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  • 301.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Aitomäki, Yvonne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Thermoplastic polymer impregnation of cellulose nanofibre networks: Morphology, mechanical and optical properties2014Inngår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 58, s. 30-35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biobased nanocomposite sheets of cellulose nanofibres (CNF) and cellulose acetate butyrate (CAB) were prepared using a resin impregnation technique. Porous nanofibre networks together with a low viscosity thermoplastic resin were the key elements in the processing. SEM images of the network before the impregnation showed high porosity and after the impregnation indicated impregnated fibre network. A significant improvement in the visible light transmittance was observed for the nanocomposite compared to the nanofibre network, which is explained on the filling of the pores with a transparent matrix. The tensile tests showed an increase of 364% and 145% for stiffness and strength respectively for nanocomposites with 60 wt.% CNF when compared to CAB. Dynamic mechanical properties showed a good interaction between the CAB and cellulose nanofibres. These results show that CAB impregnated cellulose nanofibre networks are promising biocomposite that could be used in applications where transparency and good mechanical properties are of interest.

  • 302.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Wood and Paper Sciences and Technology, Faculty of Natural ResourcesUniversity of Tehran.
    Ghorbani, Maryam
    Faculty of Natural Resources, Sari University of Agricultural Sciences and Natural Resources, Sari .
    Azarhazin, Ali
    Faculty of Natural Resources, Sari University of Agricultural Sciences and Natural Resources, Sari .
    Hosseinabadi, Hamid Zarea
    Department of Wood and Paper Sciences and Technology, Faculty of Natural Resources, University of Tehran.
    Effect of surface modification of fibers on the medium density fiberboard properties2018Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, nr 2, s. 517-524Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surface modification of mixed hardwoods fibers by sodium hydroxide (NaOH) was conducted to investigate the effect of chemical treatment on the fiber properties along with physico-mechanical characteristics of the medium density fiberboard (MDF). The results indicated that the NaOH treatments can dissolve a portion of hemicelluloses and almost all amount of extractives from the fibers, but it was not strong enough to remove the lignin thoroughly. The FTIR results illustrated that chemical changes can occur during the various NaOH treatments of the fibers. X-ray diffraction analysis revealed that the crystallinity of the studied fibers increased after the alkaline treatment. Investigation of mechanical properties of the MDF showed that modulus of rupture and internal bond strength of the treated samples were decreased compared to the control ones. In addition, water absorption and thickness swelling of treated boards were higher than that of untreated samples. This study indicated that the physico-mechanical properties of the boards were negatively affected by the NaOH treatment.

  • 303.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Harun, Jalaluddin
    Institute of Tropical Forestry and Forest Products, University Putra Malaysia, Kuala Lumpur.
    Mathew, Aji P.
    Hussein, Mohd ZB
    Department of Chemistry, Faculty of Science, University Putra Malaysia.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Preparation of cellulose nanofibers with hydrophobic surface characteristics2010Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, nr 2, s. 299-307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to develop cellulose nanofibers with hydrophobic surface characteristics using chemical modification. Kenaf fibers were modified using acetic anhydride and cellulose nanofibers were isolated from the acetylated kenaf using mechanical isolation methods. Fourier transform infrared spectroscopy (FTIR) indicated acetylation of the hydroxyl groups of cellulose. The study of the dispersion demonstrated that acetylated cellulose nanofibers formed stable, well-dispersed suspensions in both acetone and ethanol. The contact angle measurements showed that the surface characteristics of nanofibers were changed from hydrophilic to more hydrophobic when acetylated. The microscopy study showed that the acetylation caused a swelling of the kenaf fiber cell wall and that the diameters of isolated nanofibers were between 5 and 50 nm. X-ray analysis showed that the acetylation process reduced the crystallinity of the fibers, whereas mechanical isolation increased it. The method used provides a novel processing route for producing cellulose nanofibers with hydrophobic surfaces.

  • 304.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Harun, Jalaluddin
    University Putra Malaysia.
    Mathew, Aji P.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mechanical properties of cellulose nanofiber (CNF) reinforced polylactic acid (PLA) prepared by twin screw extrusion2010Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 70, nr 12, s. 1742-1747Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to develop cellulose nanofiber (CNF) reinforced polylactic acid (PLA) by twin screw extrusion. Nanocomposites were prepared by premixing a master batch with high concentration of CNFs in PLA and diluting to final concentrations (1, 3, 5 wt%) during the extrusion. Morphology, mechanical and dynamic mechanical properties (DMA) were studied theoretically and experimentally to see how different CNF concentrations affected the composites' properties. The tensile modulus and strength increased from 2.9 GPa to 3.6 GPa and from 58 MPa to 71 MPa, respectively, for nanocomposites with 5 wt% CNF. The DMA results were also positive; the storage modulus increased for all nanocomposites compared to PLA; being more significant in the high temperature region (70°C). The addition of nanofibers shifted the tan delta peak towards higher temperatures. The tan delta peak of the PLA shifted from 70°C to 76°C for composites with 5 wt% CNF.

  • 305.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Harun, Jalaludin
    University of Putra Malaysia.
    Mishra, Manju
    University of Guelph.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Chemical composition, crystallinity and thermal degradation of bleached and unbleached kenaf bast (Hibiscus cannabinus) pulp and nanofiber2009Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 4, nr 2, s. 626-639Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Kenaf (Hibiscus cannabinus) nanofibers were isolated from unbleached and bleached pulp by a combination of chemical and mechanical treatments. The chemical methods were based on NaOH-AQ (anthraquinone) and three-stage bleaching (DEpD) processes, whereas the mechanical techniques involved refining, cryo-crushing, and high-pressure homogenization. The size and morphology of the obtained fibers were characterized by environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM), and the studies showed that the isolated nanofibers from unbleached and bleached pulp had diameters between 10-90 nm, while their length was in the micrometer range. Fourier transform infrared (FTIR) spectroscopy demonstrated that the content of lignin and hemicellulose decreased in the pulping process and that lignin was almost completely removed during bleaching. Moreover, thermogravimetric analysis (TGA) indicated that both pulp types as well as the nanofibers displayed a superior thermal stability as compared to the raw kenaf. Finally, X-ray analyses showed that the chemo-mechanical treatments altered the crystallinity of the pulp and the nanofibers: the bleached pulp had a higher crystallinity than its unbleached counterpart, and the bleached nanofibers presented the highest crystallinity of all the investigated materials.

