Preparation of Two-Component Polyurethane Coatings from Bleached Liquefied Wood

Abstract

Liquefied wood-based polyurethane wood coatings of an aesthetically acceptable light colour were prepared and characterised. Liquefied black poplar wood was obtained by solvolysis in a polyethylene glycol/glycerol mixture, and it was bleached with hydrogen peroxide. The bleaching treatment converted liquefied wood from a dark brown to a yellowish product. Polyurethane films were prepared by the curing of liquefied wood with polymeric diphenylmethane diisocyanate or trimethylolpropane toluene diisocyanate prepolymer (TMP/TDI) isocyanate-type hardeners. It was found that the selected properties of the films prepared from the bleached liquefied wood were, in general, equivalent to those prepared from unbleached liquefied wood. The mechanical properties of the films obtained with the TMP/TDI curing agent were acceptable for wood coating applications. The initial poor resistance of the films to water and ethanol was substantially improved by the addition of n-octyltriethoxysilane to the liquefied wood prior to the preparation of the polyurethane coatings; the hardness of the films also increased.