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Nissilä, T., Oksman, K. & Hietala, M. (2019). A method for preparing epoxy-cellulose nanofiber composites with an oriented structure. Composites. Part A, Applied science and manufacturing, 125, Article ID 105515.
Open this publication in new window or tab >>A method for preparing epoxy-cellulose nanofiber composites with an oriented structure
2019 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 125, article id 105515Article in journal (Refereed) Published
Abstract [en]

A method was developed for processing cellulose nanocomposites using conventional vacuum infusion. Porouscellulose nanofiber networks were prepared via ice-templating and used as preforms for impregnation with a bioepoxyresin. Microscopy studies showed a unidirectionally oriented micrometer-scale pore structure that facilitatedthe infusion process by providing flow channels for the resin. The permeability of the preforms wascomparable to that of natural fiber mats, and the infusion time significantly decreased after optimizing theprocessing temperature. The flexural modulus of the bio-epoxy increased from 2.5 to 4.4 GPa, the strengthincreased from 89 to 107 MPa, and the storage modulus increased from 2.8 to 4.2 GPa with 13 vol% cellulosenanofibers. The mechanical properties also showed anisotropy, as the flexural and storage moduli were approximately25% higher in the longitudinal direction, indicating that the nanofiber network inside the epoxymatrix had an oriented nature.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Cellulose, Nanocomposites, Mechanical properties, Vacuum infusion
National Category
Engineering and Technology Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-75412 (URN)10.1016/j.compositesa.2019.105515 (DOI)000484878200001 ()2-s2.0-85068541264 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-13 (johcin)

Available from: 2019-08-06 Created: 2019-08-06 Last updated: 2019-09-27Bibliographically approved
Singh, S., Maspoch, M. L. & Oksman, K. (2019). Crystallization of triethyl-citrate-plasticized poly(lactic acid) induced by chitin nanocrystals. Journal of Applied Polymer Science, 136(36), Article ID 47936.
Open this publication in new window or tab >>Crystallization of triethyl-citrate-plasticized poly(lactic acid) induced by chitin nanocrystals
2019 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 136, no 36, article id 47936Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to gain a better understanding of the crystallization behavior of triethyl-citrate-plasticizedpoly(lactic acid) (PLA–TEC) in the presence of chitin nanocrystals (ChNCs). The isothermal crystallization behavior of PLA–TEC wasstudied by polarized optical microscopy, scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction (XRD).Interestingly, the addition of just 1 wt % ChNCs in PLA–TEC increased the crystallization rate in the temperature range of 135–125 C.The microscopy studies confirmed the presence of at least three distinct types of spherulites: negative, neutral, and ring banded. TheChNCs also increased the degree of crystallinity up to 32%, even at a fast cooling rate of 25 C min−1. The XRD studies further revealedthe nucleation effect induced by the addition of ChNCs and thus explained the faster crystallization rate. To conclude, the addition of asmall amount (1 wt %) of ChNC to plasticized PLA significantly affected its nucleation, crystal size, and crystallization speed; therefore,the proposed route can be considered suitable for improving the crystallization behavior of PLA. 

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
chitin nanocrystals, isothermal crystallization, microstructure, plasticizer, poly(lactic acid)
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-73964 (URN)10.1002/APP.47936 (DOI)000471755000019 ()2-s2.0-85065669156 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-25 (johcin)

Available from: 2019-05-15 Created: 2019-05-15 Last updated: 2019-07-10Bibliographically approved
Hassan, M., Zeid, R. E. A., Abou-Elseoud, W. S., Hassan, E., Berglund, L. & Oksman, K. (2019). Effect of Unbleached Rice Straw Cellulose Nanofibers on the Properties of Polysulfone Membranes. Polymers, 11(6), Article ID 938.
Open this publication in new window or tab >>Effect of Unbleached Rice Straw Cellulose Nanofibers on the Properties of Polysulfone Membranes
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2019 (English)In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, no 6, article id 938Article in journal (Refereed) Published
Abstract [en]

