Лако-красочные материалы — производство

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 main topics of analysis are: curing reaction and building up of bonding strength; evalua-

tion and monitoring of the degree of condensation and the molar mass distribution; analysis of the chemical composition of the resins and of their structural components.

The characterization of formaldehyde condensation resins was for several decades only possible with basic chemical methods, including elemental analysis [339]. The appli­cation of modern spectroscopic and chromatographic methods started as late as the 1970s. One of the reasons for this delay certainly is the fact that condensation resins themselves are still systems that might change during their preparation for analysis or during the analysis itself. Furthermore, the resins’ polar character as well as their relatively low solubility often render their analysis problematic. Notwithstanding this, the chemical and structural composition of condensation resins is today well known. The validity of each analytical method (Table 17) can be compared and correlated with the information derived from the resins’ technological behavior and from the properties of the wood panels bonded using these resins.

Table 17 Overview of Various Analysis Methods for Formaldehyde Condensation Adhesive Resins