Characterization of Fractions Obtained from Two Industrial
Softwood Kraft Lignins
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Abstract
With increasing interest in using
lignin as an alternative material
to petroleum-based chemicals (e.g., in the manufacture of carbon fibers
or adhesives), it is becoming important to understand what properties
of lignin are required to impart key features in the final product.
Commercial lignins are complex, heterogeneous, macromolecular mixtures.
To obtain maximum value, lignins will require classification and possibly
fractionation or modification to improve properties and enable their
utilization in high-value applications. To this end, the physicochemical
properties of fractions derived from two industrial softwood Kraft
lignins (New Bern Mill, Weyerhaeuser, U.S.A., and Backhammar Mill
in Kristinehamn, Sweden) have been determined and compared to previously
published data on commercially available Indulin AT lignin from MeadWestvaco., The fractions were obtained by successive extraction with organic
solvents and analyzed using a range of techniques (e.g., DSC, <sup>13</sup>C NMR, <sup>31</sup>P NMR). The results showed that these
industrial softwood Kraft lignins varied significantly in both the
amounts of the various fractions and in the properties of the analogous
fractions. These differences emphasize the issues industry faces in
the utilization of industrial lignins for high-value applications
where minor inconsistencies between lignin sources could pose major
technical challenges