Resinification of NaOH-catalyzed phenolated wood–phenol mixture with formalin for making molding materials

NaOH-catalyzed phenolated wood-phenol-formalin co-condensed novolak type resin was prepared in two stages. Birch wood meal was first phenolated by using NaOH as a catalyst at an elevated temperature (i.e. 250 °C), and then formalin solution together with oxalic acid was added to the phenolated wood-phenol mixture obtained. The relationships among reaction parameters and phenolation/ resinification yields, flow properties of the resinified phenolated wood, and the physico-mechanical properties of the resinified phenolated wood-based molding materials were studied. The yields obtained due to resinification of the phenolated wood were found to depend, greatly, on the phenol-formalin molar ratio. Moreover, the melt flow properties (i.e. flow properties and viscosity) of the resinified NaOH-catalyzed phenolated wood reached or slightly exceeded those of commercial novolak resin and was greatly improved in comparison to the NaOH-catalyzed phenolated wood-based molding materials alone. Furthermore, the flexural properties of the resinified phenolated wood-based molding materials were determined to be much similar to or better than those of commercial novolak resin-based molding materials and much greater than those of NaOH-catalyzed phenolated woodbased molding materials alone. On the other hand, the resinified phenolated wood-based molding materials were more hydrophobic and biodegradable than those of commercial novolak resin-based molding materials and less hydrophobic and biodegradable than NaOH-catalyzed phenolated woodbased molding materials alone.