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  • 51.
    Sjökvist, T.
    et al.
    Linnaeus Univ, Dept Forestry & Wood Technol, SE-35195 Vaxjo, Sweden..
    Wålinder, Magnus E.P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Blom, A.
    Linnaeus Univ, Dept Forestry & Wood Technol, SE-35195 Vaxjo, Sweden..
    Liquid sorption characterisation of Norway spruce heartwood and sapwood using a muiticycle Wilhelmy plate method2018In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 9, no 2, p. 58-65Article in journal (Refereed)
    Abstract [en]

    A multicycle Wilhelmy plate method was applied to study the water and octane sorption behaviour of small Norway spruce veneers. Dry heart- and sapwood samples of varying density were investigated. The results showed a correlation between the porosity and the sorption of octane for all samples, i.e. a higher wood porosity resulted in higher octane sorption. However, no difference in octane sorption was found between heart- and sapwood samples of similar density. The water sorption behaviour was difficult to interpret, probably due to the influence of surface-active wood extractives. It is suggested that the presence of such extractives, particularly in the sapwood samples, increases the sorption of water due to a significant decrease in its apparent surface tension. Hence, the results indicate that the liquid water sorption of spruce heart- and sapwood is strongly influenced by variations in the extractives content rather than by the micromorphology.

  • 52.
    Stehr, Micael
    KTH, Superseded Departments, Solid Mechanics.
    Adhesion to machined and laser ablated wood surfaces1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis is a contribution to the R&D-program ValueActivation at KTH,Division of Wood Technology and Processingand containsfive papers related to the evaluation and development ofmachining techniques (mechanical and irradiation treatments)whereby weak boundaries at the wood surfaces in the form of(mechanical) weak boundary layers and (micro) cracks due tomechanical treatment can be avoided.

    The first paper describes the development of a method–using a UV laser–to study the mechanically weakenedboundaries. The purpose is to achieve a sample preparationtechnique for microscopy that minimizes artefacts.

    Scientifically, the second, third and fourth papers,concerning the interaction between wooden surfaces andsynthetic polymers, are based on the relatively modern adhesiontheory (at least in the field of wood adhesion science) of weakboundary layers. The papers introduce and evaluate the(mechanical) weak boundary layers in relation to wood adhesionscience. The first of these three papers provides thetheoretical basis for the following two. The paper suggests adivision of the weak boundary layer concept into chemical(CWBL) and mechanical (MWBL) weak boundary layers. Thesubsequent two papers evaluate the influence on the glue jointstrength of a reduction in the (mechanical) weak boundarylayer.

    The last paper deals with (tip-)cracks on a wood surface dueto machining.

    The results presented in the first paper can be used toachieve samples for microscopic investigations with a minimizednumber of artefacts. The results presented in the fourth papercould be utilized to achieve stronger adhesive joints. Withhelp of a laser ablation technique, it is shown that the "lawof nature" saying that end-grain surfaces cannot be glued ismaybe not so obvious. Methods of eliminating or reducing theweak boundaries have been identified. The results indicate thatit is the adhesive itself that is the weak point in anend-grain joint.

    It is also possible that the laser ablation techniqueapplied on flat sides could lead to better adhesion between acoating and wood, and the results presented in the last papercould increase the adhesive performance particularly related tocoatings.

  • 53.
    Stevanic, Jasna S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Bergström, Elina Mabasa
    Gatenholm, Paul
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Salmén, Lennart
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Arabinoxylan/nanofibrillated cellulose composite films2012In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, no 18, p. 6724-6732Article in journal (Refereed)
    Abstract [en]

    There is an increasing interest in substituting petroleum based polymer films, for food packaging applications, with films based on renewable resources. In many of these applications, low oxygen permeability and low moisture uptake of films are required, as well as high enough strength and flexibility. For this purpose, rye arabinoxylan films reinforced with nanofibrillated cellulose was prepared and evaluated. A thorough mixing of the components resulted in uniform films. Mechanical, thermal, structural, moisture sorption and oxygen barrier characteristics of such films are reported here. Reinforcement of arabinoxylan with nanofibrillated cellulose affected the properties of the films positively. A decrease in moisture sorption of the films, as well as an increase in stiffness, strength and flexibility of the films were shown. From these results and dynamic FTIR spectra, a strong coupling between reinforcing cellulose and arabinoxylan matrix was concluded. Oxygen barrier properties were equal or better as compared to the neat rye arabinoxylan film. In general, the high nanofibrillated cellulose containing composite film, i.e. 75 % NFC, showed the best properties.

  • 54.
    Stevanic Srndovic, Jasna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ultrastructure of the Primary Cell Wall of Softwood Fibres Studied using Dynamic FT-IR Spectroscopy2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The primary cell wall is a complex multipolymer system whose composite structure has been mostly determined from chemical and biochemical studies. Although the primary cell wall serves a central role, with regard to the connective properties of fibres, knowledge about the interactions among the polymers, when it comes to the mechanical properties, is very limited. The physical properties of the polymers, i.e. their elastic and viscous deformations, as well as the ultrastructure of the polymers, i.e. the interactions among the polymers in the outer fibre wall layers that lead to this behaviour, are still not fully understood.

