Preparation and characterization of bio-polyol and bio-based flexible polyurethane foams from fast pyrolysis of wheat straw

Abstract Crude bio-oil from fast pyrolysis of wheat straw was extracted with ethyl acetate, and the extracted bio-oil was used as bio-polyol (hydroxyl number: 77.8 mg KOH/g) for the preparation of bio-based flexible polyurethane foams. GC–MS and FTIR analysis of the extracted bio-oil or bio-polyol evidenced that it has the presence of a larger amount of compounds containing multiple hydroxyl groups than the crude bio-oil. The foams were characterized for their physical, mechanical and thermal properties. Response surface methodology(RSM) was employed to optimize several independent variables (30–50 wt.% of bio-polyol, 10–30 wt.% of polymethylene polyphenylene isocyanate (PM200), 10–30 wt.% of polymeric diphenylmethane diisocyanate (PMDI), and 0.5–1.5 wt.% of cross linking agent, total amounts of isocyanates (PM200 and PMDI) was kept at 40 wt.%, all based on weight of total polyol) for their effects on the foam resilience. Under the optimized conditions, i.e., 30 wt.% bio-polyol, 17.9 wt.% PM200 and 22.1 wt.% PMDI, 0.5 wt.% cross linking agent, the resulted foam has resilience of 37.0% and is thermally stable up to 200 °C.