Change search
ReferencesLink to record
Permanent link

Direct link
Cellulose degradation in pulp fibers studied as changes in molar mass distributions
KTH, Superseded Departments, Fibre and Polymer Technology.
2003 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

In this thesis, size-exclusion chromatography (SEC) of woodpolymers dissolved in lithium chloride/N,N-dimethylacetamide(LiCl/DMAc) has been used to characterize the molar massdistributions (MMD) of wood polymers in pulp fibers afterchemical degradation.

Characterization of birch kraft pulps subjected to ozonedegradation and acid hydrolysis, respectively, rendereddifferent changes in the MMD. Ozone degradation resulted inlarge redistributions of the original MMD, observed as thedevelopment of a distinct fraction of cellulose withintermediate molar mass. Acid hydrolysis resulted in minorchanges of the original MMD compared to ozonation. Fiberssubjected to acid hydrolysis were considerably weaker thanozonated fibers. These results indicated that there aredifferences in how the two chemicals degrade the fiber.

The solubility of softwood kraft pulp fibers was enhanced byderivatization of the fiber polymers with ethyl-isocyanateduring simultaneous dissolution in LiCl/DMAc. Thederivatization made it possible to achieve reliable estimationsof the MMD, and hence molar masses, of softwood kraft pulps.The derivatization procedure made it possible to dissolve 90 %of softwood kraft pulps with kappa numbers over 50.

Severe alkaline degradation of birch and Norway spruce woodchips was studied both by varying the pulping time and byvarying the initial alkali concentration. Differences werefound in the MMD of the two fiber types, and the alkalinedegradation was found to affect polymers in the entire MMD.

Multi-angular laser light scattering (MALLS) was used as adetection technique with SEC on cellulosic samples. The MMD andaverage molar masses obtained through directstandardcalibration with commercial standards were compared with MMDand molar masses as obtained by MALLS-detection. Largediscrepancies were found, and two methods of correcting forthese discrepancies were developed.

Theoretical simulations of polymer degradation wereperformed. Random, or homogeneous degradation was used as amodel for alkaline cellulose chain scission, and a resemblancewith experimental data was observed. End-wise depolymerizationof cellulose was also simulated and the results are discussedin the light of experimentally observed MMD.

Keywords:cellulose, kraft pulp, birch, spruce,ozonation, acid hydrolysis, degradation, MMD, sizeexclusionchromatography, light scattering, molar mass, chainscission

Place, publisher, year, edition, pages
Stockholm: Fiber- och polymerteknologi , 2003. , 81 p.
Trita-PMT, 2003:4
Keyword [en]
cellulose, kraft pulp, birch, spruce, ozonation, acid hydrolysis, degradation, MMD, size-exclusion chromatography, light scattering, molar mass, chain scission
URN: urn:nbn:se:kth:diva-3499ISBN: OAI: diva2:9304
Public defence
NR 20140805Available from: 2003-04-15 Created: 2003-04-15Bibliographically approved

Open Access in DiVA

fulltext(836 kB)7632 downloads
File information
File name FULLTEXT01.pdfFile size 836 kBChecksum SHA-1
Type fulltextMimetype application/pdf

By organisation
Fibre and Polymer Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 7632 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 775 hits
ReferencesLink to record
Permanent link

Direct link