Synthesis and characterization of phenolic and amino resins based on α, β‐unsaturated aldehydes

Abstract

AbstractPhenolic and amino resins on the basis of α,β‐unsaturated aldehydes were synthesized in bulk or solution. Catalysts were HCl, H3PO4, or formic acid, and in some cases NaOH. The course of the reactions was followed by GPC and NMR while the structure of the reaction products was determined by one‐ and two‐dimensional NMR. The course of the reactions is influenced by experimental conditions: the type of monomers, their molar ratio, the type and quantity of the catalyst, the reaction time and temperature, and the reaction medium. At the beginning of the reaction the addition of a nucleophile to an aldehyde takes place through parallel 1,2‐addition to and 1,4‐addition to group. Oligomers with OH, , and CHO functional groups are able to add new monomer units or to react mutually to form higher molecular weight addition and condensation products. The overall rate constants for the beginning of the reactions were between 10−3 L/mol s for the high reactive mixtures and 10−7 L/mol s for the less reactive mixtures. The resins were cured by heating at temperatures above 135°C with the addition of hexamethylenetetramine.