Hardeners phenolic Mannich bases

In connection with this special interest present phenolic Mannich bases (PMBs) due to two types of reactive groups, such as phenolic hydroxyl and amine, connected with intermolecular hydrogen bonds. Depending on their amino groups, PMBs can be used as hardeners for cold and hot curing. 

As modifiers, low molecular weight rubbers with carboxyl terminal reactive groups are more effective. As hardeners, we recommend phenolic Mannich bases, such as dimethylaminomethyl phenols for hot curing and ethylene di aminomethyl phenols for cold curing. 

Other modifications of the polyamines include limited addition of alkylene oxide to yield the corresponding hydroxyalkyl derivatives (225) and cyanoethylation of DETA or TETA, usuaHy by reaction with acrylonitrile [107-13-1/, to give derivatives providing longer pot Hfe and better wetting of glass (226). Also included are ketimines, made by the reaction of EDA with acetone for example. These derivatives can also be hydrogenated, as in the case of the equimolar adducts of DETA and methyl isobutyl ketone [108-10-1] or methyl isoamyl ketone [110-12-3] (221 or used as is to provide moisture cure performance. Mannich bases prepared from a phenol, formaldehyde and a polyamine are also used, such as the hardener prepared from cresol, DETA, and formaldehyde (228). Other modifications of polyamines for use as epoxy hardeners include reaction with aldehydes (229), epoxidized fatty nitriles (230), aromatic monoisocyanates (231), or propylene sulfide [1072-43-1] (232). 

Mannich base hardeners for curing epoxy resins may contain residual formaldehyde, phenol and benzyl alcohol, that can have undesirable effects when present in the final product. Determination of these compounds in the hardener was carried out by GC-FID of a 2% solution in chloroform-EtOH, using amyl alcohol as internal standard. LOD was 18, 30 and 26 ppm and LOQ was 75, 86 and 79 ppm of formaldehyde, phenol and benzyl alcohol, respectively. ... 

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