  • 306.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Khazaeian, Abolghasem
    Department of Wood and Paper Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan.
    Tahir, Paridah
    Institute of Tropical Forestry and Forest Products, University Putra Malaysia, Kuala Lumpur.
    Azry, Syeed Saiful
    Institute of Tropical Forestry and Forest Products, University Putra Malaysia, Kuala Lumpur.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Characteristics of cellulose nanofibers isolated from rubberwood and empty fruit bunches of oil palm using chemo-mechanical process2011Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 18, nr 4, s. 1085-1095Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, chemical-physical properties of nanofibers isolated from rubberwood (Hevea brasiliensis) and empty fruit bunches (EFB) of oil palm (Elaeis guineensis) were analyzed by microscopic, spectroscopic, thermal and X-ray diffraction methods. The isolation was achieved using chemo-mechanical processes. Microscopy study showed that the diameters of the nanofibers isolated from the EFB ranged from 5 to 40 nm while those of the nanofibers isolated from rubberwood had a wider range (10-90 nm). Fourier transform infrared spectroscopy study demonstrated that almost all the lignin and most of the hemicellulose were removed during the chemical treatments. X-ray diffraction analysis revealed that the crystallinity of the studied nanofibers increased after the chemo-mechanical isolation process. The results of thermogravimetric analysis showed that the nanofibers isolated from both sources had higher thermal stability than those of the bleached pulp and untreated fibers

  • 307.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Abdi, M.M.
    University Putra Malaysia.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Makinejad, M.D.
    University Putra Malaysia.
    A comparison of modified and unmodified cellulose nanofiber reinforced polylactic acid (PLA) prepared by twin screw extrusion2012Inngår i: Journal of polymers and the environment, ISSN 1566-2543, E-ISSN 1572-8919, Vol. 20, nr 4, s. 991-997Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The goal of this work was to evaluate the effect of chemical modification of cellulose nanofibers (CNF) on the properties of polylactic acid (PLA) nanocomposites. Acetylated nanofibers (ACNF), with degree of substitution 1.07, were isolated from acetylated kenaf fibers by mechanical treatments. Acetylated nanofibers showed more hydrophobic properties compared to non-acetylated ones. The results showed that both crystallinity and thermal stability of acetylated nanofibers were lower than non-acetylated ones. The nanocomposites were prepared by premixing two PLA master batches, one with a high concentration of ACNF and the second with CNF. These were diluted to final concentrations (5 wt%) during the extrusion. The morphology studies of PLA and its nanocomposites showed nanofiber aggregates in both materials. The results showed that the tensile and dynamic mechanical properties were enhanced for both acetylated and non-acetylated nanocomposites compared to the neat PLA matrix while no significant improvement was observed for the acetylated nanocomposites compared to non-acetylated ones. However, the storage modulus increased slightly for acetylated nanocomposites compared to non-acetylated ones.

  • 308. Jonoobi, Mehdi
    et al.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Natural Resources and Residues for Production of Bionanomaterials2014Inngår i: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Kapittel i bok, del av antologi (Fagfellevurdert)
  • 309.
    Jonoobi, Mehdi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Producing low-cost cellulose nanofiber from sludge as new source of raw materials2012Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 40, nr 1, s. 232-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to isolate cellulose nanofibers by ultrafine grinding, from sludge (residue from dissolving cellulose production) and cellulose (dissolving cellulose) and to characterize their properties. The mechanical fibrillation was found to be more energy efficient at low rotor speed (1440) and was estimated to be 1.7 and 1.3 kWh/kg for cellulose (CF) and sludge fibers (SF), respectively. Sludge (SNF) and cellulose (CNF) nanofibers had diameter less than 100 nm, as measured from transmission electron microscopy images. The specific surface area ranged from approximately 84 to 112 m2/g for CNF and SNF respectively. The apparent networks density increased with fibrillation, being approximately 330 and 370 for CF and SF while 907 and 986 kg/m3 for the corresponding nanosized ones. The scanning electron microscopy (SEM) study exhibited considerably smoother surfaces for the nanofiber networks compared to microsized. Fibrillation to nanosized fibers had positive impact on modulus and strength of both raw materials and the improvement was more significant for sludge, indicating more efficient fibrillation. The study showed that the isolation of nanofibers from sludge could be considered an economic, energy efficient and viable alternative to generate value-added product from cellulose sludge while minimizing the sludge disposal issues.

  • 310.
    Jonoobi, Mehdi
    et al.
    Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran.
    Oladi, Reza
    Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran.
    Davoudpour, Yalda
    School of Industrial Technology, Universiti Sains Malaysia, Penang.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dufresne, Alain
    International School of Paper, Print Media and Biomaterials (Pagora), Grenoble Institute of Technology, Université Joseph Fourier, Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS), Université Joseph Fourier.
    Hamzeh, Yahya
    Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran.
    Davoodi, Reza
    Iran Nanotechnology Initiative Council, P.O. Box 14565-344, Tehran.
    Different preparation methods and properties of nanostructured cellulose from various natural resources and residues: a review2015Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, nr 2, s. 935-969Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main goal of this article is to provide an overview of recent research in the area of cellulose nanomaterial production from different sources. Due to their abundance, renewability, high strength and stiffness, eco-friendliness and low weight, numerous studies have been reported on the isolation of cellulose nanomaterials from different cellulosic sources and their use in high-performance applications. This report covers an introduction to the definition of nanocellulose as well as the methods used for isolation of nanomaterials (including nanocrystals and nanofibers, CNCs and CNFs, respectively) from various sources. The web-like network structure (CNFs) can be extracted from natural sources using mechanical processes, which include high-pressure homogenization, grinding and refining treatments. Also, rod-like CNCs can be isolated from sources such as wood, plant fibers, agricultural and industrial bioresidues, tunicates and bacterial cellulose using an acid hydrolysis process. Following this, the article focuses on the characterization methods, material properties and structures. Encyclopedic characteristics of CNFs and CNCs obtained from different source materials and/or studies are also included. The current report is a comprehensive review of the literature regarding nanocellulose isolation and demonstrates the potential of cellulose nanomaterials for a wide range of high-tech applications.

  • 311. Jönsson, L.
    et al.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lundquist, K.
    Nyman, P. O.
    Trametes versicolor ligninase: isozyme sequence homology and substrate specificity1989Inngår i: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 247, nr 1, s. 143-146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The substrate specificity of three ligninase isozymes from the white-rot fungus Trametes versicolor has been investigated using stereochemically defined synthetic dimeric models for lignin. The isozymes have been found to attack non-phenolic β-O-4 as well as β-1 lignin model compounds. This finding confirms the classification of the isozymes from T. versicolor as ligninases. The amino-terminal residues of the three isozymes from T. versicolor have been determined using Edman degradation. Minor differences found between the sequences suggest the existence of several structural genes for ligninase in T. versicolor. Comparisons have been made with the sequences of three previously reported ligninases from Phanerochaete chrysosporium, another lignin-degrading fungus. One of the sequences from P. chrysosporium is distinctly more similar to the T. versicolor isozymes than to the other two sequences from P. chrysosporium.

