title: Cellulose nanofibrils as filler for adhesives: effect on specific fracture energy of solid wood-adhesive bonds.
abstract: Cellulose nanofibrils were prepared by mechanical fibrillation of never-dried beech pulp and bacterial cellulose. To facilitate the separation of individual fibrils, one part of the wood pulp was surface-carboxylated by a catalytic oxidation using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as a catalyst. After fibrillation by a high pressure homogenizer, the obtained aqueous fibril dispersions were directly mixed with different urea-formaldehyde-(UF)-adhesives. To investigate the effect of added cellulose filler on the fracture mechanical properties of wood adhesive bonds, double cantilever beam specimens were prepared from spruce wood. While the highest fracture energy values were observed for UF-bonds filled with untreated nanofibrils prepared from wood pulp, bonds filled with TEMPO-oxidized fibrils showed less satisfying performance. It is proposed that UF-adhesive bonds can be significantly toughened by the addition of only small amounts of cellulose nanofibrils. Thereby, the optimum filler content is largely depending on the adhesive and type of cellulose filler used.
authors.affiliation: Department of Material Sciences and Process Engineering, Institute of Wood Science and Technology, BOKU-University of Natural Resources and Life Sciences, Konrad Lorenz Straße 24, 3430 Tulln a.d. Donau, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Veigel
authors.affiliation: Wood K plus-Competence Centre for Wood Composites and Wood Chemistry, St.-Peter-Straße 25, 4021 Linz, Austria.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Müller
authors.affiliation: Erich Schmid Institute of Materials Science, Austrian Academy of Sciences and Institute of Metal Physics, University of Leoben, Jahnstraße 12, 8700 Leoben, Austria.
authors.forename: Jozef
authors.initials: J
authors.lastname: Keckes
authors.affiliation: Department of Material Sciences and Process Engineering, Institute of Wood Science and Technology, BOKU-University of Natural Resources and Life Sciences, Konrad Lorenz Straße 24, 3430 Tulln a.d. Donau, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Obersriebnig
authors.affiliation: Department of Material Sciences and Process Engineering, Institute of Wood Science and Technology, BOKU-University of Natural Resources and Life Sciences, Konrad Lorenz Straße 24, 3430 Tulln a.d. Donau, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gindl-Altmutter
keywords: Adhesive; Cellulose; Filler; Fracture energy; Nanofibrils