Determination of melamine contents in urea-melamine resins by infrared spectroscopy

Urea-melamine resins are widely used as wood adhesives. The infrared spectral method for the determination of melamine contents in urea-melamine resins was studied. The KBr-tablet method was satisfactory for this purpose, and potassium thiocyanate was most suitable for the internal standard. It was found that the ratio of the optical density at the wavenumber 810cm-1, X (melamine), to the optical density at 2050 cm-1, Y (KSCN), of the spectrum was proportional to the ratio of melamine to KSCN. A calibration curve was constructed for the relation between X/Y and melamine/KSCN by the standard mixtures. The reproducibility and recovery test of this method was examined on the standard samples prepared by different processes. The standard deviation of this method was below 0.5% as melamine content. This method is suitable for routine analysis because of its accuracy, simplicity, and rapidity.