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13 C NMR investigation of the reaction in water of UF resins with blocked emulsifiable isocyanates
Author(s) -
Despres A.,
Pizzi A.,
Delmotte L.
Publication year - 2005
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.22498
Subject(s) - isocyanate , urea formaldehyde , urea , polymer chemistry , methylene , chemistry , amide , hydroxymethyl , formaldehyde , carbon 13 nmr , polyurethane , proton nmr , organic chemistry , nuclear chemistry , adhesive , layer (electronics)
A solid state 13 C NMR study of hardened networks obtained by the reaction of blocked and nonblocked isocyanates (pMDI) with urea‐formaldehyde (UF) resins in water showed different results according to the temperature of the reaction. At high temperature, in water, both a nonblocked or an emulsifiable, blocked isocyanate, appear to crosslink with UF resins through the formation both of traditional methylene bridges connecting urea to urea and of urethane bridges. The latter have been confirmed by 13 C NMR to form in water by reaction of the isocyanate NCO group with the hydroxymethyl groups of the UF resin. At ambient temperature, UF/pMDI resins where the pMDI is a emulsifiable blocked isocyanate, do not appear to form urethanes to any great extent but rather to crosslink through the usual UF resin urea to urea methylene bridges. Even in this case, when urethane bridges appear to be absent, evidence of crosslinking in water through reaction of the isocyanate with the NH 2 and NH amide of the UF resin has not been observed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 589–596, 2006