Tailoring the Molecular and Thermo-Mechanical Properties of Kraft Lignin by Ultrafiltration
2014 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 18, 9505-9515 p.Article in journal (Refereed) Published
This study has shown that ultrafiltration allows the selective extraction from industrial black liquors of lignin fraction with specific thermo-mechanical properties, which can be matched to the intended end uses. Ultrafiltration resulted in the efficient fractionation of kraft lignin according to its molecular weight, with an accumulation of sulfur-containing compounds in the low-molecular weight fractions. The obtained lignin samples had a varying quantities of functional groups, which correlated with their molecular weight with decreased molecular size, the lignin fractions had a higher amount of phenolic hydroxyl groups and fewer aliphatic hydroxyl groups. Depending on the molecular weight, glass-transition temperatures (T-g) between 70 and 170 degrees C were obtained for lignin samples isolated from the same batch of black liquor, a tendency confirmed by two independent methods, DSC, and dynamic rheology (DMA). The Fox-Flory equation adequately described the relationship between the number average molecular masses (M-n) and T-g's-irrespective of the method applied. DMA showed that low-molecular-weight lignin exhibits a good flow behavior as well as high-temperature crosslinking capability. Unfractionated and high molecular weight lignin (M-w > 5 kDa), on the other hand, do not soften sufficiently and may require additional modifications for use in thermal processings where melt-flow is required as the first step.
Place, publisher, year, edition, pages
2014. Vol. 131, no 18, 9505-9515 p.
biopolymers and renewable polymers, crosslinking, glass transition, rheology, thermal properties
IdentifiersURN: urn:nbn:se:kth:diva-143949DOI: 10.1002/app.40799ISI: 000337623600057ScopusID: 2-s2.0-84902544032OAI: oai:DiVA.org:kth-143949DiVA: diva2:709862
QC 20140806. Updated from manuscript to article in journal.2014-04-032014-04-032014-08-06Bibliographically approved