Лако-красочные материалы — производство

A. Synthesis and Characterization Within the forest products industry, polymeric MDI competes against the form­aldehyde based thermosets such as urea-formaldehyde, melamine-urea-formaldehyde, and phenol-formaldehyde. Interestingly, the isocyanate wood binders are also based upon formaldehyde. Their preparation begins with the HCl catalyzed condensation of form­aldehyde with aniline, as shown below [2,3]. The scheme above belies the complexity […]

Charles E. Frazier Virginia Polytechnic Institute and State University, Blacksburg, Virginia, U. S.A. I. INTRODUCTION Over the last thirty years, the forest products industry has increasingly embraced isocyanate wood binders. This trend is partly due to the tremendous growth of the world­wide polyurethane industry. Central to this growth has been the demand for the aromatic […]

Follow the same procedure as for formulation A, but at the end of the water vacuum distillation add 1.7 to 1.9 parts by mass of the second melamine and heat the reaction mixture to 95°C again and maintain this temperature for 5 to 6 min, then cool rapidly. B. MUF Formulation for Exterior Particleboard This […]

For starting experiments in MF resins, the following formulations are suggested. A. MF Formulation for Exterior Particleboard In a reaction vessel charge at 25°C, 44.4 parts by mass of water, add 30% NaOH solution to pH 11.2 to 12.0, followed by 15.5 parts of 91% paraformaldehyde prills, 34.4 parts of melamine powder, 2.8 parts of […]

The analysis of these resins is difficult when unknown products, particularly fully cured have to be tested for UF and MF resins. Widmer [50] offers a method for the identification of UF and MF resins in technical products. This involves preparing crystalline products of urea and melamine and identifying them under the microscope. Melamine (in […]

MUF resin can be used as a cold-setting wood laminating adhesive for glulam and fin­gerjointing by the use of adequate acid hardeners. In all semiexterior and protected exter­ior structural applications where a clear/invisible glue line is preferred for aesthetic reasons then a MUF adhesive is preferred to the classical PRF adhesives used for this purpose. […]

Temperature-time-transformation (TTT) and continuous-heating-transformation (CHT) curing diagrams for polycondensation resins are starting to acquire more importance in the deductions of the behavior of different resins during hardening. They are a type of state diagram. TTT and CHT diagrams of resins by themselves or on noninteracting substrates show similar trends as exemplified by the case of […]

Several effective techniques to consistently and markedly decrease the melamine content in MUF wood adhesives without any loss of performance have also been recently developed. Some of these formulation systems and techniques are already in the early stages of industrialization. Among these melamine/acid salts, such as melamine acetate (Formula 5), function both as efficient hidden […]

Because of their characteristic rigidity and brittleness in their cured state, when MF resins are used for impregnated paper overlays, small amounts (typically 3 to 5%) of modifying compounds are often copolymerized with the MF resin during its preparation to give better flexibility to the finished product and better viscoelastic dissipation of stress in the […]

With regard to melamine-urea-formaldehyde, copolymers can be prepared which are generally used to cheapen the cost of MF resins, but which also show some worsening of properties. Copolymerization was proven by means of model compounds and poly­condensates [9]. MUF resins obtained by copolymerization during the resin preparation stage are superior in performance to MUF resins […]