LERMAB, IUT Hubert Curien, University of Lorraine, 7 rue Fusillés Résistance, 88000 Epinal, France
Xinyi Chen
LERMAB-ENSTIB, University of Lorraine, 27 rue Philippe Seguin, 88000 Epinal, France
Antonio Pizzi
LERMAB-ENSTIB, University of Lorraine, 27 rue Philippe Seguin, 88000 Epinal, France
Mathieu Petrissans
LERMAB, IUT Hubert Curien, University of Lorraine, 7 rue Fusillés Résistance, 88000 Epinal, France
Stephane Dumarcay
LERMAB, Faculté des Sciences, University of Lorraine, Blvd. des Aiguillettes, 54000 Nancy, France
Anelie Petrissans
LERMAB, IUT Hubert Curien, University of Lorraine, 7 rue Fusillés Résistance, 88000 Epinal, France
Xiaojian Zhou
Yunnan Key Laboratory of Wood Adhesives and Glue Products, College of Material Science and Engineering, Southwest Forestry University, Kunming 650224, China
Guanben Du
Yunnan Key Laboratory of Wood Adhesives and Glue Products, College of Material Science and Engineering, Southwest Forestry University, Kunming 650224, China
Baptiste Colin
LERMAB, IUT Hubert Curien, University of Lorraine, 7 rue Fusillés Résistance, 88000 Epinal, France
Xuedong Xi
Yunnan Key Laboratory of Wood Adhesives and Glue Products, College of Material Science and Engineering, Southwest Forestry University, Kunming 650224, China
Condensed tannin copolymerized with hyperbranched tris(2-aminoethyl)amine-urea formed by amine-amido deamination yields a particleboard thermosetting adhesive without any aldehydes satisfying the requirements of relevant standards for the particleboard internal bond strength. The tannin–triamine–urea cures well at 180 °C, a relatively low temperature for today’s particleboard hot pressing. As aldehydes were not used, the formaldehyde emission was found to be zero, not even in traces due to the heating of wood. The effect is ascribed to the presence of many reactive sites, such as amide, amino, and phenolic groups belonging to the three reagents used. The tannin appears to function as an additional cross-linking agent, almost a nucleating agent, for the triamine–urea hyperbranched oligomers. Chemical analysis by MALDI ToF and 13C NMR has shown that the predominant cross-linking reaction is that of the substitution of the tannin phenolic hydroxyls by the amino groups of the triamine. The reaction of tannin with the still-free amide groups of urea is rather rare, but it may occur with the rarer tannin flavonoid units in which the heterocyclic ring is opened. Due to the temperature gradient between the surfaces and the board core in the particleboard during hot pressing, the type and the relative balance of covalent and ionic bonds in the resin structure may differ in the surfaces and the board core.
