Rigid polyurethane foams from unrefined crude glycerol and technical lignins

The need for green materials has driven interest in the preparation of rigid polyurethane foam (PUF) from various biomass types. The present study aims at increasing bio-based content by utilizing by-products from both the pulp and paper and biodiesel industries. Bio-based polyols from respective liquefaction of kraft lignin, organosolv lignin and lignosulphonate in crude glycerol were employed to prepare rigid PUFs. The highest foam compressive strength was 345 kPa with density 79 kg m−3; thermal conductivity was 0.039 W m−1 K−1 and the corresponding material had 44 wt% renewable content. Thermal characteristics and biodegradability were also evaluated. Technical lignin type was found to determine product properties to a large extent. Based on the use of existing industrial scale by-products in this study, the findings can be beneficial for present and future biorefineries in the valorization of lower value by-product streams.