of condensation and structure of melamine-formaldehyde resins
Several analytical methods were used for the determination of the chemical mechanism of condensation of melamine with formaldehyde at molar ratio of melamine to formaldehyde in the range of 1 : 2.4 to 3.0. The effect of time of condensation and pH-value of the reaction medium was investigated. The content of methylol groups, dimethyleneether bridges and free formaldehyde was determined. To determine the chemical structure of melamine-formaldehyde resins prepared under selected conditions of condensation and at a molar ratio of formaldehyde to melamine 1 : 3.0 13C-NMR spectra and mass spectroscopy spectra were determined and evaluated. Molecular weights and molecular weight distribution of the resins were determined by the GPC-method. The results of these investigations were applied in the development of a liquid adhesive composition for the manufacture of water-resistant plywood and chipboard.
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