Comparison of UF synthesis by alkaline-acid and strongly acid processes

• Published in: Journal of applied polymer science 2012-02, Vol.123 (3), p.1764-1772
• Main Authors: Ferra, João M. M., Henriques, Ana, Mendes, Adélio M., Costa, Mário Rui N., Carvalho, Luisa H., Magalhães, Fernão D.
• Format: Article
• Language: English
• Subjects: alkaline-acid process; Applied sciences; Condensing; Exact sciences and technology; Flexibility; GPC/SEC; Materials science; Monitoring; Organic polymers; Physicochemistry of polymers; Polycondensation; Polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Resins; strongly acid process; Synthesis; urea-formaldehyde resins; Ureas
• ISSN: 0021-8995; 1097-4628; 1097-4628
• DOI: 10.1002/app.34642

This work discusses two processes for producing urea‐formaldehyde (UF) resins. One is the alkaline‐acid process, which has three steps: usually an alkaline methylolation followed by an acid condensation and finally the addition of a final amount of urea. The other process, the strongly acid process, consists of four steps, in which the first step involves a strongly acid condensation followed by an alkaline methylolation, a second condensation under a moderately acid pH and finally, methylolation and neutralization under a slight alkaline pH. Two resins were produced using the two above described processes. The molecular weight distribution (MWD) of the resins was monitored off‐line by GPC/SEC and the final resins were characterized by GPC/SEC and HPLC. These studies showed that the two resins differ greatly in chemical structure, composition, viscosity, and reactivity. The monitoring of MWD indicated that the first condensation under a strongly acid environment leads to the production of a polymer with a distinctly different chemical structure, therefore increasing the flexibility of polymer synthesis and opening the way to the improvement of end‐use properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012