Antiozonant mechanisms product studies

Products Studies in Antiozonant Mechanisms. Experimental proof of the individual antiozonant theories based on product studies are scarce. Using a very sophisticated instrumental analytical approach, the composition of a very complicated mixture of ozonation products of two technically important antiozonants, i.e., DOPPD and HPPD has been revealed and the reactivity pathways with ozone have been established (24, 40). Influence of the character of N-substituents on the ozonation mechanism has been evidenced. Some important... 

This mechanism is based on the fact that the ozone uptake of elongated rubber containing a substituted p-phenylene diamine type of antiozonant is very fast initially and then decreases rather rapidly with time and eventually stops almost completely. The film has been studied spectroscopically and shown to consist of unreacted antiozonant and its ozonized products, but no ozonized rubber is involved [64], Since these ozonized products are polar, they have poor solubility in the rubber and accumulate on the surface. 

The ozone concentration in the troposphere during the daytime is typically about 1 pphm (parts per hundred million parts of air by volume) [20], Values up to 100 pphm were measured in some photochemical smog areas. The molecular mechanism of the ozone aging of diene based elastomers was studied in detail and is well understood [19,21], Products or intermediates different from those arising in autoxidation or photo-oxidation of polymers were identified ozonides (3), zwitterions (4), diperoxides (5), polyperoxides (6), polymeric ozonides (7) and terminal aldehydes (8). Reactivity of aminic antiozonants (AOZ) with these species accounts for the protection of rubbers against atmospheric 03. AOZ must also possess antioxidant properties, because the free radical processes are concerted with ozonation due to the permanent presence of oxygen. 

The mechanism of the antiozonant protection has been the matter of studies and discussions for a long time [3,4,18,21,31] and it is still an area of active research. Due to the diversity of the deteriogens and reactive products of rubber degradation involved in ozone ageing, more concerted protective mechanisms are certainly included [247], The antiozonant activity accounts for a combination of a direct scavenging of ozone by the chemical AOZ and formation of... 

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