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Rapeseed straw polymeric hemicelluloses obtained by extraction methods based on severity factor
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.ORCID iD: 0000-0002-2041-5786
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-8992-3623
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-1631-1781
2017 (English)In: INDUSTRIAL CROPS AND PRODUCTS, ISSN 0926-6690, Vol. 95, p. 305-315Article in journal (Refereed) Published
Abstract [en]

Rapeseed straw consists of a hard epidermis that is rich in hemicellulose and lignin and a sponge-like interior that consists mainly of cellulose. The stems were subjected to water, alkali or acid as extraction medium. The effects of the extraction conditions were quantified using severity factors and by comparing the effects of different extraction pHs, temperatures and times. Extraction with alkali resulted in a higher yield, 47 g/100 g straw in, compared to water, 6 g/100 g straw in, or an acidic, 5 g/100 g straw in, extraction process. An increase in temperature improved the extraction yield; in particular, more xylan was extracted at an elevated temperature and higher alkalinity. However, at high alkalinity, increased extraction temperatures led to a reduction in the recovery of glucomannan. The highest molecular weights (similar to 35,000 g/mol) of the extracted hemicelluloses were obtained using extraction procedures with 1.5 M NaOH at 110 degrees C and autohydrolysis at 150 degrees C. While these two parameter settings had very similar severity factors, extraction under basic conditions afforded an extract rich in xylan and low in lignin content, whereas autohydrolysis generated a glucomannan-rich extract.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 95, p. 305-315
Keywords [en]
Rapeseed/canola straw, Extraction, Autohydrolysis, Severity factor, Hemicellulose
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-200198DOI: 10.1016/j.indcrop.2016.10.038ISI: 000390621600035Scopus ID: 2-s2.0-85004143297OAI: oai:DiVA.org:kth-200198DiVA, id: diva2:1070850
Note

QC 20170202

Available from: 2017-02-02 Created: 2017-01-23 Last updated: 2018-09-07Bibliographically approved
In thesis
1. Biopolymers and materials from rapeseed straw biorefining
Open this publication in new window or tab >>Biopolymers and materials from rapeseed straw biorefining
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rapeseed straw was fractionated through a hydrothermal process into its hemicellulose, lignin and cellulose components. In the first step, hemicellulose-rich fractions were extracted. Xylan-rich fractions with high molecular weight, 30,000 – 50,000 g/mol, were obtained at 110 °C and 1.5 M NaOH. Neutral and acidic conditions yielded extract rich in glucomannan with co-extracted xylan and lignin.After hemicellulose extraction, the straw was subjected to a soda cooking step where the straw was delignified and lignin solubilized. Two cooking times were evaluated in this step. A longer cooking time resulted in a lignin-rich precipitate and a cellulose pulp with a lower content of lignin compared with the shorter cooking time. Analysis showed rapeseed straw lignin consists of syringyl and guaiacyl aromatic structures. Peroxide bleaching of the pulp decreased the lignin content in the cellulose pulp further. Cellulose nanoparticles (CNF and CNC) were isolated from the bleached pulp. The CNF fraction was heterogenous in size while the CNC fraction was more homogenous in size with rod like aspects. Both were highly crystalline, with good thermal stability and high aspect ratio.Thin free-standing films of xylan were cast from water solution with mechanical integrity and very high strain-at-break > 80% even without added plasticizer.A surface modification process was developed where xylan was first pre-activated in alkali. This was followed by an etherification coupling reaction with glycidyl methacrylate and subsequently grafted by interfacial free radical graft polymerization with octadecyl acrylate chains. The resulting grafted xylan became hydrophobic and gained a thermoplastic behavior. It was blended with PCL matrix via melt-extrusion. The grafted xylan was homogeneously distributed within the biocomposite and the PCL matrix was reinforced while at the same time preserving the ability to elongate to tensile strains > 500%. Analogous biocomposites with unmodified xylan in a PCL matrix resulted in heterogenous mixtures and brittle tensile properties.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2018. p. 89
Series
TRITA-CBH-FOU ; 2018:38
Keywords
Rapeseed/canola straw, biorefinery, hemicelluloses, lignin, cellulose, cellulose nanoparticles, films, grafting, thermoplastic, biocomposites, rapshalm, bioraffinaderi, hemicellulosa, lignin, cellulosa, cellulosa nano partiklar, hemicellulosafilm, ympning, termoplastisk, biokompositer
National Category
Polymer Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-234656 (URN)978-91-7729-913-4 (ISBN)
Public defence
2018-10-12, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180912

Available from: 2018-09-12 Created: 2018-09-07 Last updated: 2018-09-12Bibliographically approved

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Svärd, AntoniaBrännvall, ElisabetEdlund, Ulrica

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