Amino resins used in the production of wood-derived materials. Part II. Investigations of the stability
The MMF resins were obtained either by mixing non-distilled melamine resins with distilled urea resins or by concentrating melamine and urea resins together. Several weight ratios of the component resins were used. Melamine resins with a molar ratio of melamine to formaldehyde as 1:3 were condensed by classical method, and urea resins were condensed in a few-step process in several molar ratios. The ontent of methylol groups, dimethylene ether bridges and free formaldehyde was determined. Chemical structure of MMF resins was determined by the 13C-NMR and mass spectroscopy methods. Molecular weights and molecular weight distribution of MMF resins were determined by the GPC method. The stability at room temperature of MMF resins differing in manufacturing method and composition was also determined. The results of these investigation were applied in the development of a liquid adhesive composition for manufacture of mushroom-, fire-, and water-resistant chipboard and plywood.
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