Melamine-formaldehyde resins resinification

Further heating causes condensation into resins. The rate of such resinifications is pH-dependent. Melamine-formaldehyde resins are also etherified for solvent solubility. Methanol is often used and hexamethyl ether of hexamethylolmelamine as well as higher homologues are available commercially. The hexamethyl ether can be shown as follows ... 

On further heating, the methylol melamines undergo condensation reactions, and a point is reached where hydrophobic resin separates out. The rate of resinification depends on pH. The rate is minimum at about pH 10.0-10.5 and increases considerably both at lower and higher pH. The mechanism of resinification and cross-linking is similar to that observed for urea-formaldehyde (Figure 4.26) and involves methylol-amine and methylol-methylol condensations. 

---