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Publications (10 of 21) Show all publications
Huang, T., Chen, C., Li, D. & Ek, M. (2019). Hydrophobic and antibacterial textile fibres prepared by covalently attaching betulin to cellulose. Paper presented at National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL. Abstracts of Papers of the American Chemical Society, 257
Open this publication in new window or tab >>Hydrophobic and antibacterial textile fibres prepared by covalently attaching betulin to cellulose
2019 (English)In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-257602 (URN)000478860503101 ()
Conference
National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL
Note

QC 20190919

Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-19Bibliographically approved
Huang, T., Chen, C., Li, D. & Ek, M. (2019). Hydrophobic and antibacterial textile fibres prepared by covalently attaching betulin to cellulose. Cellulose (London), 26(1), 665-677
Open this publication in new window or tab >>Hydrophobic and antibacterial textile fibres prepared by covalently attaching betulin to cellulose
2019 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 1, p. 665-677Article in journal (Refereed) Published
Abstract [en]

Betulin, a natural compound extractable from the outer bark of birch, can be used to improve the properties of cellulosic textile fibres. Herein, oxidation was performed to prepare carboxyl-functionalized cellulose, which was subsequently covalently attached by betulin through esterification. The surface-modified cellulosic textile fibres showed a substantially improved hydrophobicity, as indicated by a water contact angle of 136°. Moreover, the material showed excellent antibacterial properties, as indicated by over 99% bacterial removal and growth inhibition, in both Gram-positive and Gram-negative bacterial assays. The method of surface-modification of the cellulosic materials adapted in this study is simple and, to the best of our knowledge, has not been carried out before. The results of this study prove that betulin, a side-stream product produced by forest industry, could be used in value-added applications, such as for preparing functional materials. Additionally, this modification route can be envisaged to be applied to other cellulose sources (e.g., microfibrillated cellulose) to achieve the goal of functionalization.

Place, publisher, year, edition, pages
Springer Netherlands, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-243083 (URN)10.1007/s10570-019-02265-8 (DOI)000458742600037 ()2-s2.0-85060491197 (Scopus ID)
Note

QC 20190205

Available from: 2019-02-04 Created: 2019-02-04 Last updated: 2019-10-17Bibliographically approved
Zheng, C., Li, D. & Ek, M. (2019). Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants. Nordic Pulp & Paper Research Journal, 34(1), 96-106
Open this publication in new window or tab >>Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants
2019 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 34, no 1, p. 96-106Article in journal (Refereed) Published
Abstract [en]

Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m(2). Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m(2), as shown by cone calorimetry and single-flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications for improving fire retardancy of sustainable thermal insulating materials.

Place, publisher, year, edition, pages
AB SVENSK PAPPERSTIDNING, 2019
Keywords
bio-based, cellulose, coating, fire retardant, thermal insulating material
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-246233 (URN)10.1515/npprj-2018-0031 (DOI)000460119600011 ()2-s2.0-85061101260 (Scopus ID)
Note

QC 20190403

Available from: 2019-04-03 Created: 2019-04-03 Last updated: 2019-04-03Bibliographically approved
Zheng, C., Li, D. & Ek, M. (2019). Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants. Journal of thermal analysis and calorimetry (Print), 135(6), 3015-3027
Open this publication in new window or tab >>Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants
2019 (English)In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 135, no 6, p. 3015-3027Article in journal (Refereed) Published
Abstract [en]

The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (Ea).The increased Ea indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased Ea after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the Ea of fire-retarded cellulose thermal insulation compared with the KAS and two methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

Place, publisher, year, edition, pages
Springer Netherlands, 2019
Keywords
Thermal degradation, Thermal kinetics, Fire retardant, Cellulose fiber, Thermal insulating
National Category
Paper, Pulp and Fiber Technology Wood Science
Identifiers
urn:nbn:se:kth:diva-233485 (URN)10.1007/s10973-018-7564-5 (DOI)000462553400011 ()2-s2.0-85050669625 (Scopus ID)
Funder
Swedish Research Council Formas
Note

