Study On Bonding Technology Of Cryptomeria Fortunei Hooibenk And The Characterization Of Glue-Wood Interface

Small-diameter plantation wood can be used to manufacture high-quality products (e.g. glued-laminated timber, finger-jointted timber and LVL) by gluing. It could not only improve the value addition of products, but also ease the contradiction between supply and demand of wood. But the phenomenon of warp and even crack often appears on glued products, which would be related to the glue-wood interface. Basing on the research progresses and advanced research methods at home and abroad in this field, study on both macro bonding properties and characterization of the glue-wood interface were carried out in this study, to enrich the studies on bonding mechanism of the glue-wood interface, and to provide technical supports for utilization of plantation wood in depth.In this paper, plantation wood of Cryptomeria fortunei Hooibenk was selected as study material with EPI and UF as adhesives. The macro bonding properties, micro penetration properties, and micro mechanical properties of the glue-wood interface were investigated, and main results were as follows.1) Except for one or two cases, the bonding properties of EPI and UF met the standard of JAS SE-8. For EPI, the optimum gluing condition was:press pressure1.0MPa, press time30min, and spread rate180g/m2, with T-T gluing combination. For UF, the optimum gluing condition was:press pressure0.7MPa, press time31min, and spread rate180g/m2, with T-T gluing combination. Under optimum gluing condition, both the shear strength and the water delamination degree of UF were better than those of EPI.2)According to photographs of fluorescence microscope, the penetrability of UF was better than that of EPI, while the penetrability of early wood was better than that of late wood. Besides, the penetrability on the tangential section was similar to that on the radial section for EPI, but the former was better than the later for UF.3)The results from fluorescence microscope, confocal laser scanning microscope, and nanoindentation confirmed that UF penetrated into cell walls and the mechanical properties of cell walls increased obviously, while EPI failed. Although the penetration of UF in the cell walls was not detected by modulus mapping, the distribution of mechanical properties on each layer of cell walls can be characterized quantitatively.4)The results of nanoindentation test showed that elastic modulus and hardness of UF were higher than those of EPI. On the wood/UF interphase, elastic modulus in wood interphase region increased firstly and then decreased to a steady value as the test point going away from glue line, and hardness showed a similar variation tendency. The schematic illustration on variation of mechanical properties in the glue-wood interface could be used to predict the fracture position and evaluate the quality of the glue line.