  • 312.
    Jönsson, L.
    et al.
    University of Lund.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lundquist, K.
    Chalmers University of Technology.
    O., Nyman P.
    University of Lund.
    Stereospecificity in enzymic and nonenzymic oxidation of b-O-4 lignin model compounds1990Inngår i: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 276, nr 1,2, s. 45-48Artikkel i tidsskrift (Fagfellevurdert)
  • 313.
    Karim, Zoheb
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nanocellulose based affinity membranes for water purification: Processing technologies for optimal adsorption of dyes and metal ions2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The aim of current study was to fabricate high flux affinity membrane with mechanical stability, porosity and high functionality for capturing of contaminants (dyes and metal ions) from water. Cellulose nanocrystals (CNCSL) and cellulose nanofibers (CNFSL) as well as a special grade of cellulose nanocrystals (CNCBE) isolated following bioethanol pilot scale process were used for the membrane fabrication. To improve the functionality and adsorption capacity of the membranes, enzymatic phosphorylated CNCSL (PCNCSL) and in situ TEMPO functionalized CNCBE (TEMPO-CNCBE) membranes were adopted. The removal of water contaminants via adsorption on carboxyl, sulphonic and phosphoryl functional groups on nanocellulose based membranes was evaluated. Freeze-drying was used as one approach to fabricate CNCSL based hybrid membranes. In spite of high percentage removal of positively charges dyes, low water flux and mechanical stability was recorded. Very fast and effective process, viz. vacuum-filtration was further used to fabricate layered membranes with improved mechanical properties. CNFSL based support layer was coated with more functional nanomaterials (CNCSL and CNCBE) via dipping. The study showed that it was possible to tailor the specific surface area, pore sizes, water flux and wet strength of the membranes based on drying conditions (105 °C at a load of 100kN and 28 oC at ≈20N) and acetone treatment. This study was further extended to fabricate high flux bi-layered membrane having support layer of micro-sized cellulose sludge and top layer of CNCSL, CNCBE and PCNCSL within gelatin matrix for adsorption. The aim of this approach was to provide mechanical stability without decreasing the water flux significantly. In the final study, to increase the adsorption capacity of CNCBE layered membranes; in situ functionalization (TEMPO oxidation) of top layer was performed. Furthermore, CNFSL was introduced in support layer to understand the structural and functional behavior of CNFSL. All membranes were subjected to pollutants removal [dyes and Ag(I), Cu(II), Fe(II)/Fe(III) metal ions]. Remarkable increase in adsorption capacity towards metal ions was recorded after modification of nanocellulose (phosphorylation and in situ functionalization). The outstanding performance of nanocellulose reveals the possibility of next generation affinity membranes for water purification.

  • 314.
    Karim, Zoheb
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Processing and characterization of membranes based on cellulose nanocrystals for water purification: Nanocellulose as functional entity2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Membrane technology is being extensively used in water purification as an energy efficient and low cost process. Nanostructured (NSM) and nanoenabled (NEM) membranes are favored in this context as nanoscaled entities are expected to provide high surface area, high mechanical properties and versatile surface chemistry as well as provide better control on the pore size and distribution, flux and selectivity of the membrane. Biobased nanoparticles as nanocrystals are expected to have a significant advantage in this context. Thus, the main aim of this work was to explore the use of cellulose nanocrystals as functional entities for the fabrication of nanoenabled composite membranes and apply these fabricated membranes for the removal of dyes and metal ions from polluted water. The first study deals with the isolation of cellulose nanocrystals (CNCBE) from wood using the bioethanol pilot scale setup. Cellulose was prepared from wood by diluted acid treatment in the bioethanol plant followed by dewaxing and bleaching. The cellulose was converted into cellulose nanocrystals by mechanical grinding using lab scale homogenizer. The isolated nanoparticles had a diameter of 5-15 nm and formed a thick gel at 2 wt%. X-ray photoelectron spectroscopy illustrated the presence of O=C-O surface functional groups, directly related to the negative zeta-potential values. Fabricated films of CNCBE denoted good mechanical properties, optical properties and cytocompatibility. Thus, a new isolation route that can be followed to produce nanocrystals in large quantities (600 g/ day) has been developed. In a second study, fully biobased nanocomposite membranes of cellulose nanocrystals and chitosan have been fabricated by freeze-drying and crosslinking with gluteraldehyde in vapor phase. The chitosan bound the CNCSL in a stable and nanoporous membrane network with thickness of 250-270 μm. Homogenous dispersion of CNCSL within chitosan matrix was reported based on scanning electron microscopy (SEM). The Brunauer Emmett and Teller (BET) studies showed a decrease in surface area (3.1 to 2.9 m2/g) and average pore size (17 to 13 nm) after crosslinking. The mechanical performance of composite membranes was low, being 0.98 ± 0.4 and 1.1 ± 0.3 MPa of tensile strength for uncross-linked and cross-linked membranes, respectively. In spite of low water flux (64 L m−2 h−1), the composite membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, from a model wastewater after a contact time of 24 h. In the third study layered membranes containing a highly porous support layer and a dense functional layer has been fabricated following a filtration and hot pressing method. Microsized cellulose fibers from sludge bioresidues was used as the support layer to provide mechanical stability and allow water flow without any hindrance. A nanocomposite system of nanocrystals (CNCSL, CNCBE and PCNCSL) with gelatin as matrix was used as the functional layer. Bubble point measurement confirmed the membrane pore sizes (5-6 m), in microfiltration range, which resulted in high water permeability < 4000 Lh-1m-2 at 1.5 bars. Efficient removal of Ag+, Cu2+ and Fe3+ from industrial wastewater was achieved using these membranes. The removal of metal ions was expected to be driven by the electrostatic attraction between negatively charged nanocellulose and the positively charged metal ions. The work has demonstrated that highly efficient water treatment membranes can be fabricated from nanocellulose via tailoring their ability to interact and selectively adsorb heavy metal ions and dyes.

  • 315.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Afrin, Sadaf
    Department of Chemistry, Faculty of Sciences , Aligarh Muslim University .
    Hussain, Qayyum
    Department of Biochemistry, Faculty of Life Sciences , Aligarh Muslim University .
    Danish, Rehan
    Infinity Vacuum Technology , Geomdan Techpart Geomdangondan-Ro 26, Buk-Gu , Daegu .
    Necessity of enzymatic hydrolysis for production and functionalization of nanocelluloses2017Inngår i: Critical reviews in biotechnology, ISSN 0738-8551, E-ISSN 1549-7801, Vol. 37, nr 3, s. 355-370Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocellulose (NC) from cellulosic biomass has recently gained attention owing to their biodegradable nature, low density, high mechanical properties, economic value and renewability. They still suffer, however, some drawbacks. The challenges are the exploration of raw materials, scaling, recovery of chemicals utilized for the production or functionalization and most important is toxic behavior that hinders them from implementing in medical/pharmaceutical field. This review emphasizes the structural behavior of cellulosic biomass and biological barriers for enzyme interactions, which are pertinent to understand the enzymatic hydrolysis of cellulose for the production of NCs. Additionally, the enzymatic catalysis for the modification of solid and NC is discussed. The utility of various classes of enzymes for introducing desired functional groups on the surface of NC has been further examined. Thereafter, a green mechanistic approach is applied for understanding at molecular level

  • 316.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Claudpierre, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nanocellulose based functional membranes for water cleaning: Tailoring of mechanical properties, porosity and metal ion capture2016Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 514, s. 418-428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multi-layered nanocellulose membranes were prepared using vacuum-filtration of cellulose nanofibers (CNF) suspensions followed by dip coating with cellulose nanocrystals having sulphate (CNCSL) or carboxyl surface groups (CNCBE). It was possible to tailor the specific surface area, pore structure, water flux and wet strength of the membranes based on drying conditions and acetone treatment. CNF coated with CNCBE showed the highest a tensile strength (95 MPa), which decreased in wet conditions (≈3.7 MPa) and with acetone (2.7 MPa) treatment. The water dried membranes showed pore sizes in nanofiltration range (74 Å) from liquid nitrogen adsorption/desorption data and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194Å) with a concomitant increase (7000%) of the BET surface area. The water flux, also increased from zero to 25 Lm-2h-1 at a pressure differential of 0.45 MPa, for acetone treated ones. The membranes irrespective of the surface functionality showed exceptional capability (≈100%) to remove Ag+, Cu2+ and Fe3+ ions from mirror industry effluents. Surface adsorption followed by microprecipitation was considered as the possible mechanism of ion removal, which opens up a new generation of ultrafiltration membranes with high selectivity towards ions and low-pressure demands.

