Hindered phenol, inhibition

Radical Scavengers Hydrogen-donating antioxidants (AH), such as hindered phenols and secondary aromatic amines, inhibit oxidation by competing with the organic substrate (RH) for peroxy radicals. This shortens the kinetic chain length of the propagation reactions. 

New developments are hydroxylamines and lactones (for processing stability), which operate at an earlier stage during stabilisation. Lactone (benzofuranone) chemistry has been identified as commercially viable, and marks a revolutionary advance in comparison to hindered phenols and phosphites [18]. New lactone chemistry (Figure 10.1) provides enhanced additive compatibility, reduced taste and odour (organoleptics), resistance to irradiation-induced oxidation, and inhibition of gas fade discoloration. The commercial introduction of fundamentally new types of stabilisers for commodity and engineering polymers is not expected in the near future. 

VA Roginskii. Oxidation of polyolefines inhibited by sterically hindered phenols, Doctoral Thesis Dissertation, Institute of Chemical Physics, Chernogolovka, 1983. 

Perform as an effective substitute for a hindered phenol or phenylenediamine antioxidant in inhibiting free radical reactions in gasoline or jet fuel. 

Chemical compound or substance that inhibits oxidation, decomposes peroxides and terminates free radicals, eg., ZDDP, hindered phenols, aromatic amines. 

Synergism between Hindered Phenolics and DLTDP in Polypropylene Formulations. When polypropylene is inhibited separately either... 

The degradation of polymers is mostly promoted by autoxidation. The propagation of autoxidation can be inhibited by antioxidants (e.g. hindered phenols and amines). 

Perevozkina M.G., Storozhok N.M., Nikiforov G.A., Correlation between chemical structure and inhibiting properties of sterically-hindered phenols of the ichfan group, Biomed. khim., 2005, vol. 51, pp. 413-423. (in Russian). 

Figure 1.42. Weight loss from polyacetal during processing due to liberation of formaldehyde and inhibition by an acid scavenger combined with a hindered phenol antioxidant. Adapted from Zweifel (1998).

Inhibition of oxidation occurs by the prevention of chain propagation. Equation (3.2) (ii) or (iii). Hindered phenols and aromatic amines donate a hydrogen atom to the peroxy radical, ROO, Reaction (3.3), in successful competition with Reaction (3.2(iii)) ... 

An alternative reaction mechanism to Reactions (4.31) and (4.32) has been suggested concerning how sterically hindered phenols act as antioxidants for lubricants [27]. Based on the fate of 2,6-di-ferft fl/7-butyl-p-cresol in a turbine oil used in a conventional steam turbine, it was concluded that there is a strong possibility that this phenol is consumed not through the inhibition of oxidation, Reactions (4.31) and (4.32), but via direct oxidation with oxygen. Reaction sequence (4.33) ... 

It is thus apparent that selected antioxidants, AH, in the present case hindered phenolics, and hydroperoxide decomposers, such as PR", act synergistically to inhibit radical initiated polymer-chain oxidations. 

The solution oxidation technique allows the study of polyolefin autoxi-dation under conditions where the temperature, concentration of reactants, and rates of radical initiation can be controlled. The results should be considered as a useful prelude to any fundamental understanding of the autoxidation processes which occur in neat polymers where the effects of very high viscosity, partial crystallinity, and oxygen diffusion rates are included. The objective of our work was to determine the kinetics and stoichiometry of the inhibited autoxidation of polypropylene in solution. A relatively detailed study of the oxidation of polypropylene inhibited by 2,6-di-terf-butyl-4-methylphenol [butylated hydroxytoluene (BHT)] has been made for comparison with data obtained in polypropylene oxidations inhibited by a variety of other stabilizers which include commercial polyfunctional antioxidants. Singly hindered phenols appeared to be superior in the inhibited-solution oxidation of polypropylene, and the application of this finding to stabilization technology was investigated briefly. 

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