QC 20180821

Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2019-08-27Bibliographically approved
Henschen, J., Li, D. & Ek, M. (2019). Preparation of cellulose nanomaterials via cellulose oxalates. Carbohydrate Polymers, 213, 208-216
Open this publication in new window or tab >>Preparation of cellulose nanomaterials via cellulose oxalates
2019 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 213, p. 208-216Article in journal (Refereed) Published
Abstract [en]

Nanocellulose prepared from cellulose oxalate has been discussed as an alternative to other methods to prepare cellulose nanofibrils or crystals. The current work describes the use of a bulk reaction between pulp and oxalic acid dihydrate to prepare cellulose oxalate followed by homogenization to produce nanocellulose. The prepared nanocellulose is on average 350 nm long and 3–4 nm wide, with particles of size and shape similar to both cellulose nanofibrils and cellulose nanocrystals. Films prepared from this nanocellulose have a maximum tensile stress of 140–200 MPa, strain at break between 3% and 5%, and oxygen permeability in the range of 0.3–0.5 cm 3 μm m −2 day −1 kPa −1 at 50% relative humidity. The presented results illustrate that cellulose oxalates may be a low-cost method to prepare nanocellulose with properties reminiscent of those of both cellulose nanofibrils and cellulose nanocrystals, which may open up new application areas for cellulose nanomaterials.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Cellulose, Cellulose nanocrystals, Cellulose nanofibrils, Cellulose oxalate, Nanocellulose, Oxalic acid dihydrate
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-246408 (URN)10.1016/j.carbpol.2019.02.056 (DOI)000461316200023 ()30879662 (PubMedID)2-s2.0-85062349488 (Scopus ID)
Note

QC 20190401

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-06-02Bibliographically approved
Guo, L., Li, D., Lennholm, H., Zhai, H. & Ek, M. (2019). Structural and functional modification of cellulose nanofibrils using graft copolymerization with glycidyl methacrylate by Fe 2+ –thiourea dioxide–H 2 O 2 redox system. Cellulose (London), 26(8), 4853-4864
Open this publication in new window or tab >>Structural and functional modification of cellulose nanofibrils using graft copolymerization with glycidyl methacrylate by Fe 2+ –thiourea dioxide–H 2 O 2 redox system
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2019 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 8, p. 4853-4864Article in journal (Refereed) Published
Abstract [en]

Abstract: To graft epoxy and ester functional groups onto cellulose nanofibrils (CNFs) and to overcome their poor hydrophobicity, we studied the modification of CNFs using graft copolymerization with glycidyl methacrylate (GMA) by a Fe 2+ –thiourea dioxide–H 2 O 2 initiator system (Fe 2+ –TD–H 2 O 2 ) in aqueous solution. The synthesized poly (GMA)-grafted CNF (CNF-g-PGMA) was characterized by FTIR, AFM, XRD, water contact angle, and TGA. GMA was successfully grafted onto the CNFs by Fe 2+ –TD–H 2 O 2 , the epoxy groups and ester groups of GMA were clearly present and intact in the CNF-g-PGMA, and TD is an important component of the initiator system under relatively mild graft conditions. CNF-g-PGMA may be an important intermediate because of its epoxy and ester functional groups. The main nanostructure of the CNFs was retained after graft copolymerization, and there were no obvious effects of graft copolymerization on the crystalline structure of the CNF backbone, although the crystalline index slightly decreased with the increased percentage of grafting. Graft copolymerization significantly modifies the CNF hydrophobicity. This strategy could extend the applications of CNFs into many areas. Graphical abstract: [Figure not available: see fulltext.]

