Antioxidant activity of unmodified kraft and organosolv lignins to be used as sustainable components for polyurethane coatings

• Published in: JCT research Vol. 16; no. 6; pp. 1543 - 1552
• Main Authors: Klein, Stephanie E., Rumpf, Jessica, Alzagameem, Abla, Rehahn, Matthias, Schulze, Margit
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.11.2019; Springer Nature B.V
• Subjects: Antioxidants; Chemistry and Materials Science; Coatings; Corrosion and Coatings; Industrial Chemistry/Chemical Engineering; Lignin; Materials Science; Polymer Sciences; Polyurethane resins; Pulping; Scavenging; Sodium carbonate; Spin coating; Surfaces and Interfaces; Thin Films; Tribology; Lignocellulose feedstock; Antioxidant activity; Organosolv lignin; Total phenol content; Folin–Ciocalteu assay; Biomass; Kraft lignin
• ISSN: 1547-0091; 1935-3804; 2168-8028
• DOI: 10.1007/s11998-019-00201-w

The antioxidative capacity of four different kraft lignins (KL) and one additional organosolv lignin (OSL) was studied using the Folin–Ciocalteu (FC) assay. To do so, the corresponding FC assay procedure was adapted and optimized to be appropriate for lignin analysis. Different solvents were tested, and DMSO and saturated sodium carbonate (Na 2 CO 3 ) for pH adjustment showed the best results. The absorption wavelength of 740 nm was chosen due to highest determination coefficients. Continuous calibration is recommended on a daily basis to guarantee accuracy. The antioxidant capacity and related radical scavenging activity of various lignins were correlated with the biomass nature (soft wood vs grasses) and pulping methods (kraft vs organosolv). The results show higher antioxidant activity for kraft vs organosolv lignins. First lignin-derived polyurethane coatings were prepared using the unmodified kraft lignin. The films, prepared via spin coating, show a high flexibility and transparency.