  • 317.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Chitosan based nanocomposite membranes with cellulose nanowhisker as nanoadditive2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biobased nanocomposite membranes were prepared using chitosan as te matrix and cellulose nano whisker as the reinforcing phase. Cellulosee production. Atomic force microscopy of the nanowhiskers showed diameters of 10 -20nm and lengths of 250 - 350nm. Nanocomposites were prepared in 1:1, 1:2 and 1:3 ratios to investigate the effect of nanoadditive concentration on the membrane properties. The nanocomposites were prepared by solution mixing followed by freeze-drying, to obtain porous structures with high degree of internal surface area. These nanocomposites were further treated with ammonia vapours to prepare the crosslinked nanocomposites and thereby stabilize it towards moisture and pH variations. The morphology, surface area, crystallinity, porosity, and mechanical properties of prepared membranes were studied. The effect of the nanocomposite composition, crosslinking and the pore size distribution on the water transport through the membranes was also evaluated.

  • 318.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hakalahti, Minna
    VTT Technical Research Centre of Finland.
    Tammelin, Tekla
    VTT Technical Research Centre of Finland.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University.
    In situ TEMPO surface functionalization of nanocellulose membranes for enhanced adsorption of metal ions from aqueous medium2017Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, nr 9, s. 5232-5241Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current work demonstrates an innovative approach to develop nanocellulose based membranes with high water permeability, mechanical stability and high functionality via (1) tailoring the composition of the support layer of sludge microfibers/cellulose nanofibers (CNFSL) and (2) in situ TEMPO functionalization of the thin functional layer of cellulose nanocrystals (CNCBE) to enhance the metal ion adsorption capacity. SEM studies showed a porous network structure of the cellulose support layer and a denser functional layer with CNCBE embedded within gelatin matrix. AFM studies indicated the presence of a nanoscaled coating and increased roughness of membranes surface after TEMPO modification whereas FT-IR and conductometric titration confirmed the introduction of carboxyl groups upon TEMPO oxidation. The contact angle measurement results showed improved hydrophilic nature of membranes after in situ TEMPO functionalization. High networking potential of CNFSL made the membrane support layer tighter with a concomitant decrease in the average pore size from 6.5 to 2.0 μm. The coating with CNCBE further decreased the average pore size to 0.78 and 0.58 μm for S/CNCBE and S–CNFSL/CNCBE, respectively. In parallel, a drastic decrease in water flux (8000 to 90 L MPa−1 h−1 m−2) after coating with CNCBE was recorded but interestingly in situ functionalization of top CNCBE layer did not affect water flux significantly. The increase in adsorption capacity of ≈1.3 and ≈1.2 fold was achieved for Cu(II) and Fe(II)/Fe(III), respectively after in situ TEMPO functionalization of membranes. Biodegradation study confirmed the stability of layered membranes in model wastewater and a complete degradation of membranes was recorded after 15 days in soil.

  • 319.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Khan, Mohd Jahir
    School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi.
    Maskat, Mohamad Yusof
    School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi.
    Adnan, Rohana
    School of Chemical Sciences, Universiti Sains Malaysia, Minden Penang.
    Immobilization of horseradish peroxidase on β-cyclodextrin-capped silver nanoparticles: Its future aspects in biosensor application2016Inngår i: Preparative Biochemistry & Biotechnology, ISSN 1082-6068, E-ISSN 1532-2297, Vol. 46, nr 4, s. 321-327Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study aimed to work out a simple and high-yield procedure for the immobilization of horseradish peroxidase on silver nanoparticle. Ultraviolet–visible (UV-vis) and Fourier-transform infrared spectroscopy and transmission electron microscopy were used to characterize silver nanoparticles. Horseradish peroxidase was immobilized on β-cyclodextrin-capped silver nanoparticles via glutaraldehyde cross-linking. Single-cell gel electrophoresis (Comet assay) was also performed to confirm the genotoxicity of silver nanoparticles. To decrease toxicity, silver nanoparticles were capped with β-cyclodextrin. A comparative stability study of soluble and immobilized enzyme preparations was investigated against pH, temperature, and chaotropic agent, urea. The results showed that the cross-linked peroxidase was significantly more stable as compared to the soluble counterpart. The immobilized enzyme exhibited stable enzyme activities after repeated uses.

  • 320.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nanoporous membranes with cellulose nanocrystals as functional entity in chitosan: removal of dyes from water2014Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 112, s. 668-676Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fully biobased composite membranes for water purification were fabricated with cellulose nanocrystals (CNCs) as functional entities in chitosan matrix via freeze-drying process followed by compacting. The chitosan (10 wt%) bound the CNCs in a stable and nanoporous membrane structure with thickness of 250-270 μm, which was further stabilized by cross-linking with gluteraldehyde vapors. Scanning electron microscopy (SEM) studies revealed well-individualized CNCs embedded in a matrix of chitosan. Brunauer, Emmett and Teller (BET) measurements showed that the membranes were nanoporous with pores in the range of 13-10 nm. In spite of the low water flux (64 L m-2 h-1), the membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, after a contact time of 24 h. The removal of dyes was expected to be driven by the electrostatic attraction between negatively charged CNCs and the positively charged dyes.

  • 321.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kokol, Vanja
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Wei, Jiang
    Alfa Laval Nakskov A/S, Business Center Membranes, Stavangervej 10, DK-4900, Nakskov, Denmark.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    High-flux affinity membranes based on cellulose nanocomposites for removal of heavy metal ions from industrial effluents2016Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 25, s. 20644-20653Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fully biobased affinity membrane processing and its application in the removal of heavy metal ions from mirror industry effluents were successfully demonstrated; indicating the potential use of these membranes in point-of-use or point-of-entry water cleaning products that are cheap, environmentally friendly and efficient. Layered cellulose nanocomposite membranes were fabricated using cellulose microfiber sludge as a support layer and cellulose nanocrystals (CNCSL, CNCBE or PCNCSL) in a gelatin matrix as the functional layer. Scanning electron microscopy (SEM) studies revealed the bi-layered morphology of the membrane and well-individualized nanocelluloses in the functional layer. Bubble point measurements confirmed the membrane pore structure in the microfiltration range (5.0-6.1 μm), which provided very high water permeability (900-4000 L h-1 m-2) at <1.5 bars. A tensile strength of 16 MPa in dry conditions and a wet strength of 0.2 MPa, was considered sufficient for use of these membranes in spiral wound modules. Mirror industry effluent laden with metal ions (Ag+ and Cu2+/Fe3+/Fe2+) when treated with cellulose nanocomposite membranes, showed high ion removal capacity, being 100% for PCNCSL followed by CNCBE than CNCSL. The removal of metal ions was expected to be driven by interactions between negatively charged nanocellulose and the positively charged metal ions.

