Ethylated Urea - Ether - Modified Urea - Formaldehyde Resins, Part I: Structural and Physicochemical Properties
Journal Title: Leonardo Electronic Journal of Practices and Technologies - Year 2006, Vol 5, Issue 9
Abstract
First, phenol - formaldehyde (PF) and urea - formaldehyde (UFII) resins were separately conventionally prepared in our laboratory. Also, UF resin synthesized from the acid modified synthesis procedure was synthesized in a purely acid medium of pH 1.0, FU molar ratio of 1.0 and at 50oC (one-stage acid modified-synthesis procedure). Subsequently, the UF resin II was modified during synthesis by incorporating ethylated urea-ether (EUER) (i.e. UFIII) and glycerol (GLYC) (i.e. UFV) cured with and without acid curing agent. The structural and physicochemical analyses of the various resin samples were carried out. The results showed that the unmodified UF resin (UF II) synthesized in acid medium of pH 1.0, F/U molar ratio 1.0, and at 50oC, cured in absence of acid curing catalyst, 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 cured UF resin. Modification of the UF resin(UF II) with ethylated urea-ether and glycerol to produce UF resins III and respectively V prominently increased the absorbance of methylene and ether groups in the spectra which are consistent with increased hydrophobicity and improved hydrolytic stability. For the conventional UF resin (UF I), the only clear distinction between spectra for the UF resin II and UF resins (III/V) is the presence of diminished peaks for methylene groups at 2.2 ppm. The relationship between the logarithmic viscosity of cured PF resin with time showed continuos dependence of viscosity with time during cure up to 70 minutes. Similar trends were shown by UF resins (III/V), cured in absence of acid catalyst. In contrast, the conventional UF resins I and UF IV (i.e. UF II cured with NH4CL) showed abrupt discontinuity in viscosity with time just after about 20 minutes of cure.
Authors and Affiliations
Mathew EDOGA
Keywords
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