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Unmodified kraft lignin isolated at room temperature from aqueous solution for preparation of highly flexible transparent polyurethane coatings

  • 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.

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Document Type:Article
Author:Stephanie Elisabeth Klein, Jessica Rumpf, Peter Kusch, Rolf Albach, Matthias Rehahn, Steffen Witzleben, Margit Schulze
Parent Title (English):RSC Advances
First Page:40765
Last Page:40777
Publisher:Royal Society of Chemistry
Publishing Institution:Hochschule Bonn-Rhein-Sieg
Date of first publication:2018/12/10
Copyright:This journal is © The Royal Society of Chemistry 2018. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.
Funding:This research was supported by the Federal Ministry of Education and Research (BMBF) program "IngenieurNachwuchs" project LignoBau (03FH013IX4).
Departments, institutes and facilities:Fachbereich Angewandte Naturwissenschaften
Institut für Technik, Ressourcenschonung und Energieeffizienz (TREE)
Projects:LignoBau - IngenieurNachwuchs 2014: Lignin-basierte Polymere für bauchemische Anwendungen (DE/BMBF/03FH013IX4,13FH013IX4)
Dewey Decimal Classification (DDC):5 Naturwissenschaften und Mathematik / 54 Chemie / 540 Chemie und zugeordnete Wissenschaften
Entry in this database:2019/01/08
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 3.0