  • 322.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cellulose nanocrystals based nanocompositemembranes for water purification: Process-Property correlation2015Konferansepaper (Annet vitenskapelig)
  • 323.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Fully biobased nanocomposite membranes: removal of heavy metals from polluted water2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biobased nanoparticles viz cellulose nanocrystals (CNCs) and cellulose nanofiber (CNFs) isolated by mechanical process (grinding) were used to fabricate of fully biobased nanocomposite membranes. Biobased nanofibers were used as support layer via a very simple process of vacuum filtration was used for the fabrication of CNF support layer. In order to coat CNCs or CNCbio on the two sides to CNF layer, the membrane was dipped in a solution of cellulose nanocrystals. Scanning electron microscopy (SEM) confirmed the infusion of functional layer within supportive layer. Tensile strength was measured in dry as well as in wet conditions, illustrated mechanical performances compareble to commercially available membranes. To increase the flux, membranes were treated with acetone for 24 and 72 h. The drastic increase in the flux for acetone treated membranes confirmed the discontinuities of hydrogen . The membranes succefully removed two metal ions Ag+ and As3- from real wastewater, from mirror making and mining industries respectively, within Europe. Complete removal of Ag+ was reported after 24 h of incubation. The study concludes that, the developed membranes having good mechanical stability in wet conditions, high water flux and adsorption efficiency are potential candidates for heavy metal ion remediation of industrial effluents.

  • 324. Karjalainen, P.
    et al.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Steen, P.
    Comparison of the thermo-mechanical treatments of some steels conducted at a pilot plant and by physical simulation1992Inngår i: Proceedings of the International Symposium on Physical Simulation: Delft 1992 ; ... conference was held on April 22 - 24 in Delft, The Netherlands, Poestenkill, NY: DSI, Duffers Scientific , 1992, s. 43-48Konferansepaper (Fagfellevurdert)
  • 325.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Dagbro, Ola
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Granlund, Kurt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Soluble degradation products in thermally modified wood2014Inngår i: Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts / [ed] Mojgan Vaziri, Dick Sandberg, Skellefteå: Luleå tekniska universitet, 2014, s. 16-17Konferansepaper (Fagfellevurdert)
  • 326.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Ikeda, Tsutomu
    Wood Chemistry Laboratory.
    Kishimoto, Takao
    Wood Chemistry Laboratory.
    Magara, Kengo
    Wood Chemistry Laboratory.
    Matsumoto, Yuji
    Wood Chemistry Laboratory.
    Hosoya, Shuji
    Wood Chemistry Laboratory.
    Isolation of lignin-carbohydrate bonds in wood: model experiments and preliminary application to pine wood2004Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 50, nr 2, s. 141-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel method for analysis of benzylic ether type lignin-carbohydrate bonds has been developed by using model compounds. Four diastereomers of model compound 3-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-3-(methyl -d-glucopyranoside-6-O-yl)-1-propanol (GGMGP), were ozonized in acetic acid/water/methanol 16:3:1 for 1h at 0°C. The product from ozonation of each diastereomer was saponified and the corresponding -etherified tetronic acid (TAMGP) was isolated using ion exchange chromatography. Minor amounts of methyl -d-glucopyranoside (MGP) and small amounts of a gluconic acid etherified with tetronic acid (TAGLCA), tetronic acid, gluconic acid, and glyceric acid were detected in the product mixture of ozonated benzylic ether type model compounds. The results suggest that a benzyl ether bond between lignin and carbohydrate is rather stable during the ozone treatment. Acid treatments with sulfuric acid or trifluoroacetic acid of the derived TAMGP led to cleavage of the glucosidic bond but only a small amount of products (tetronic acid and glucose) resulting from cleavage of the -ether bond were formed. The successful chemical treatments were used for studies of benzylic ether bonds in Japanese red pine. The results suggest the presence of benzylic ether bonds to polysaccharides in the wood.

  • 327.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Ikeda, Tsutomu
    Forestry and Forest Products Research Institute.
    Kishimoto, Takao
    Forestry and Forest Products Research Institute.
    Magara, Kengo
    Forestry and Forest Products Research Institute.
    Matsumoto, Yuji
    Forestry and Forest Products Research Institute.
    Hosoya, Shuji
    Forestry and Forest Products Research Institute.
    Ozonation of a lignin-carbohydrate complex model compound of the benzyl ether type2000Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 46, nr 3, s. 263-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Evidence for the presence of lignin-carbohydrate bonds of the benzylic ether type in wood and pulps may be obtained by use of ozonation treatment to selectively degrade the lignin. It was found that the benzyl ether bond in 3-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxy-phenoxy)-3-(methyl--d-glucopyranosid-6-O-yl)-1-propanol was rather stable during ozonation in acetic acid-water-methanol 1631 at 0°C. The corresponding acid, 3,4-dihydroxy-2-(methyl--d-glucopyranosid-6-O-yl)-butanoic acid, was found to be the major reaction product. The use of ozonation followed by acid hydrolysis in connection with studies of lignincarbohydrate linkages is briefly discussed.

  • 328.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Ikeda, Tsutomu
    Magara, Kengo
    Hosoya, Shuji
    Novel method for isolation of a lignin-carbohydrate bond2001Inngår i: 11th ISWPC: Symposium on Wood and Pulping Chemistry; Nice, France, June 11 to 14, 2001, Nice, 2001Konferansepaper (Fagfellevurdert)
  • 329.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lundquist, Knut
    Acid reactions of hydrobenzoins: effect of catalyst and reaction medium on product composition1992Inngår i: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 46, s. 283-289Artikkel i tidsskrift (Fagfellevurdert)
  • 330.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lundquist, Knut
    Chalmers University of Technology.
    Stomberg, Rolf
    Chalmers University of Technology.
    Preparation and crystal structure of (+/-)-1,2-Bis(3,4-dimethoxyphenyl)-1,2-ethanediol1993Inngår i: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 47, s. 728-733Artikkel i tidsskrift (Fagfellevurdert)
  • 331.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lundquist, Knut
    Stomberg, Rolf
    Studies on hydrobenzoins: preparation, crystal structure and stability of borate complexes1990Inngår i: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 44, s. 617-624Artikkel i tidsskrift (Fagfellevurdert)
  • 332.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Colour stabilization of heat modified Norway spruce exposed to out-door conditions2010Inngår i: Proceedings, 11th International IUFRO Wood Drying Conference: [... in Skellefteå, Sweden, January 18 - 22, 2010 ... the theme of the conference was "Recent Advances in the Field of Wood Drying"] / [ed] Tom Morén; Lena Antti; Margot Sehlstedt-Persson, Luleå: Luleå tekniska universitet, 2010, s. 265-268Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wood boards from Norway spruce (300 mmx125mmx10mm) were heat modified in a pilot chamber corresponding to Thermowood-D quality. The surface of boards was sprayed with diluted solutions of ferrous sulphate alone or in combination with subsequent spraying of a 30% solution of hydrogen peroxide. The boards were exposed to outdoor conditions during summer 2009 (45o facing south). Colour coordinates were measured using a colorimeter.Only small changes in colour of boards were observed directly after the surface treatments. Lightness increased for boards with no surface treatments during out-door exposure (seven weeks). Increase in lightness was delayed when ferrous sulphate was applied to the board. Lightness was essentially unchanged during the out-door exposure period when ferrous sulphate and hydrogen peroxide was used to modify the wood surface (at low hydrogen peroxide charge a small increase of lightness was, however, observed). Chroma decreased for boards with surface treatments but levelled out after a couple of weeks. On the other hand a decrease in chroma of boards with no surface treatments started after about four weeks exposure. Hue increased for all the boards until the fourth week. After that hue of untreated boards and boards treated with both ferrous sulphate and hydrogen peroxide continue to increase.

