Vibrational spectroscopic studies on wood and wood-based materials (V) infrared microspectroscopic investigation for penetration behavior of isocyanate adhesives at wood-dowel joints

摘要

Wood dowel (Acer mono) was joined into wood member (Cryptomeria japonica) by a polymeric MDI (PMDI) or a polyurethane resin, which is an isocyanate adhesive. Infrared microspectrosopic spectra at the joints were 2- dimensionally measured by diffuse reflectance method, and then NCO group was identified due to its asymmetric stretching vibrational band (2270cm{sup}(-1)). The distributions of the adhesives (isocyanate compounds) around the joints were displayed by colors corresponding to the band intensity at 2270cm{sup}(-1). The color maps exhibited that the PMDI excessively penetrates into the wood member in the axial direction because of its low viscosity (ca. 0.2 Pa·s), and indicated that only the fluid components in the polyurethane resin (ca. 200 Pa·s), which are not so large, move from the glue line to the wood member.