Studies on the preparation and the characterization of resinified wood foams

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Resinified wood foams were first tried to be prepared from chemically modified wood. The authors have found that esterified and etherified wood can be dissolved in polyfunctional organic compounds. As one of the application of the solution, the resinified wood foam, being a composite material from air and wood resins, has been investigated. The foam could be obtained as a resinified-wood-polyurethane foam by combined uses of a chemical reaction method and an open-mold-one-shot method. That is, after dissolving chemically modified wood such as allylated wood powders into polyhydric alcohols as 1,4-butanediol or bisphenol A with a concentration more than 50%, varying amounts of water and polyisocyanate compounds are added as a foaming agent and a hardener, respectively. When the mixed solution is allowed to stand at about 100゜C, foaming and resinification of the solution starts within 2 min. The products are wood-based polyurethane foams. The density of the foam takes values in the range … More of about 0.04 to 0.6 g/ <cm^3> , depending on blending composition of the raw materials. Even with the foam having the density of 0.04 g/ <cm^3> , a substantial strength and a restoring force for compression deformation can be furnished.In the advanced stage of this study, more prominent foams could be found to be obtainable from untreated-wood solutions. Wood chips and meals have found to be dissolved in polyhydric alcohols, polyethylene glycohol (PEG), bisphenols and so forth. Especially, the preparation of foams from the PEG solution has been systematically studied. The wood components and PEG in the solutions have first been reacted with propylene oxide or <epsilon> -caprolactone, introducing various lengths of side chains with a hydroxyl end group. Then, by adding foaming agents such as water and, freon, adjusting agents for foaming and polyisocyanate compounds, followed by heating, resinified wood foams with wide ranges of density could be obtained. The qualities of these foams are comparable to those of the corresponding commercial products. Less