Molecular weight and molecular weight distribution of kraft lignins
- Univ. of Florida, Gainesville, FL (United States)
Kraft lignins are the lignin degradation products from kraft pulping. They are complex, heterogeneous polymers with some polar character. The molecular weight of kraft lignins greatly affect the physical properties of black liquors, and are of primary importance in separation from black liquor and in evaluating potential uses. Several purified kraft lignins from slash pine were analyzed for number average molecular weight by vapor pressure osmometry (VPO), for weight average molecular weight by low angle laser light scattering (LALLS), and for the molecular weight distribution by high temperature size exclusion chromatography (SEC). The lignins were run in tetrahydrofuran (THF), N,N-dimethyl formamide (DMF), DMF with 0.1M LiBr, and pyridine at conditions above the Theta temperature. Experimental methods are discussed. The results show that VPO may be used to determine M[sub n] for kraft lignins if the purity of the lignins and the identity of the impurities are known. LALLS can be used to determine M[sub w] for kraft lignins if measurements are made at or above the Theta temperature of the lignin-solvent pair. SEC should be used at temperatures at, or above, the Theta temperature of the lignin-solvent pair. Size separation is highly dependent on the solvent used, and DMF is a much better solvent than THF for high temperature SEC. Future work using moment resolution procedures to derive an accurate calibration curve are also discussed.
- DOE Contract Number:
- FG02-85CE40740
- OSTI ID:
- 5526861
- Report Number(s):
- CONF-900466-; CODEN: MRSPDH
- Journal Information:
- Materials Research Society Symposia Proceedings; (United States), Vol. 197; Conference: Spring meeting of the Materials Research Society (MRS), San Francisco, CA (United States), 16-21 Apr 1990; ISSN 0272-9172
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
LIGNIN
DISSOCIATION
ORGANIC POLYMERS
MOLECULAR WEIGHT
DISTRIBUTION
LASER SPECTROSCOPY
LIQUID COLUMN CHROMATOGRAPHY
OSMOSIS
PINES
CARBOHYDRATES
CHROMATOGRAPHY
CONIFERS
DIFFUSION
ORGANIC COMPOUNDS
PINOPHYTA
PLANTS
POLYMERS
POLYSACCHARIDES
SACCHARIDES
SEPARATION PROCESSES
SPECTROSCOPY
TREES
400102* - Chemical & Spectral Procedures
400105 - Separation Procedures