  • 333.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Pettersson, B.
    Westermark, Ulla
    Linkages between residual lignin and carbohydrates in bisulphite (magnefite) pulps2001Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, nr 9, s. 310-316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The presence of bonds between residual lignin and carbohydrates in bisulphite pulps from hardwoods and softwoods was studied. Results showed that a fraction of the residual lignin was bonded to cellulose in bisulphite pulps of softwood. The treatment with xylanase indicated the existence of alkali-stable lignin-xylan bonds in softwood bisulphite pulps.

  • 334.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Pettersson, B.
    Westermark, Ulla
    The use of cellulases and hemicellulases to study lignin-cellulose as well as lignin-hemicellulose bonds in kraft pulps2001Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, nr 6, s. 196-201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The combination of carbohydrate-degrading enzymes and size-exclusion chromatography (SEC) has been used to analyze the existence of covalent bonds between lignin and cellulose and/or hemicelluloses in pulps. Cellulases and xylanase were used for degradation of cellulose and xylan, respectively. Analysis of the molecular weight profiles of lignin and carbohydrates before and after enzymic hydrolysis were performed by dissolution of the pulps in LiCl/dimethylacetamide (DMAC). The results indicate that a considerable part of the residual lignin in unbleached pine kraft pulp is bond to cellulose. Bonding of lignin to xylan in the pine kraft pulp could also be detected. Analysis of birch kraft pulp shows that most of the residu lignin in birch kraft pulps is covalently linked to xylan. The combination of carbohydrate-degrading enzymes and SEC in LiCl/DMAC seems to be an excellent way of characterizing bonds between lignin and carbohydrates in chemical pulps.

  • 335.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Yang, Qian
    Heat treatments of high temperature dried norway spruce boards: Saccharides and furfurals in sapwood surfaces2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 2, s. 2284-2299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbohydrates that migrate to wood surfaces in sapwood during drying might influence properties such as mould susceptibility and colour. Sugars on the surface of Norway spruce boards during various heat treatments were studied. Samples (350mm×125mm×25mm) were double-stacked, facing sapwood-side outwards, and dried at 110°C to a target moisture content (MC) of 40%. Dried sub-samples (80 mm × 125 mm × 25 mm) were stacked in a similar way and further heated at 110°C and at 130°C for 12, 24, and 36 hours, respectively. Glucose, fructose, and sucrose as well as 5-hydroxymethylfurfural (HMF) and furfural in the sapwood surface layer of treated wood were analysed using HPLC (RI- and UV-detectors). Carbohydrates degraded to a lower extent at 110°C than at 130°C. Furfural and to a larger extent HMF increased with treatment period and temperature. Heat treatment led to a decrease in lightness and hue of the sapwood surface of sub-samples, while chroma increased somewhat. Furthermore, considerably faster degradation (within a few minutes) of the carbohydrates on the surface of the dried spruce boards was observed when single sub-samples were conductively hot pressed at 200°C. Treatment period and initial MC influenced the presence of the carbohydrates in wood surface as well as colour change (ΔE ab) of the hot pressed sub-samples.

  • 336.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sidorova, Ekaterina
    SP Technical Research Institute of Sweden.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Influence of heat transferring media on durability of thermally modified wood2011Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 6, nr 1, s. 356-372Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies on the durability and dimensional stability of a series of hardwoods and softwoods after thermal modification in vegetable oils and in steam atmospheres have been performed. Mass loss after exposure to Coniophora puteana (BAM Ebw. 15) for 16 weeks was very low for European birch, European aspen, Norway spruce, and Scots pine thermally modified in a linseed oil product with preservative (for 1 hour at 200 degrees C). Fairly low mass losses were obtained for wood thermally modified in linseed-, tung-and rapeseed oil, and losses were related to the wood species. Low mass loss during rot test was also found for Norway spruce and Scots pine modified in saturated steam at 180 degrees C. Water absorption of pine and aspen was reduced by the thermal treatments and the extent of reduction was dependent on wood species and thermal modification method. Thermally modified aspen was stable during cycling climate tests, whereas pine showed considerable cracking when modified under superheated steam conditions (Thermo D). At lower modification temperature (180 degrees C) an increase in mass after modification in rapeseed oil of spruce, aspen and sapwood as well as heartwood of pine was observed, whereas at high temperature (240 degrees C) a mass loss could be found. Oil absorption in room tempered oil after thermal modification in oil was high for the more permeable aspen and pine (sapwood).

  • 337.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Torniainen, Petteri
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Dagbro, Ola
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Granlund, Kurt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Morén, Tom
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Presence of water-soluble compounds in thermally modified wood: carbohydrates and furfurals2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 3, s. 3679-3689Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With thermal modification, changes in properties of wood, such as the presence of VOC and water-soluble carbohydrates, may occur. Thermal modifications under saturated steam conditions (160°C or 170°C) and superheated steam conditions (170, 185, and 212°C) were investigated by analysing the presence of water-soluble 5-(hydroxymethyl)furfural (HMF), furfural, and carbohydrates in heat-treated wood. The influence of thermal modifications on Scots pine, Norway spruce, and silver birch was also studied. Furfurals were analysed using HPLC at 280 nm, while monosaccharides and water-soluble carbohydrates were determined by GC-FID as their acetylated alditiols and, after methanolysis, as their trimethylsilylated methyl-glycosides, respectively. The amount of furfurals was larger in boards thermally modified under saturated steam conditions than those treated under superheated steam conditions. Generally, more of HMF than furfural was found in the thermally modified boards. In process water, in which saturated steam conditions had been used, furfural and only traces of HMF were found. Higher content of water-soluble carbohydrates was found in boards treated in saturated steam rather than in superheated steam. After modification in saturated steam, substantial parts of the water-soluble carbohydrates were due to monosaccharides, but only traces of monosaccharides were found in boards treated under superheated steam conditions.

