Birch xylan grafted with pla branches of predictable length
2012 (English)In: BioResources, ISSN 1930-2126, Vol. 7, no 3, 3640-3655 p.Article in journal (Refereed) Published
Birch xylan (4-O-methylglucuronoxylan) isolated from a kraft cooking liquor was delignified and grafted with polylactide of predictable branch length. This graft copolymerization resulted in very high total yields, greater than 90%, and with less than 10% polylactide homopolymer byproducts. Mild reaction conditions (40 degrees C, 5 to 120 minutes) were used, which was believed to limit transesterification reactions and thus make it possible to reach good predictability of the polylactide branch length. The thermal properties of the polylactide-grafted xylan depended on the branch length. Short branches resulted in fully amorphous materials with a glass transition temperature of about 48 to 55 degrees C, whereas long polylactide branches resulted in semi-crystalline materials with melting points of about 130 degrees C. Using mixtures of L-lactide and D/L-lactide in the monomer feed further altered the thermal properties. The degradation temperatures of the polylactide-grafted xylans were higher than that of the unmodified xylan, with degradation temperatures of about 300 degrees C and 250 degrees C, respectively. Tensile testing showed increased elongation at break with increasing branch length. The proposed method thus enables tailor-making of copolymers with specific thermal and mechanical properties.
Place, publisher, year, edition, pages
2012. Vol. 7, no 3, 3640-3655 p.
Hemicellulose, Xylan, Grafting, Lactide, ROP, Glass transition, Melt transition; Tensile strength
IdentifiersURN: urn:nbn:se:kth:diva-93970ISI: 000307639900073ScopusID: 2-s2.0-84865748399OAI: oai:DiVA.org:kth-93970DiVA: diva2:524693
QC 20120924. Updated from manuscript to article in journal.2012-05-032012-05-032012-09-24Bibliographically approved