Extraction of lignin using scCO2 and preparation of high-performance composite films with poly(vinyl alcohol)

Lignin (SCEL) was separated from steam-exploded eucalyptus wood fibers using a supercritical carbon dioxide (scCO2)–ethanol/water composite medium, which compared with traditional industrial alkaline extraction of lignin (AL) and high-temperature ethanol (EL). All three kinds were spray-dried to form microparticles. The obtained SCEL, AL, EL particles mixed poly(vinyl alcohol) (PVOH) prepare film. Compared the pure PVOH film, transmittance film ultraviolet light reduced more than 70% less 20%, tensile strengths SCEL/PVOH, AL/PVOH, EL/PVOH films increased by 79.2%, 39.1%, 66.0%, respectively. water contact angle 35.5° 95.3°, 59.5°, 66.7°, In terms performance improvement, SCEL had better effect. particle size small uniform, contained S-type structural units β-O-4 bonds, is conducive its uniform dispersion in matrix increases area between light, thereby improving anti-ultraviolet performance. hydrophilic groups large number hydrogen bonds PVOH, promotes combination at same time exposes hydrophobic lignin, improves mechanical properties hydrophobicity