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Integrated analysis of solid-state NMR spectra and nuclear magnetic relaxation times for the phenol formaldehyde (PF) resin impregnation process into soft wood
- Nishida, Masakazu, Tanaka, Tomoko, Miki, Tsunehisa, Hayakawa, Yoshio, Kanayama, Kozo
- RSC advances 2017 v.7 no.86 pp. 54532-54541
- Cryptomeria japonica, carbon, cellulose, formaldehyde, hydrophobicity, magnetism, nuclear magnetic resonance spectroscopy, phenol, softwood, stable isotopes
- 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.