In addition to their lower cost and more environmentally friendly nature, cellulose nanofibers isolated from unbleached pulps offer different surface properties and functionality than those isolated from bleached pulps. At the same time, nanofibers isolated from unbleached pulps keep interesting properties such as hydrophilicity and mechanical strength, close to those isolated from bleached pulps. In the current work, rice straw nanofibers (RSNF) isolated from unbleached neutral sulfite pulp (lignin content 14%) were used with polysulfone (PSF) polymer to make membrane via phase inversion. The effect of RSNF on microstructure, porosity, hydrophilicity, mechanical properties, water flux, and fouling of PSF membranes was studied. In addition, the prepared membranes were tested to remove lime nanoparticles, an example of medium-size nanoparticles. The results showed that using RSNF at loadings from 0.5 to 2 wt.% can significantly increase hydrophilicity, porosity, water flux, and antifouling properties of PSF. RSNF also brought about an increase in rejection of lime nanoparticles (up to 98% rejection) from their aqueous suspension, and at the same time, with increasing flux across the membranes. Tensile strength of the membranes improved by ~29% with addition of RSNF and the maximum improvement was obtained on using 0.5% of RSNF, while Young’s modulus improved by ~40% at the same RSNF loading. As compared to previous published results on using cellulose nanofibers isolated from bleached pulps, the obtained results in the current work showed potential application of nanofibers isolated from unbleached pulps for improving important properties of PSF membranes, such as hydrophilicity, water flux, rejection, and antifouling properties

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
rice straw, cellulose nanofibers, unbleached pulp, polysulfone, membrane
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-75163 (URN)10.3390/polym11060938 (DOI)000473819100010 ()31146496 (PubMedID)2-s2.0-85067339493 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-07-01 (johcin)

Available from: 2019-07-01 Created: 2019-07-01 Last updated: 2019-08-16Bibliographically approved
Singh, S., Rodriguez, C., Santana, O., Oksman, K. & Maspoch, M. (2019). Evaluation of mechanical properties of poly(lactic acid)/cellulose nanocrystal nanocomposites: A comparative study of conventional tensile test and small punch test. In: : . Paper presented at 36th Conference of the Spanish Group of Fracture, (GEF) 2019,Sivilla, Spain, 3-5 April, 2019.
Open this publication in new window or tab >>Evaluation of mechanical properties of poly(lactic acid)/cellulose nanocrystal nanocomposites: A comparative study of conventional tensile test and small punch test
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2019 (English)Conference paper, Oral presentation with published abstract (Refereed) [Artistic work]
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ltu:diva-73395 (URN)
Conference
36th Conference of the Spanish Group of Fracture, (GEF) 2019,Sivilla, Spain, 3-5 April, 2019
Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-04-02
Ghafari, R., Jonoobi, M., Mohammadi Amirabad, L., Oksman, K. & Taheri, A. R. (2019). Fabrication and characterization of novel bilayer scaffold from nanocellulose based aerogel for skin tissue engineering applications. International Journal of Biological Macromolecules, 136, 796-803
Open this publication in new window or tab >>Fabrication and characterization of novel bilayer scaffold from nanocellulose based aerogel for skin tissue engineering applications
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2019 (English)In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 136, p. 796-803Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to fabricate a novel bilayer scaffold containing cellulose nanofiber/poly (vinyl) alcohol (CNF/PVA) to evaluate its potential use in skin tissue engineering. Here, the scaffolds were fabricated using a novel one-step freeze-drying technique with two different concentrations of the aforementioned polymers. FE-SEM analysis indicated that the fabricated scaffolds had interconnected pores with two defined pore size in each layer of the bilayer scaffolds that can recapitulate the two layers of the dermis and epidermis of the skin. Lower concentration of polymers causes higher porosity with larger pore size and increased water uptake and decreased mechanical strength. FTIR proved the presence of functional groups and strong hydrogen bonding between the molecules of CNF/PVA and the efficient crosslinking. The MTT assay showed that these nanofibrous scaffolds meet the requirement as a biocompatible material for skin repair. Here, for the first time, we fabricated bilayer scaffold using a novel one-step freeze-drying technique only by controlling the polymer concentration with spending less time and energy.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Bilayered scaffold, Cellulose nanofiber (CNF), Freeze-drying, Skin tissue engineering
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-75120 (URN)10.1016/j.ijbiomac.2019.06.104 (DOI)000482533000080 ()31226370 (PubMedID)2-s2.0-85067698284 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-28 (svasva)

Available from: 2019-06-28 Created: 2019-06-28 Last updated: 2019-09-13Bibliographically approved
Jonasson, S., Bünder, A., Niittylä, T. & Oksman, K. (2019). Isolation and characterization of cellulose nanofibers from aspen wood using derivatizing and non-derivatizing pretreatments. Cellulose (London)
Open this publication in new window or tab >>Isolation and characterization of cellulose nanofibers from aspen wood using derivatizing and non-derivatizing pretreatments
2019 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed) Epub ahead of print
Abstract [en]

