Wood liquefaction and its application to Novolac resin
Wood liquefaction was conducted using phenol as a reagent solvent with a weak acid catalyst in two different reactors: (Alma et al., 1995a.) an atmospheric glass reactor and (Alma et al., 1995b.) a sealed Parr® reactor. Residues were characterized by wet chemical analyses, Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The FT-IR spectra of the liquefied wood residues showed a peak at 1735 cm-1, which was attributed to the ester carbonyl group in xylan, disappeared in the spectrum of the residue from liquefied wood under a sealed reaction system, indicating different liquefaction mechanisms of the liquefaction reactions conducted in the atmospheric glass reactor versus sealed metal reactor. The crystallinity index of the liquefied wood residues was higher than that of the original wood particles. Two different liquefied wood/phenol/formaldehyde (LWPF) resins were synthesized from liquefied wood reacted in an atmospheric glass reactor (LWPF-A) and a sealed metal reactor (LWPF-B). The onset cure temperature of LWPF-A resin was higher than LWPF-B while the peak temperatures of these two resins were close. The activation energies of two LWPF resins were similar to each other and to a lignin-phenol-formaldehyde resin. However, they both were higher than a typical phenolformaldehyde resin. The compression molded panels made with LWPF-A resin performed better physical and mechanical properties than that made with LWPF-B resin.