Phenol-aldehyde condensations stability

Among the polymeric stabilizers may be listed poly-condensed polymers based on alkyl phenols, aldehydes, and ketones of the aliphatic series, where = 1 - 8 and R,R means alkyl [24], Na, K, Ca phenolates of poly-condensed polymers [25], and also products of epichlor-ide with one or more aliphatic amines C3—C30 [26]. 

As has been indicated in a number of studies, sulfur-containing compounds give a synergic effect with amines and phenols in the stabilization of high-molecular compounds [89, 279]. The following have been proposed and are used as stabilizers of polyvinyl chloride mercaptides of antimony [280, 281], condensation products of aldehydes or ketones with mercaptans [63], thioesters [282], salts of thioacids [283], aromatic esters of aliphatic sulfonic acids [284], esters of xanthic acids [285] the use of the polysulfide of the composition... 

The acid condensation reaction of the aromatic and phenolic units is a typical reaction of lignin. The presence of acids results in resonance stabilized carbonium ion structures formed in the lignin macromolecule. These car-bonium ion structures react further, e.g., with unsubstituted positions in the lignin macromolecule. Thus, thermal treatment of powdered wood in acidic conditions causes condensation, the coniferyl aldehyde and coniferyl alcohol groups being especially reactive. In addition, other inter- and/or intramolecular condensations may occur. 

Antioxidants inhibit oxidation and are usually employed in combination with UV absorbers. Most antioxidants used for urethane coatings fall into the following classes substituted phenols, aromatic amines, condensation products of aminophenols with aldehydes, thio compounds, and phosphites. Often combinations of antioxidants from the above categories exhibit a synergistic effect. More recently Mathur et al. (125) carried out an extensive study involving the use of one to six stabilizers, selected from the above antioxidants and UV stabilizers, employing several independent test methods, to study the thermooxidation of urethane and urethane-urea films. 

Condensation products of amines and phenols with aldehydes and ketones are used as stabilizers. 

In contrast to thermal degradation, the mechanical properties decrease even before the material discolors. Condensation products of amines and phenols with aldehydes and ketones are added as stabilizers. 

---