Effects of the drying process on the shear strength and morphology of the bonding interface of laminated wood

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ORIGINAL ARTICLE

Effects of the drying process on the shear strength and morphology of the bonding interface of laminated wood Mingjie Guan1   · Keke Du1 · Xinyuan Tang1 Received: 6 January 2020 / Accepted: 2 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract To investigate the influence of the drying process on the bonding properties of laminated wood, a poplar veneer was impregnated with low molecular-weight phenol formaldehyde (PF) resin and laminated wood was created and studied. The effects of drying temperature, drying time and solid content of the PF resin on the moisture content (MC) of the impregnated veneer after drying and the shear strength of the laminated wood were analyzed with an orthogonal experiment. The microscopic mechanism of the bonding performance of the laminated woods was investigated by fluorescence microscopy. The experimental results showed that the higher the PF resin solid content was, the larger the weight gain percentage of the impregnated veneer was. In addition to drying temperature and drying time, the solid content of PF also had a significant influence on the MC of the impregnated veneer after drying. The shear strength of the laminated wood affected by the drying temperature, solid content of PF and drying time and the drying temperature had a more significant effect than the other two factors. The best drying process was a drying temperature of 50 °C, a drying time of 2 h, and a PF solid content of 30%. The fluorescence analysis showed that the shear strength of the laminated wood was affected by the intensity of the PF resin on the bonding interface, and the average and effective penetration depth of the PF resin in the veneer increased with the increase in the drying temperature.

1 Introduction Laminated wood is a popular engineered wood product in the wood industry. Gaborik et al. (2016) reported that the laminated wood is usually comprised of multiple layers of wood, which are most frequently in the form of impregnated veneers that have been dried and pressed together. It can be widely used for floor beams, decks, girders and other construction building materials (Kasal and Heiduschke 2004; Kim and Kim 2006). Most of the resin used in veneer impregnation is phenol–formaldehyde (PF) and research shows that the PF-impregnated layers impart superior mechanical strength and fire resistance to the laminated wood (Thebault et al. 2017). The bonding strength of laminated wood is a critical property for ensuring the final product quality. The bonding performance of impregnated veneers is affected by a variety of complex factors, such as the veneer quality, adhesive types, impregnating * Mingjie Guan [email protected] 1



College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, China

parameters, drying conditions, and hot press parameters (Aydin and Colakoglu 2005; Gindl et al. 2005; Knorz et al. 2016; Mahlberg et al. 2001; Sernek et al. 2008; Tenorio et al. 2011). The drying of an impregnated veneer is one