Production and characterization of polyurethane foams from a simple mixture of castor oil, crude glycerol and untreated lignin as bio-based polyols

Polyurethane foams from bio-based polyols have been studied to produce sustainable and eco-friendly materials from biomass industrial wastes. Semi-rigid polyurethane foams were synthesized from physical mixtures of kraft lignin, castor oil and residual glycerol. The influence of different lignin contents (10, 12.5, 15, 17.5, 20, 25, 30 and 40%) on the foam properties was evaluated. An increase in the density and a decrease in the thermal stability were observed upon an increasing amount of lignin. The foam synthesized with 17.5% lignin showed better dimensional and thermal properties as well as the best cell homogeneity and this formulation was chosen for further investigation of the effects of the castor oil content, isocyanate/hydroxyl molar ratio (NCO/OH) and the blowing agent type. Increased foam densities and compressive strengths were observed with increased castor oil content in the foams. Similar results were observed upon increasing the NCO/OH molar ratio due to the higher amount of crosslinking reactions. The evaluation of the blowing agent effect showed that using cyclopentane and n-pentane, the foams showed higher densities and lower compressive strengths in comparison to the foams synthesized with the chemical blowing agent (water). This result can be explained by the faster volatilization of these organic blowing agents, producing smaller cells in comparison to the CO2 generated by the reaction of water with isocyanate. Green polyurethane foams with good properties and industrial interest were produced using a mixture of residual raw materials (glycerol and lignin) and castor oil as bio-based polyols. (C) 2016 Elsevier Ltd. All rights reserved.