Influence of glyoxal on curing of urea-formaldehyde resins |
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| Affiliation: | 1. Laboratory of Organic Synthesis, Tomsk State University, Tomsk 634050, Russia;2. Energetic Systems, Fraunhofer Institute for Chemical Technology ICT, Pfinztal, 76327, Germany;1. Department of Dentistry, Federal University of Parana, Curitiba, Parana, Brazil;2. Postgraduate Program in Dentistry, Department of Dentistry, State University of Ponta Grossa, Parana, Brazil;3. Department of Pharmaceutical Sciences, State University of Ponta Grossa, Parana, Brazil;4. Department of Pharmacy, Federal University of Parana, Curitiba, Parana, Brazil;5. Department of Chemistry, State University of Ponta Grossa, Parana, Brazil;6. Department of Materials Engineering, State University of Ponta Grossa, Parana, Brazil;1. DEMad, Instituto Politécnico de Viseu, 3504-510, Viseu, Portugal;2. LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal;3. ARCP-Associação Rede de Competência Em Polímeros, 4200-355, Porto, Portugal;4. Euroresinas – Indústrias Químicas, 7520-195, Sines, Portugal;1. EuroResinas – Indústrias Químicas, 7520-195, Sines, Portugal;2. ARCP - Associação Rede de Competência Em Polímeros, Rua Dr. Júlio de Matos 828/882, Porto, Portugal;3. DEMad - Instituto Politécnico de Viseu, Campus Politécnico de Repeses, 3504-510, Viseu, Portugal;4. LEPABE-Faculdade de Engenharia da Universidade Do Porto, Rua Dr. Roberto Frias S/n, 4200-465, Porto, Portugal;1. Department of Organic Chemistry, University of Guilan, University Campus 2, Rasht, Iran;2. Department of Organic Chemistry, Faculty of Sciences, University of Guilan, Rasht, Iran;3. LERMAB-ENSTIB, University of Lorraine, Epinal, France;4. Esfahan University of Technology, Iran |
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| Abstract: | In the present paper, the effect of glyoxal on the gel formation within the adhesive systems based on urea-formaldehyde (UF) resins is shown. A reduction of formaldehyde content in wood-based panels by decreasing the formaldehyde/urea molar ratio in the UF resins leads to increasing of the UF resin gel time, and impairing the qualitative characteristics of the UF-based wood materials. Glyoxal is shown to speed up the crosslinking of the macromolecules as well as significant reduction of gel time of adhesive composition. The first reason is the result of reaction between glyoxal and ammonium ion leading to protons releasing. Another reason is that glyoxal and its interaction products react with macromolecules of the UF resin forming a three-dimension cross-linked structure. The gel time and the pot life of the UF resin are measured by the oscillatory viscometer. Formation of the UF cross-linked resin structure with glyoxal and a curing catalyst (ammonium sulfate) is studied using dispersion Raman scattering spectroscopy. Particleboards (PB) are produced using different amount of glyoxal and formaldehyde/urea molar ratio in the UF resin. The properties are evaluated according to the European Standards and include density, internal bond, thickness swelling moisture content and formaldehyde content. |
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| Keywords: | Adhesives for wood Cure Crosslinking Resin-based composites Raman spectroscopy |
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