Resinification of Alkali-Catalyzed Liquefied Phenolated Wood and its Characterization as the Novolak-Type Phenolic Resins

Abstract

The reaction of wood meal with phenol resulted large amounts of non-reacted phenol, which further allowed reaction with formaldehyde. The effects of various reaction parameters for the preparation of wood-based phenolic resins on their properties have been discussed. The optimum conditions (i.e., 80% consumption of phenol) of wood-based phenolic resin preparation were found to be a formaldehyde:phenol mole ratio of 1.6:1, a pH of 2.51, a temperature of 130°C, and time 1 h. Both melt-flow behavior and molecular weight of the wood-based phenolic resins changed with the change in reaction parameters. For most cases, the melt-flow properties of the wood-based phenolic resins were close to those of commercial novolak resins. The flexural mechanical properties of wood flour-filled molded materials of wood-based phenolic resins, which were prepared at the formaldehyde:phenol mole ratios of 0.85:1 and 1.16:1, were comparable to those of commercial novolak resins. Moreover, molded wood-based phenolic resins, prepared at same mole ratios of formaldehyde:phenol, showed better resistance to immersion in water and burial in active composting soil in comparison with those prepared under other conditions. Generally, wood-based phenolic resins with higher reacted phenol had properties close to those of commercial novolak types.