Carbon-13 CP/MAS NMR study of the structural dependence of urea-formaldehyde resins on formaldehyde-to-urea molar ratios at different urea concentrations and pH values

摘要: Urea-formaldehyde (UF) resins prepared at room temperature from reaction mixtures with four different formaldehyde-to-urea molar ratios (1.00, 1.50, 2.00, and 3.00), three urea concentrations, six pH values (1,3,5,7,9, 12) were investigated. The quantitation aspect of obtaining 13 C CP/MAS NMR spectra spinning rates about 6.5 kHz was examined. under acidic conditions range a very simple structure to complicated ones, the details depending on concentration, value F/U ratio