  • 338.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Westermark, Ulla
    Auto-adhesive bonding by oxidative treatment of wood2003Inngår i: Proceedings of the 12th International Symposium on Wood and Pulping Chemistry: University of Wisconsin-Madison, Department of Forest Ecology and Management, June 9 - 12, 2003, Madison, Wisconsin, USA, Madison, Wis, 2003, s. 365-368Konferansepaper (Fagfellevurdert)
  • 339.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Westermark, Ulla
    Evidence for chemical bonds between lignin and cellulose in kraft pulps1996Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 22, nr 10, s. J397-401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The cellulose solvent system LiCl-dimethylacetamide has been used to dissolve kraft pulps prepared from pine and birch. The dissolved polymers were analyzed using size-exclusion chromatography combined with both RI- and UV-detection systems in order to monitor simultaneously the major wood polymers (cellulose, hemicellulose and lignin). Kraft pulps from birch were completely soluble in the solvent system and the pine kraft pulp about 80% soluble. Analyses of the kraft pulps strongly suggest that a considerable amount of the residual lignin is chemically linked to the high molecular weight cellulose in pine but not in birch. The presence of stable lignin-cellulose bonds will reduce the possibility of achieving a low kappa number by cooking. For comparison, sulphite and bisulphite pulps were also examined. Both pulps were soluble in the solvent system and analyses indicated that lignin-cellulose bonds also exist in these pulps although to a significantly lesser extent than in the pine kraft pulp

  • 340.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Westermark, Ulla
    Resin-free particleboard by oxidation of wood2002Inngår i: 6th Pacific Rim Bio-Based Composites Symposium & Workshop on the Chemical Modification of Cellulosics: November 10th to 13th 2002, Portland, Oregon ; proceedings / [ed] P. E. Humphrey, Corvallis, Or: Wood science and engineering department , 2002Konferansepaper (Fagfellevurdert)
  • 341.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Westermark, Ulla
    The significance of glucomannan for the condensation of cellulose and lignin under kraft pulping conditions1997Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 12, nr 2, s. 90-Artikkel i tidsskrift (Fagfellevurdert)
  • 342.
    Karlsson, Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Westermark, Ulla
    Backlund, Ulrika
    Metso, Sundsvall.
    Halvarsson, Sören
    Mittuniversitetet.
    Environmentally friendly process for high density fibreboards2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Urea-formaldehyde (UF) resin is a common binder in many fibre- and particleboards today. However, formaldehyde is a fairly reactive compound with many negative affects on health and environment. This paper describes a process to make thin high density fibreboards without use of conventional resin such as UF. Initially we found that wood particles such as ones used in particle board had, when activated with hydrogen peroxide and iron catalyst, self-bonding capability when hot-pressed into boards. Low swelling board, although at somewhat higher density than conventional glued ones, could be formed by pressing activated wood particles at 170 oC in a laboratory press. We found that the activation technique was applicable to dry or semi-dry board processes and was considered to be well suited for fibreboards from refined wood fibers especially as their specific (contact) area is high. Activated wood fibres were produced at Metso Panelboards Pilot-refiner in Sundsvall and mats were also formed and pressed into boards 50x60 cm2 at fairly conventional pressing conditions. At a hydrogen peroxide charge of 4% boards made from birch fibres with good mechanical properties (in terms of bending strength and internal bonding) were produced. Thickness swelling in water was low (TS24h., 15-20%). At lower hydrogen peroxide charges (<2%) the swelling was higher. Development of the process to also include other wood species than birch is in our interest. Furthermore, properties of the boards were strongly dependent on the moisture content of fibres; at low moisture content (MC<8%) thickness swelling increased. We see a high potential in the process as the glue-free technique is estimated to reduce production cost of boards as well as give environmental advantages.

  • 343.
    Kekäläinen, Kaarina
    et al.
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Suopajärvi, Terhi
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Mathew, Aji P.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Laitinen, Ossi
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Niinimäki, Jouko
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Effect of peroxide treatment on energy consumption of refining and quality2010Inngår i: International Paperworld, ISSN 1615-1720, Vol. 9, s. 12-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of alkaline hydrogen peroxide treatment on microfibrillar cellulose (MFC) production in an inline homogenizer (ZRI) was reported. Never-dried bleached softwood Kraft pulp (BSK) from the Stora Enso Oulu mill in Finland and never-dried dissolving cellulose (DC) from the Domsjö Fabriker AB Örnsköldsvik mill in Sweden were used. The analyses of the celluloses were carried out in three phases that included for the early refining stage, the later stage of refining and for the final product. The final refining products and the commercial MFC were visualized by FESEM (Zeiss Ultra Plus) and by AFM (VEECO multimode scanning probe microscope with a Nanoscope V controller). The results showed that the particle size of the dissolving cellulose decreased more in the early refining stage, whereas the bleached Kraft pulp was refined more in the later stage of refining. Alkaline peroxide treatment had a significant effect on the fiber width development compared to the development of alkali-treated celluloses

  • 344.
    Keskisaari, Anna
    et al.
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Butylina, Svetlana
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Kärki, Timo
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Use of construction and demolition wastes as mineral fillers in hybrid wood-polymer composites2016Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 133, nr 19, artikkel-id 43412Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The recycling of construction materials has been the subject of much research in past years. In this study, the use of construction and demolition wastes (CDWs) as mineral fillers in hybrid wood-polymer composites was studied. Two types of waste materials were used as fillers in the composites: (1) a mixture consisting of waste mineral wool (MW) and plasterboard (PB) and (2) mixed CDWs. The performance of the composites was evaluated from their mechanical properties and water-absorption behavior. We found in the study that the addition of mineral fillers decreased the flexural strength and modulus values of the wood-polypropylene (PP) composites. On the other hand, the exchange of part of the wood with a mineral filler resulted in an increase in the impact strength of the composite. The composite manufactured with the combination of MW and PB had the lowest water absorption. The decrease in wood loading resulted in improved dimensional stability in the hybrid wood-mineral filler-PP composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43412.

  • 345.
    Khosravi, Fatemeh
    et al.
    Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran.
    Khorasani, Saied Nouri
    Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran.
    Ghomi, Erfan Rezvani
    Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran.
    Kichi, Mohsen Karimi
    Department of Material Engineering, Isfahan University of Technology, Isfahan, Iran.
    Zilouei, Hamid
    Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran.
    Farhadian, Mousa
    Department of Material Engineering, Isfahan University of Technology, Isfahan, Iran.
    Neisiany, Rasoul Esmaeely
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran.
    A bilayer GO/nanofibrous biocomposite coating to enhance 316L stainless steel corrosion performance2019Inngår i: Materials Research Express, ISSN 2053-1591, Vol. 6, nr 8, artikkel-id 086470Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A bilayer coating has been synthesized to be coated on the 316L stainless steel (SS) for bone implant application. The first layer consisted of graphene oxide (GO) which was coated via the electrophoretic deposition method. The second layer including Poly (ε-caprolactone) (PCL)/Gelatin-forsterite nanofibers was electrospun on the first layer. The morphology of the bare 316L SS, GO-coated, electrospun nanofibers, and nanofibers-coated samples were investigated using scanning electron microscopy (SEM). The electrospun nanofibers were also characterized by Fourier transform infrared spectroscopy (FTIR) and confirmed the presence of PCL, gelatin, and forsterite in the nanocomposite coating. Furthermore, the morphological investigation of the nanofibers revealed that 80:20 weight of PCL to gelatin did not show any beads, making them for coating on the GO coatings. In addition, the corrosion behavior of the coated samples was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The samples coated with GO and GO/PCL-gelatin-forsterite 1% showed the best corrosion resistance in comparison with other samples. Consequently, the prepared bilayer biocomposite coating including 1 wt% forsterite nanoparticles can be a promising candidate for orthopedic implants.

