Modern methods for the analysis of urea formaldehyde resins

Abstract

Modern instrumental techniques were used for analysing water-based urea-formaldehyde resins. An exhaustive study was made of the silylation of such a resin with BSTFA (N,O-bistrimethylsilyltrifluoroacetamide). From the gas chromatograms the amounts of urea, monomethylol urea and dimethylol urea can be determined quantitatively, thus giving information on the low molecular weight part of the resin. The ratio of low to high molecular weight components as well as the amounts of several low molecular weight compounds can be estimated from a GPC analysis on Sephadex LH 20 in water. A detailed picture of the resin is obtained when freeze-dried samples are subjected to 220 MHz 'H-NMR analysis in DMSO-d6.An overall insight into the composition of these resins can be gained when the results of the mentioned techniques are combined with those of classical chemical analyses. ZUSAMMENFASSUNG: Moderne instrumentelle Methoden wurden zur Analyse von Harnstoff-Formaldehyd-Harzen verwendet. Ein ausfuhrliches Studium der Silylierung des Harzes mittels BSTFA (N,O-Bistrimethylsilyltrifluoracetamid) ermoglicht die quantitative gaschromatographische Bestimmung der niedermolekularen Verbindungen Harnstoff, Monomethylolharnstoff und Dimethylolharnstoff. Das Verhaltnis zwischen nieder-und hochmolekularen Verbindungen sowie die Mengen an niedermolekularen Verbindungen konnen mittels GPC-Analyse auf Sephadex LH 20 in Wasser ermittelt werden.Ein vollstandiges Bild des Harzes erhalt man durch 220 MHz 'H-NMR-Analyse von Losungen von gefriergetrockneten Proben in DMSO-d6. Zusammen mit den Ergebnissen klassischer chemischer Analysen ergeben die Resultate der drei genannten Techniken einen guten Uberblick iiber den Aufbau eines Harnstoff-Formaldehyd-Harzes.

Proton and carbon-13 nuclear magnetic resonance spectrometry of formaldehyde in water

“…(10) Iyengar, G. V.; Kasperek, K.; Felndegen, L. E. Scl. A number of NMR studies, involving either 1H or 13C spectrometry, have been devoted to aqueous solutions of formaldehyde owing to the great industrial importance of this compound (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). In aqueous solutions, formaldehyde reacts with water to give methylene glycol which oligomerizes easily according to the following scheme: CH20 + H20 Fi hoch2oh HOCH2OH + HOCH2OH H0(CH20)2H + h2o HO(CH20)n-1H + HOCH2OH HO(CH20)"H + H20…”

“…The structures of the different species present in the solutions have already been determined, mainly by NMR (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), but no special attention has been paid to the influence of temperature on the oligomeric distribution nor to the chemical relaxation rate of dilution, i.e., the time required for the solution to reach equilibrium when the concentration is changed. On the other hand, the quantitative determination of oligomers in solutions, which is performed by gas chromatography (GC), necessitates the substitution of the labile hydrogens by a trimethylsilyl group, and one might expect the distribution measured by GC to be perturbed by this chemical treatment.…”

Quantitative and qualitative 1H, 13C, and 15N NMR spectroscopic investigation of the urea–formaldehyde resin synthesis

“… Other early analyses of the system by 13 C NMR spectroscopy provide qualitative information only. Tomita reported the first quantitative analysis of finished resins by 13 C NMR spectroscopy, followed by Rammon et al . and Kim.…”

Study on Curing Characteristics of Low-Toxicity Urea-Formaldehyde Resin

“…UF resin adhesive was a heterogeneous system. Reaction activity energy of UF resin adhesive under the different curing system was found by Piloyan-Ryabchihov-Novikova-Maycock method [6][7]. ); R -universal gas constant, 8.314J/( K mol ); T -absolute temperature( K ).…”