Comparative Study of Synthesis Procedures for Urea - Formaldehyde Resins (Part I)
Journal Title: Leonardo Electronic Journal of Practices and Technologies - Year 2006, Vol 5, Issue 9
Abstract
This paper presents initial results from modifying the conventional synthesis procedure of UF resins, that is reacting urea and formaldehyde first in alkaline medium and subsequently in mild acid medium at reflux (conventional two - stage alkaline - acid synthesis), by conducting the reaction only in purely acid medium at 50oC (modified one - stage acid synthesis). In another attempt, the reaction was carried out in a neutral environment and at atmospheric temperature (modified one - stage neutral synthesis). The structural analysis of the various UF resin samples was carried out. The results showed that the UF resins (II) synthesized in acidic media, particularly that of pH 1.0, showed features in their spectra which are consistent with a tri -, and/or tetra - substituted urea in the reaction to give a 3 - dimensional network UF resin. A 3 - dimensional network resin is characterized by little or no hydroxyl groups with increased cross-link-density and hydrophobicity and hence improved hydrolytic stability. For the resin (III) obtained from the conventional method, the only clear distinction between spectra for the resins (II) synthesized in acid media is the presence of diminished peaks for methylene groups at 2.2 ppm. The resins (I) synthesized in neutral medium exhibited almost the same structural characteristics as those of the resin samples (III) prepared conventionally. The result also showed that UF resin samples (I and III) possessed 5 - 17 percent of free formaldehyde; the UF resin sample (II) had approximately zero formaldehyde percentage.
Authors and Affiliations
Mathew EDOGA
Keywords
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