Place, publisher, year, edition, pages
Springer Netherlands, 2019
Keywords
Cellulose nanofibrils, Fe 2+ –thiourea dioxide–H 2 O 2, Glycidyl methacrylate, Graft copolymerization, Modification
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-251818 (URN)10.1007/s10570-019-02411-2 (DOI)000467057500014 ()2-s2.0-85064689002 (Scopus ID)
Note

QC 20190529

Available from: 2019-05-29 Created: 2019-05-29 Last updated: 2019-05-29Bibliographically approved
Zheng, C., Li, D. & Ek, M. (2018). Bio-based fire retardant and its application in cellulose-based thermal insulation materials. Paper presented at 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, LA. Abstract of Papers of the American Chemical Society, 255
Open this publication in new window or tab >>Bio-based fire retardant and its application in cellulose-based thermal insulation materials
2018 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-240174 (URN)000435537703081 ()
Conference
255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, LA
Note

QC 20190111

Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-11Bibliographically approved
Huang, T., Li, D. & Ek, M. (2018). Water repellency improvement of cellulosic textile fibers by betulin and a betulin-based copolymer. Cellulose (London), 25(3), 2115-2128
Open this publication in new window or tab >>Water repellency improvement of cellulosic textile fibers by betulin and a betulin-based copolymer
2018 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 3, p. 2115-2128Article in journal (Refereed) Published
Abstract [en]

Betulin is a naturally abundant and hydrophobic compound in the outer bark of birch and can readily be obtained by solvent extraction. Here, solutions of betulin were used to treat cotton fabrics and improve their water repellency. Cotton fabric impregnated in a solution of betulin in ethanol showed a contact angle for water of approximately 153A degrees and reached a water repellency score of 70 according to a standard water repellency test method. A betulin-terephthaloyl chloride (TPC) copolymer was synthesized. Both betulin and betulin-TPC copolymer were characterized by nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The copolymer was characterized by size exclusion chromatography and differential scanning calorimetry. When impregnated with a solution of betulin-TPC copolymer in tetrahydrofuran, a cotton fabric showed a water contact angle of 151A degrees and also reached a water repellency score of 70. Films based on betulin and betulin-TPC copolymer were prepared and coated onto the surface of the fabrics by compression molding. These coated fabrics showed water contact angles of 123A degrees and 104A degrees respectively and each reached a water repellency score of 80.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Betulin, Cellulose, Contact angle, Copolymer, Textile, Water repellency
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-225201 (URN)10.1007/s10570-018-1695-5 (DOI)000427379200044 ()2-s2.0-85041537084 (Scopus ID)
Note

QC 20180403

Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2019-02-05Bibliographically approved
Ek, M., Li, D. & Henschen, J. (2017). Esterification and hydrolysis of cellulose using oxalic acid dihydrate in a solvent-free reaction suitable for preparation of surface-functionalised cellulose nanocrystals with high yield. Green Chemistry, 19, 5564-5567
Open this publication in new window or tab >>Esterification and hydrolysis of cellulose using oxalic acid dihydrate in a solvent-free reaction suitable for preparation of surface-functionalised cellulose nanocrystals with high yield
2017 (English)In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 19, p. 5564-5567Article in journal (Refereed) Published
Abstract [en]

A one-pot esterification and hydrolysis of cellulose was carried outby treating cellulose fibres with molten oxalic acid dihydrate. Eachcellulose oxalate had a free carboxyl content above 1.2 mmol g−1and an average molecular weight of approximately 40 kDa.Aqueous suspensions of the oxalates were sonicated to preparecellulose nanocrystals with a gravimetric yield of 80.6%

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Paper, Pulp and Fiber Technology
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-219967 (URN)10.1039/c7gc02489d (DOI)000417758700005 ()2-s2.0-85035811625 (Scopus ID)
Note

QC 20171218

Available from: 2017-12-14 Created: 2017-12-14 Last updated: 2019-06-05Bibliographically approved
Ek, M., Li, D. & Le Normand, M. (2016). WOBAMA wood based materials based on bark. Abstract of Papers of the American Chemical Society, 251
Open this publication in new window or tab >>WOBAMA wood based materials based on bark
2016 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-242672 (URN)000431903802553 ()
Note

QC 20190222

Available from: 2019-02-22 Created: 2019-02-22 Last updated: 2019-02-22Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7055-1057

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