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Dissolution of softwood kraft pulps by direct derivatization in lithium chloride/ N , N ‐dimethylacetamide
Author(s) -
Berthold Fredrik,
Gustafsson Kristina,
Berggren Rickard,
Sjöholm Elisabeth,
Lindström Mikael
Publication year - 2004
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.20697
Subject(s) - softwood , derivatization , kraft paper , hardwood , kraft process , chemistry , lignin , chromatography , dimethylacetamide , cellulose , dissolution , isocyanate , pulp (tooth) , materials science , organic chemistry , high performance liquid chromatography , composite material , solvent , botany , medicine , pathology , polyurethane , biology
A method for the characterization of the molar mass distributions (MMDs) of softwood kraft pulps dissolved in 0.5% lithium chloride (LiCl)/ N , N ‐dimethylacetamide (DMAc) by size exclusion chromatography is presented. The method is based on derivatization with ethyl isocyanate and the dissolution of samples in 8% LiCl/DMAc. In this study, the derivatization of hardwood kraft pulps did not influence the MMD. In the case of softwood pulps, however, the derivatization decreased the proportion of the high‐molecular‐mass material and increased the proportion of the low‐molecular‐mass material, which resulted in a distribution similar to the MMD of a hardwood kraft pulp. The results suggest that associations between hemicellulose and cellulose in the softwood kraft pulp were ruptured during derivatization. This led to a more correct estimation of the MMD of derivatized softwood kraft pulps than obtained by the dissolution of nonderivatized samples. This new method offers several advantages over derivatization with phenyl isocyanate: a precipitation step is not necessary, it is possible to follow the lignin distribution in the samples, and the method allows very high levels of dissolution of softwood kraft pulps up to a κ number of around 50. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 424–431, 2004