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. 2013 Jan 28;6:12. doi: 10.1186/1754-6834-6-12

Figure 4.

Figure 4

Effect of lignin addition on the compressive strength 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.