure rate of the parts and the manufacturer switched back to the original formula. Later an enhanced original formula was used, with increased levels of the primary hindered amine antioxidant. 

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