Resistance of Cured Urea-Formaldehyde Resins to Hydrolysis: A Method of Evaluation

Abstract

A new method for measuring formaldehyde released from cured urea formaldehyde resins under conditions favouring hydrolysis is described. The technique is devised for both industrial quality control and research and it is relatively fast, permits the independent control of water activity and temperature and guarantees the absence of leaching of resin ingredients. The aim of verifying the suitability of the method was persuaded through studying the effect of F: U molar ratio, type of UF concentrate, manufacturing technology, type and concentration of catalyst, type of formaldehyde-scavenging and acid-neutralising additives, on the hydrolytic stability of cured urea-formaldehyde resins. The fact that qualitatively similar results have been reported by other researchers using the Flask method, or versions of the WKI method confirms the reliability of the new technique.

Influence of acrylamide copolymerization of urea–formaldehyde resin adhesives to their chemical structure and performance

“…10 As a way of understanding of the formaldehyde emissions of amino resins, many studies attempted to measure hydrolytic stability of amino resin adhesives (UF resin or MUF resin). 5,[10][11][12] These studies suggested that the hydrolysis of UF resin consisted of different reversible reactions to those of the UF resin synthesis. For example, infrared spectra study showed major reduction of the content of methylol groups (CH 2 OH) while it increased tertiary amide.…”

Wood production, wood technology, and biotechnological impacts

“…Currently used UFRs mixtures keep with molar U/F ratios of 1:1.05 to 1:1.1 in the tolerated limits have however the disadvantages of a lower potential for dilution with water and of a longer curing time. Furthermore, the produced panel boards have a lower water resistance because the resins are more vulnerable to hydrolysis (Pizzi & Mittal 1994, Dunky 1998, Kavvouras et al 1998, Vargha 1998, Mansouri & Pizzi 2006.…”

Effect of γ-irradiation on the hydrolytic stability and thermo-oxidative behavior of bio/inorganic modified urea–formaldehyde resins

“…The emitted formaldehyde causes from a free formaldehyde present in UF resins after synthesis and mostly from hydrolysis of UF resins under acidic and moisture conditions. Many studies have recognized the hydrolysis as a responsible factor in long-term formaldehyde emission of UF resin bonded wood panels [6][7][8][9][10]. Hence, the efforts were directed to the better understanding of resin hydrolytic degradation process and ways of minimization of the formaldehyde emission.…”