Lignins as macromonomers for polyurethane synthesis: A comparative study on hydroxyl group determination

Abstract

The hydroxyl group contents of four technical lignins [Indulin AT (Meadwestvaco), Alcell (Repap), Curan 27‐11P (Borregaard LignoTech), and Sarkanda (Granit SA)] were investigated in view of their valorization as polyols in polyurethane synthesis. The different hydroxyl group contents were determined by the following methods: titration and 1H‐NMR, 13C‐NMR, and 31P‐NMR spectroscopy. The titration method chosen was on the basis of a standard method commonly used to characterize commercial polyols for polyurethanes synthesis. The values of the total and phenolic hydroxyl contents determined by the different techniques were found to be in good agreement. For the total hydroxyl contents, coefficients of variation of 5.6% (Alcell), 3.2% (Indulin AT), 2.3% (Sarkanda), and 6.2% (Curan 27‐11P) were established. For the phenolic hydroxyl contents, a good correlation was observed between data obtained from 31P‐NMR and 13C‐NMR for all lignin samples, except for the Sarkanda lignin, for which a relatively high coefficient of variation (12.6%) was found. For softwood lignins (Indulin AT and Curan 27‐11P), the phenolic hydroxyl content determined by 1H‐NMR was always lower than that deduced from 31P‐NMR and 13C‐NMR spectroscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Determination of Phenolic Hydroxyl Groups in Technical Lignins by Ionization Difference Ultraviolet Spectrophotometry (∆ε-IDUS method)

“…Assigned peaks corresponds well with previously reported regions [30]. For milox lignin, phenolic OAc comprises the peak number 6, secondary OAc the peaks number 5 and 4, and primary OAc the peaks number 1, 2 and 3.…”

New Ionic Liquid for the Dissolution of Lignin

“…The content of hydroxyl groups was obtained by integration of the following spectral regions: aliphatic hydroxyls (149.4-145.5 ppm), syringyl (S) phenolic hydroxyls (143.3-141.9 ppm), condensed phenolic units (difference between 144.3-141.3 ppm and 143.3-141.9 ppm as previously done by Cateto et al (2008) Spectroscopy FT-IR FTIR spectra were obtained with a Perkin Elmer instrument, System 2000, using pellets of lignin mixed with KBr (lignin content of 1%). Spectra were recorded between 400 and 4000 cm -1 with a resolution of 2 cm -1 .…”

Microwave-assisted extraction of lignin from triticale straw: Optimization and microwave effects

“…All chemical shifts are reported relative to the signal of the product of water with the phosphitylating reagent (132.2 ppm). The content of hydroxyl groups was obtained by integration of the following spectral regions: aliphatic hydroxyls (149.1-144.6 ppm), syringyl (S) phenolic hydroxyls (143.3-141.9 ppm), condensed phenolic units (difference between 144.3-141.3 ppm and 143.3-141.9 ppm as previously done by Cateto et al (2008)), guaiacyl (G) phenolic hydroxyls (140.6-138.6 ppm), p-hydroxyphenyl (H) phenolic hydroxyls (138.4-137.2 ppm), carboxylic acids (135.3-134.4 ppm).…”