Extrusion of Solid Wood Impregnated with Phenol Formaldehyde (PF) Resin: Effect of Resin Content and Moisture Content on Extrudability and Mechanical Properties of Extrudate
A new deformation technique of wood flow forming is promising for industrial uses of solid wood. Flow deformability, size stability, and good mechanical properties were obtained by using wood impregnated with low molecular weight phenol formaldehyde (PF) resin. In this study, to clarify the effect of the PF resin and moisture contents in wood on the flow deformability (extrudability) and the mechanical properties of the product (extrudate), a lateral extrusion was conducted by using wood impregnated with various contents of PF resin and three levels of moisture content. The results indicated that the extrudability of wood impregnated with PF resin improved with an increase in both PF resin and moisture content. The mechanical properties of the extrudate worsened with increases in the moisture content of the wood impregnated with PF resin. Because most of the water in the wood remained in the mold during the extrusion process, chemical changes of the wood substance and PF resin occurred due to steam forming under the high temperature and pressure of the extrusion. The steam worsened the mechanical properties of the extrudate.
Integrated analysis of solid-state NMR spectra and nuclear magnetic relaxation times for the phenol formaldehyde (PF) resin impregnation process into soft wood
The effects of phenol formaldehyde (PF) resin impregnation into Japanese cedar plates were studied by the integrated analysis of solid-state NMR spectra and relaxation times. 13C cross-polarization/magic angle spinning (CP-MAS) NMR spectra showed that PF resin permeated near carbohydrate polymers as well as lignin regions, providing hydrophobicity in a woody material. Additionally, 13C pulse saturation transfer/magic angle spinning (PST-MAS) NMR spectra revealed that the molecular mobility of cellulose endocyclic groups was suppressed by the PF resin impregnation. Spin-lattice relaxation times in the laboratory frame, T1H and T1C, for both untreated and impregnated woods decreased in humid conditions while they were increased by the PF resin impregnation. Meanwhile, spin-lattice relaxation in the rotation frame, T1ρH, decreased in humid conditions as well as being a result of the PF resin impregnation. According to the tendencies of the T1H, T1C, and T1ρH values associated with the PF resin impregnation, although faster molecular motions of lignin OCH3 group were increased in the MHz frequency range, slower molecular motions of the cellulose ring were suppressed in the kHz frequency range, which confirmed the result from the 13C PST-MAS NMR spectra.
Acetyl Distribution in Acetylated Whole Wood and Reactivity of Isolated Wood Cell-Wall Components to Acetic Anhydride
Lignin, holocellulose, cellulose, and hemicelluloses were isolated from pine wood and reacted with acetic anhydride. The order of reactivity was found to be lignin < hemicelluloses << holocellulose. Cellulose did not react. At a level of bonded acetyl where all the hydroxyl groups were substituted on the lignin polymer, only about 20% of the total theoretical hydroxyl groups on the holocellulose were substituted. The data suggest that in the reaction of chloroacetic anhydride with whole wood, the initial rate-controlling step is the rate of diffusion of reactive chemical into the cell wall.