The link between wood and corresponding cellulose nanofiber (CNF) behavior is complex owing the multiple chemical pretreatments required for successful preparation. In this study we apply a few pretreatments on aspen wood and compare the final CNF behavior in order to rationalize quantitative studies of CNFs derived from aspen wood with variable properties. This is relevant for efforts to improve the properties of woody biomass through tree breeding. Three different types of pretreatments were applied prior to disintegration (microfluidizer) after a mild pulping step; derivatizing TEMPO-oxidation, carboxymethylation and non-derivatizing soaking in deep-eutectic solvents. TEMPO-oxidation was also performed directly on the plain wood powder without pulping. Obtained CNFs (44–55% yield) had hemicellulose content between 8 and 26 wt% and were characterized primarily by fine (height ≈ 2 nm) and coarser (2 nm < height < 100 nm) grade CNFs from the derivatizing and non-derivatizing treatments, respectively. Nanopapers from non-derivatized CNFs had higher thermal stability (280 °C) compared to carboxymethylated (260 °C) and TEMPO-oxidized (220 °C). Stiffness of nanopapers made from non-derivatized treatments was higher whilst having less tensile strength and elongation-at-break than those made from derivatized CNFs. The direct TEMPO-oxidized CNFs and nanopapers were furthermore morphologically and mechanically indistinguishable from those that also underwent a pulping step. The results show that utilizing both derivatizing and non-derivatizing pretreatments can facilitate studies of the relationship between wood properties and final CNF behavior. This can be valuable when studying engineered trees for the purpose of decreasing resource consumption when isolation cellulose nanomaterials.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Nanofibrillation, Cellulose nanofiber, Nanopaper, TEMPO-oxidation, Deep-eutectic solvents, Carboxymethylation
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-76315 (URN)10.1007/s10570-019-02754-w (DOI)000488917400002 ()
Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2019-10-18
Kumar, M., Hietala, M. & Oksman, K. (2019). Lignin-Based Electrospun Carbon Nanofibers. Frontiers in Materials, 6, Article ID 62.
Open this publication in new window or tab >>Lignin-Based Electrospun Carbon Nanofibers
2019 (English)In: Frontiers in Materials, E-ISSN 2296-8016, Vol. 6, article id 62Article in journal (Refereed) Published
Abstract [en]

The article summarizes the scientific progress that has occurred in the past several years in regard to the preparation of carbon nanofibers from lignin as a low-cost environmentally-friendly raw material using electrospinning. It presents an overview of using lignin, electrospinning, and carbonization to convert lignin to carbon nanofibers. Lignin is a renewable source for carbon material, and it is very abundant in nature. It is mostly produced as a byproduct from the paper industry and biomass fractionation. Despite its extensive availability and beneficial properties, only a few studies have reported on its use in electronic applications. Lignin-based carbon nanofibers have a high surface area, high porosity, and good electrical conductivity; thus, it is proposed that they are suitable for future energy storage applications.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
lignin, electrospinning, carbonization, carbon nanofibers, energy storage
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-73726 (URN)10.3389/fmats.2019.00062 (DOI)000464304300001 ()2-s2.0-85067383932 (Scopus ID)
Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2019-07-09Bibliographically approved
Kusano, Y., Madsen, B., Berglund, L. & Oksman, K. (2019). Modification of cellulose nanofibre surfaces by He/NH3 plasma at atmospheric pressure. Cellulose (London), 26(12), 7185-7194
Open this publication in new window or tab >>Modification of cellulose nanofibre surfaces by He/NH3 plasma at atmospheric pressure
2019 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 12, p. 7185-7194Article in journal (Refereed) Published
Abstract [en]

Cellulose nanofibre coatings were treated by a dielectric barrier discharge plasma in a He/NH3 gas mixture at atmospheric pressure. Ultrasound was optionally irradiated during the treatment. The treatment enhanced the wetting of deionized water, glycerol, and uncured epoxy. Irradiation of ultrasound did not significantly change optical emission from the plasma, but increased the oxygen contents and enhanced etching and roughening at the nanofibre coating surfaces. Furthermore, the irradiation of ultrasound enhanced the wetting of deionized water and glycerol drastically, while that of uncured epoxy to some extent.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Cellulose, Nanofibre, Plasma treatment, Dielectric barrier discharge, Ultrasound, Wetting, Surface roughening
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-75355 (URN)10.1007/s10570-019-02594-8 (DOI)000477863700013 ()2-s2.0-85068879659 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-20 (johcin)

Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-08-22Bibliographically approved
Hassan, M., Berglund, L., Abou-Zeid, R., Hassan, E., Abou-Elseoud, W. & Oksman, K. (2019). Nanocomposite Film Based on Cellulose Acetate and Lignin-Rich Rice Straw Nanofibers. Materials, 12(4), Article ID 595.
Open this publication in new window or tab >>Nanocomposite Film Based on Cellulose Acetate and Lignin-Rich Rice Straw Nanofibers
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 4, article id 595Article in journal (Refereed) Published
Abstract [en]

Nanofibers isolated from unbleached neutral sulfite rice straw pulp were used to prepare transparent films without the need to modify the isolated rice straw nanofibers (RSNF). RSNF with loading from 1.25 to 10 wt.% were mixed with cellulose acetate (CA) solution in acetone and films were formed by casting. The films were characterized regarding their transparency and light transmittance, microstructure, mechanical properties, crystallinity, water contact angle, porosity, water vapor permeability, and thermal properties. The results showed good dispersion of RSNF in CA matrix and films with good transparency and homogeneity could be prepared at RSNF loadings of less than 5%. As shown from contact angle and atomic force microscopy (AFM) measurements, the RSNF resulted in increased hydrophilic nature and roughness of the films. No significant improvement in tensile strength and Young’s modulus was recorded as a result of adding RSNF to CA. Addition of the RSNF did not significantly affect the porosity, crystallinity and melting temperature of CA, but slightly increased its glass transition temperature

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
nanofibers, rice straw, unbleached pulp, cellulose acetate, nanocomposites
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-73036 (URN)10.3390/ma12040595 (DOI)000460793300045 ()30781531 (PubMedID)2-s2.0-85061647725 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-27 (johcin)

Available from: 2019-02-27 Created: 2019-02-27 Last updated: 2019-04-12Bibliographically approved
Wei, J., Geng, S., Sarmad, S., Hedlund, J. & Oksman, K. (2018). Adsorption of Carbon Dioxide on Cellulose Nanofiber-Based Monolithic Cryogels Impregnated with Acetylated Cellulose Nanocrystals. In: : . Paper presented at 72nd Forest Products Society (FPS) International Convention, Madison, Wisconsin, USA, June 11–14, 2018.
Open this publication in new window or tab >>Adsorption of Carbon Dioxide on Cellulose Nanofiber-Based Monolithic Cryogels Impregnated with Acetylated Cellulose Nanocrystals
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2018 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Nanocellulose materials with large surface area are prospective as substrates to obtain low-carbon-footprint CO2 adsorbents. In this study, ice-templating was conducted to prepare cellulose nanofibers (CNFs) based cryogels with monolithic structure, which can provide a good mass flow during the adsorption process. Furthermore, since acetyl groups have shown relatively high CO2 affinity, cellulose nanocrystals (CNCs) were acetylated and then impregnated into the cryogel to improve its CO2 capacity. Meanwhile, different amounts of cellulose acetate (CA) were impregnated and characterized as references. The success of the acetylation of CNCs was confirmed by Fourier-transform infrared spectroscopy (FTIR) and the degree of substitution was determined by titration. Results from the scanning electron microscopy (SEM) demonstrated that the monolithic structure was maintained after the impregnation. According to the breakthrough test, the cryogel impregnated with 0.1g of acetylated CNCs exhibits a much higher CO2 capacity with a value of 1.49 mmol/g compared to the CA impregnated ones. The mechanical properties of the cryogels were also evaluated by compression testing, revealing the outstanding reinforcing effect of acetylated CNCs.

Keywords
Nanocellulose, cryogel, adsorption, carbon dioxide, acetylation
National Category
Chemical Process Engineering Bio Materials
Research subject
Wood and Bionanocomposites; Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-71083 (URN)
Conference
72nd Forest Products Society (FPS) International Convention, Madison, Wisconsin, USA, June 11–14, 2018
Available from: 2018-10-02 Created: 2018-10-02 Last updated: 2019-01-16Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4762-2854

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