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Polymers 2016, 8(3), 57;

Acid Ionic Liquids as a New Hardener in Urea-Glyoxal Adhesive Resins

Department of Wood and Paper Sciences and Technology, Faculty of Natural Resources, Semnan University, Semnan 35131-19111, Iran
LERMAB-ENSTIB, University of Lorraine, Epinal 88000, France
Author to whom correspondence should be addressed.
Academic Editor: Frank Wiesbrock
Received: 23 January 2016 / Revised: 8 February 2016 / Accepted: 17 February 2016 / Published: 24 February 2016
(This article belongs to the Special Issue Renewable Polymeric Adhesives)
Full-Text   |   PDF [8641 KB, uploaded 24 February 2016]   |  


The effect of acidic ionic liquid (IL) as a new catalyst on the properties of wood-based panels bonded with urea-glyoxal (UG) resins was investigated. Different levels of N-methyl-2-pyrrolidone hydrogen sulfate ([HNMP] HSO4 (0, 1, 2, 3 wt %)) were added to prepared UG resin. The resin was then used for preparing laboratory particleboard panels. Then, the properties of the prepared panels were evaluated. The structure of the prepared UG resin was studied by 13C NMR, and thermal curing behavior of the resin before and after the addition of IL was measured by DSC. Additionally, the main oligomers formed in the UG reaction were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectroscopy. The results indicated that IL can be used as an efficient catalyst for UG resin. The physicochemical tests indicated that the addition of [HNMP] HSO4 from 0 to 3 wt % decreased the pH value of the glue-mix, and the pH decreased on curing to the same level as urea-formaldehyde resins. The gel accelerated with increasing catalyst content and with the decreasing of the pH in the UG resin. The panels prepared with IL had higher mechanical strength and dimensional stability compared to those made from UG resins containing NH4Cl. Scanning electron microscope (SEM) micrographs showed that the panels prepared with ionic liquid presented low porous. DSC analysis showed that the addition of IL to the UG resin decrease the energy of activation of the curing reaction to render possible cross-linking. The MALDI TOF results indicated a preponderant linearity of the oligomers formed, implying a high energy of activation of curing for UG resins. View Full-Text
Keywords: acidic ionic liquid; urea-glyoxal resin; catalyst; MALDI TOF; 13C NMR; DSC acidic ionic liquid; urea-glyoxal resin; catalyst; MALDI TOF; 13C NMR; DSC

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Younesi-Kordkheili, H.; Pizzi, A. Acid Ionic Liquids as a New Hardener in Urea-Glyoxal Adhesive Resins. Polymers 2016, 8, 57.

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