Plywood Adhesives Using PF Resin with Fibrillated Bark Slurry from Radiata Pine (pinus Radiata D. Don): Utilization of Flavonoid Compounds from Bark and Wood. IV

AbstractIn 2003, the first adhesives into which considerable amounts of bark particles (< 63 μm) were incorporated were developed using radiata pine bark. The quality of bark containing adhesives has now been substantially improved by fibrillating the bark. The finely ground bark (< 63 µm) was fibrillated using a disk mill and formulated into plywood adhesives. The adhesives contained different ratios of fibrillated bark, phenol–formaldehyde (PF) resin and water. The gluability of the fibrillated bark adhesives was evaluated according to the Japanese Agricultural Standard (JAS) for Plywood and was found to be excellent with the proportion of PF resin to bark being 6 to 4 and 5 to 5 on a solid basis. The bark was fibrillated with water (in the ratio 1 to 10), freeze-dried and used for the adhesive formulations. The freeze-drying process is extremely expensive and was considered inappropriate for the production of wood adhesives. However, it was found that when the ground bark (< 1 mm) was fibrillated with a bark to water ratio of 1 to 3, the resulting bark slurry was able to be directly incorporated into a PF resin to produce high performance plywood adhesives. This improved process is more economic because it requires neither further fractionation of the ground bark nor freeze-drying of the fibrillated bark slurry. The fibrillated bark slurry adhesives are able to produce a high quality of bonding in plywood samples from not only radiata pine, but also hinoki and karamatsu veneers.