  • 346.
    Kifetew, Girma
    et al.
    Kungliga tekniska högskolan, KTH.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Wiklund, Martin
    Kungliga tekniska högskolan, KTH.
    Tangential and radial deformation field measurements on wood during drying1997Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 31, nr 1, s. 35-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a previous study, the deformation field measurement method on wood during drying was described. This paper discusses the deformation field measurement results during drying to 8.2% moisture content on the radial and tangential surfaces. It also attempts to explain the observations by an approximate expression based onearlywood-latewood interaction theory. The deformation on the radial surface varied between -0.7% and 7.5%. The actual measurements on the radial surfaces support previous work. Deformation measurements on the tangential surfaces were between -0.5% and 9.0%. Although the investigations were carried out on gross wood specimens, the results provide an insight into the extent to which local density variation within the early- and latewood layers may influence the magnitude of surface deformation.

  • 347.
    Kishimoto, Takao
    et al.
    Forestry and Forest Products Research Institute.
    Ikeda, Tsutomu
    Wood Chemistry Laboratory, Forestry and Forest Products Research Institute, 305-8687 Ibaraki.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Magara, Kendo
    Wood Chemistry Laboratory, Forestry and Forest Products Research Institute, 305-8687 Ibaraki.
    Hosoya, Shuji
    Wood Chemistry Laboratory, Forestry and Forest Products Research Institute, 305-8687 Ibaraki.
    Reactivity of secondary hydroxyl groups in methyl β-D-xylopyranoside toward a β-O-4-type quinone methide2002Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 48, nr 1, s. 32-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Methyl β-D-xylopyranoside was allowed to react with β-O-4-type quinone methide without a catalyst to elucidate the reactivities of secondary hydroxyl groups at the C2, C3, and C4 positions. Benzyl ether-type lignin-carbohydrate complex (LCC) compounds linked at the C2 and C4 positions were predominant, at a ratio of 2:3. However, the reactivity of the hydroxyl group at the C3 position was quite low. These results strongly suggest that the reactivity of the C2 hydroxyl group in xylan toward quinone methide intermediate is higher than that of the C3 hydroxyl group during biosynthesis of LCCs

  • 348.
    Koivuranta, Elisa
    et al.
    Fibre and Particle Engineering Research Unit, Faculty of Technology, University of Oulu.
    Hietala, Maiju
    Fibre and Particle Engineering Research Unit, Faculty of Technology, University of Oulu.
    Ämmälä, Ari
    Fibre and Particle Engineering Research Unit, Faculty of Technology, University of Oulu.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Illikainen, Mirja
    Fibre and Particle Engineering Research Unit, Faculty of Technology, University of Oulu .
    Improved durability of lignocellulose-polypropylene composites manufactured using twin-screw extrusion2017Inngår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 101, s. 265-272Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study was to investigate the use of peat as a potential lignocellulose source in composites manufactured by twin-screw extrusion. The effects of peat decomposition rate and particle size on the mechanical properties and moisture resistance of peat-polypropylene (PP) composites under cyclic conditions were evaluated. The properties of the peat-PP composites were compared to commercial lignocellulosic fibre products, namely wood-plastic composite (WPC), medium density fibreboard (MDF) and hardboard (HB). The results show that prior cyclic freeze-thaw testing peat-PP composites had properties equal to commercial WPC, but their mechanical permanence was better after freeze-thaw conditioning. When moderately decomposed, smaller particle–size peat was used, peat-PP composites had better dimensional stability, though particle size did not affect as much as the decomposition degree. Thus, the chemical structure of peat has a greater influence on composite durability, as better water and weather resistance are achieved with peat that is more decomposed.

  • 349.
    Kokol, Vanja
    et al.
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Bozic, Mojca
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Vogrinčič, Robert
    Faculty of Mechanical Engineering, Institute for Engineering Materials and Design, University of Maribor.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Characterization and properties of homo- and heterogenously phosphorylated nanocellulose2015Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 125, s. 301-313Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nano-sized cellulose ester derivatives having phosphoryl side groups were synthesised by phosphorylation of nanofibrilated cellulose (NFC) and nanocrystaline cellulose (NCC), using different heterogeneous (in water) and homogeneous (in molten urea) processes with phosphoric acid as phosphoryl donor. The phosphorylation mechanism, efficacy, stability, as well as its influence on the NC crystallinity and thermal properties, were evaluated using ATR-FTIR and 13C-NMR spectroscopies, potentiometric titration, capillary electrophoresis, X-ray diffraction, colorimetry, thermogravimmetry and SEM. Phosphorylation under both processes created dibasic phosphate and monobasic tautomeric phosphite groups at C6 and C3 positioned hydroxyls of cellulose, yielded 60-fold (∼1173 mmol/kg) and 2-fold (∼1038 mmol/kg) higher surface charge density for p-NFC and p-NCC, respectively, under homogenous conditions. None of the phosphorylations affected neither the NC crystallinity degree nor the structure, and noticeably preventing the derivatives from weight loss during the pyrolysis process. The p-NC showed high hydrolytic stability to water at all pH mediums. Reusing of the treatment bath was examined after the heterogeneous process.

  • 350.
    Koochaki, Mohammad Sadegh
    et al.
    Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran. Department of Environmental Science and Policy, Università degli Studi di Milano, Milan, Italy.
    Khorasani, Saied Nouri
    Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran.
    Neisiany, Rasoul Esmaeely
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Polymer Engineering, Hakim Sabzevari University, Sabzevar, Iran.
    Ashrafi, Ali
    Department of Material Engineering, Isfahan University of Technology, Isfahan, Iran.
    Magni, Mirko
    Department of Environmental Science and Policy, Università degli Studi di Milano, Milan, Italy.
    Trasatti, Stefano P.
    Department of Environmental Science and Policy, Università degli Studi di Milano, Milan, Italy.
    Facile strategy toward the development of a self-healing coating by electrospray method2019Inngår i: Materials Research Express, ISSN 2053-1591, Vol. 6, nr 11, artikkel-id 116444Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A self-healing anti-corrosion epoxy coating was prepared by the incorporation of dual capsule healing system. Microcapsules were prepared through the facile electrospray method by using Poly(styrene-co-acrylonitrile) polymer as shell material. Polyetheramine and Methylene diphenyl diisocyanate (MDI) based isocyanate prepolymer were utilized as core materials because of their high reactivity and low sensitivity in forming polyurea polymers. Scanning electron microscopy (sem) images confirmed the spherical morphology of the prepared microcapsules with average diameters of 0.93 ± 0.55 μm and 1.21 ± 0.68 μm for the encapsulated polyetheramine and isocyanate microcapsules, respectively. Moreover, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) results confirmed the successful encapsulation of both core materials with a high encapsulation yield (71% and 68% for Polyetheramine and MDI based isocyanate respectively). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization technique were used to assess the effects of utilizing the aforementioned system on the intrinsic anti-corrosion barrier property (on pristine samples ) and the self-healing efficiency (after cross scratching) of the resulting smart coatings. The corrosion assessment results confirmed the self-healing performance of the incorporated capsules along with a high healing efficiency (85%) for the optimum microcapsule content.

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