Self-crosslinking and film formation ability of liquefied black poplar

Black poplar wood, diethylene glycol (DEG), and sulphuric acid as a catalyst were used as starting reactants for liquefaction. Optimal conditions for liquefaction were established: reaction temperature 150 °C, reaction time 95 min, ratio of wood:DEG = 1:5 and 3% of sulphuric acid addition. The liquid mixture obtained by the liquefaction was composed of the real product of the reaction (the so called “excess solvent free liquefied wood” (ESFLW)) and of the remaining unreacted DEG. The unreacted DEG was successfully separated from the ESFLW and analysed with HPLC for levulinic acid content. Theoretical weight ratio between the wood and DEG required for the reaction was estimated. OH number investigation showed that the ESFLW in the liquid mixture contributes to maximally 60% of the free OH groups. The crosslinking of the ESFLW without any curing agents or additives was performed for the first time, and the drying stages investigated. FT-IR investigations demonstrated that the obtained crosslinked polymer film could be an ether and/or ester network.