Лако-красочные материалы — производство

The various components and raw materials of the resins can be determined using different chemical methods (Table 19). The content of total formaldehyde is accessible by hydrolysis of an aminoplastic resin; this process, however, is not possible for PF resins. Urea can be determined in the easiest way from the resin nitrogen content. However, other […]

The properties of a resin which can be determined by simple test methods are shown in Table 18. The solids content of a resin usually is determined by the so-called dish method at 120°C for 2h [different times and sometimes lower temperatures (105°C) are often used as several variations of this method exist]. Even if […]

There has been considerable progress in the characterization of formaldehyde condensa­tion resins in the past two decades. It is now possible to analyze the polydisperse nature of the resins as well as the individual structural elements in the resins, even semi quantita­tively. The curing reaction can also be monitored by means of adequate methods. The […]

In the production of particleboards and MDF only liquid resins are used. In OSB produc­tion in Europe liquid resins are more often used, while rather in North America powder resins are used. The advantages and disadvantages of liquid and powder resins are sum­marized in Table 16. A. Combination of Various Adhesives For the purpose of […]

The objective of the development of adhesive resins is to achieve as high reactivities as possible, while maintaining within acceptable limits other properties such as the storage stability of the resin or the pot life of the glue mix. The reactivities of the resin and of the glue mix are determined by various parameters: type […]

Aqueous adhesive resins behave similarly to water regarding surface tension and wetting behavior. For UF resins the wetting behavior strongly depends on their molecular composition [24]. The higher the F/U molar ratio the lower the surface tension, which also can be decreased by adding a detergent [24] (a practice well known in other wood adhe­sives […]

The flowability of a resin depends on its viscosity and the solids content as well as the changes in the viscosity at elevated temperatures in the hardening glue line. A low flow — ability causes poor penetration of the resin into the wood surface and low bonding strengths. A too high flowability, on the other […]

The viscosity of a glue mix is determined by the viscosity of the resin (mainly depending on the degree of condensation and the resin solids content) and the composition of the glue mix. If the viscosity or the degree of condensation of the resin is too low, a large portion of the resin might penetrate […]

For the production of wood-based panels various adhesives are in use, including aminoplastic resins (UF, MUF, MUPF), phenolic resins (PF), and isocyanate (PMDI). Table 15 Evaluation of the Three Adhesive Types UF, PF, and PMDI with Regard to Various Parameters Property UF PF PMDI Price low medium high Necessary hardening temperature low high low Susceptibility […]

Poly(vinyl acetate) (PVAc) adhesives are another important type of thermoplastic adhe­sive, especially in furniture manufacturing and carpentry. They form the bondline in a physical process by losing their water content to the two wooden adherends. PVAc adhe­sives are ready to use, have a short setting time, and give flexible and invisible joints. They are easy […]