Figure 5From: Effect of replacing polyol by organosolv and kraft lignin on the property and structure of rigid polyurethane foamEffect of lignin addition on the density of rigid polyurethane foams. Ratio of lignin to polyol, molar ratio of the hydroxyl groups from lignin to those from polyol (Voranol 270); HEL, hardwood ethanol organosolv lignin; HKL, hardwood kraft lignin.Back to article page