Preparation of bio-polyols by liquefaction of hardwood residue and their application in the modification of polyurethane foams

Hardwood residue (HR), a byproduct of paper industry, was liquefied by using polyethylene glycol 400 (PEG400) and ethylene carbonate (EC) as the liquefaction solvents, and concentrated sulfuric acid as the catalyst to produce bio-polyols (HRLP), which were used to synthesize polyurethane (PU) foams. The effects of conditions on the properties of HRLP and modified PU foams were investigated and the mechanism of biomass liquefaction was discussed. The optimum conditions of liquefaction were obtained as follows: reaction temperature of 160 °C, reaction time of 60 min, ratio of PEG400/EC of 8:2 (w/w), and ratio of liquid/solid of 5:1 (w/w). The characterization of HRLP modified PU foams suggested that HRLP could partially replace the petroleum polyols to synthesize PU foams. With the increase of the replacement percentage of HRLP, the apparent density and compressive strength of the foams increased firstly, and then decreased. Meanwhile, the thermal stability was improved slightly.