I. Slonim, S. G. Alekseyeva, Ya. G. Urman
1977
Citations
0
Influential Citations
12
Citations
Journal
Polymer Science U.s.s.r.
Abstract
Abstract A 13 C-NMR method has been developed for the determination of the structure of urea-formaldehyde resins. The signals have been identified on the basis of spectra produced from a number of model compounds, and the dependence of the spectra on the urea formaldehyde components ratio, but also from the duration of the reaction. The signals are those of the methylene and methylate linkages in the linear chain, while they are those of the methoxymethylene groups, the radicals of tetra-, tri-, di- and mono-substituted urea, and of free urea, free methanol, and free formaldehyde (methylene glycol and polyoxymethlyene glycol oligomers) in the branches. Branches will form in the early stages of condensation under industrial scale production conditions when the urea: formaldehyde ratio is from 1 : 2 to 1 : 1·3, and the pH = 4·5−8·5, and the products will have a linear-branched structure.