@article{KleinRumpfKuschetal.2018,
  author    = {Stephanie Elisabeth Klein and Jessica Rumpf and Peter Kusch and Rolf Albach and Matthias Rehahn and Steffen Witzleben and Margit Schulze},
  title     = {Unmodified kraft lignin isolated at room temperature from aqueous solution for preparation of highly flexible transparent polyurethane coatings},
  series   = {RSC Advances},
  volume    = {8},
  number    = {71},
  publisher = {Royal Society of Chemistry (RSC)},
  issn      = {2046-2069},
  doi       = {10.1039/C8RA08579J},
  url       = {https://nbn-resolving.org/urn:nbn:de:hbz:1044-opus-43290},
  pages     = {40765 -- 40777},
  year      = {2018},
  abstract  = {Polyurethane (PU) coatings were successfully produced using unmodified kraft lignin (KL) as an environmentally benign component in contents of up to 80 wt\%. Lignin samples were precipitated from industrial black liquor in aqueous solution working at room temperature and different pH levels (pH 2 to pH 5). Lignins were characterized by UV-Vis, FTIR, pyrolysis-GC/MS, SEC and 31P-NMR. Results show a correlation between pH level, OH number and molecular weight Mw of isolated lignins. Lignin-based polyurethane coatings were prepared in an efficient one step synthesis dissolving lignin in THF and PEG425 in an ultrasonic bath followed by addition of 4,4-diphenylmethanediisocyanate (MDI) and triethylamine (TEA). Crosslinking was achieved under very mild conditions (1 hour at room temperature followed by 3 hours at 35 °C). The resulting coatings were characterized regarding their physical properties including ATR-IR, TGA, optical contact angle, light microscopy, REM-EDX and AFM data. Transparent homogeneous films of high flexibility resulted from lignins isolated at pH 4, possessing a temperature resistance up to 160 °C. Swelling tests revealed a resistance against water. Swelling in DMSO depends on index, pH of precipitation and catalyst utilization for PU preparation. According to AFM studies, surface roughness is between 10 and 28 nm.},
  language  = {en}
}