    The aim of this study was to examine how the different wood polymers, viz. lignin, protein, pectin, xyloglucan and cellulose, interact in the outer fibre wall layers of the spruce wood tracheid. The initial objective was to separate an enriched primary cell wall material from a first stage TMP, by means of screening and centri-cleaning. From this material, consisting of the primary cell wall (P) and outer secondary cell wall (S1) materials, thin sheets were prepared and analysed using a number of different analytical methods. The major measuring technique used was dynamic Fourier transform infra-red (FT-IR) spectroscopy in combination with dynamic 2D FT-IR spectroscopy. This technique is based on the detection of small changes in molecular absorption that occur when a sinusoidally stretched sample undergoes low strain. The molecular groups affected by the stretching respond in a specific way, depending on their environment, while the unaffected molecular groups provide no response to the dynamic spectra, by producing no elastic or viscous signals. Moreover, the dynamic 2D FT-IR spectroscopy provides useful information about various intermolecular and intramolecular interactions, which influence the reorientability of functional groups in a polymer material.

    Measurements of the primary cell wall material, using dynamic FT-IR spectroscopy, indicated that strong interactions exist among lignin, protein and pectin, as well as among cellulose, xyloglucan and pectin in this particular layer. This was in contrast to the secondary cell wall, where interactions of cellulose with glucomannan and of xylan with lignin were dominant. It was also indicated that the most abundant crystalline cellulose in the primary cell wall of spruce wood fibres is the cellulose Iβ allomorph, which was also in contrast to the secondary cell wall, where the cellulose Iα allomorph is more dominant. The presence of strong interactions among the polymers in the primary cell wall and, especially, the relatively high content of pectin and protein, showed that there is a very good possibility of selectively attacking these polymers in the primary cell wall. The first selective reaction chosen was a low degree of sulphonation, applied by an impregnation pretreatment of chips with a very low charge of sodium sulfite (Na2SO3). This selective reaction caused some structural modification of the lignin, a weakening of the interactions between lignin;pectin, lignin;protein and pectin;protein, as well as an increased softening of the sulphonated primary cell wall material, when compared to the unsulphonated primary cell wall material. All this resulted in an increased swelling ability of the material.

  • 55.
    Stevanic Srndovic, Jasna
    et al.
    STFI-Packforsk, Swedish Pulp and Paper Research Institute.
    Salmén, Lennart
    STFI-Packforsk, Swedish Pulp and Paper Research Institute.
    Characterizing wood polymers in the primary cell wall of Norway spruce (Picea abies (L.) Karst.) using dynamic FT-IR spectroscopy2008In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 15, no 2, p. 285-295Article in journal (Refereed)
    Abstract [en]

    Dynamic Fourier Transform Infra-Red (FT-IR) spectroscopy was used to examine the interactions among cellulose, xyloglucan, pectin, protein and lignin in the outer fibre wall layers of spruce wood tracheids. Knowledge regarding these interactions is fundamental for understanding the fibre separation in a mechanical pulping process. Sheets made from an enriched primary cell wall material were used for studying the viscoelastic response of the polymers. The results indicated that strong interactions exist among lignin, protein, pectin, xyloglucan and cellulose in the primary cell wall. This signified a closely linked network structure of the components on the fibre surface. This ultrastructural arrangement in the primary cell wall and the relatively high content of lignin, pectin and protein in it, means that the primary cell wall is more submissive to selective chemical attacks, when compared to the secondary cell wall. A low ratio of cellulose I alpha to cellulose I beta in the primary cell wall was also found.

  • 56.
    Stevanic Srndovic, Jasna
    et al.
    STFI-Packforsk, Swedish Pulp and Paper Research Institute.
    Salmén, Lennart
    STFI-Packforsk, Swedish Pulp and Paper Research Institute.
    Interactions among Components in the Primary Cell Wall of Norway Spruce (Picea Abies (L.) Karst.): Effect of a Low Sulphonation Pretreatment2008In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 34, no 2, p. 107-112Article in journal (Refereed)
    Abstract [en]

    Dynamic Fourier Transform Infra-Red (FT-IR) spectroscopy was used to examine the effect of a low sulphonation treatment on the ultrastructure of the primary cell wall of spruce wood. Sheets made from enriched primary cell wall material coming from a low sulphonated thermomechanical pulp were used for studying the viscoelastic response of the polymers using dynamic FT-IR spectroscopy. The overall ultrastructure of the primary cell wall remained largely unaltered, due to the exceptionally low degree of sulphonation used. However, an increased softening of the material as well as a weakening of the lignin,pectin, lignin, protein and pectin, protein interactions were observed. The suggestion is that, together with a structural modification of the lignin, it is the increased viscoelasticity of the material, resulting from the breaking down of the interactions among the polymers, that is the cause for the lower energy demand, when refining correspondingly low sulphonated chips.

  • 57.
    Stevanic Srndovic, Jasna
    et al.
    STFI-Packforsk.
    Salmén, Lennart
    STFI-Packforsk.
    The primary cell wall studied by dynamic 2D FT-IR: Interaction among components in Norway spruce (Picea abies)2006In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 40, no 9-10, p. 761-767Article in journal (Refereed)
    Abstract [en]

    Knowledge on the interactions among the wood polymers, viz. cellulose, hemicellulose, pectin, lignin and protein, in the outer fibre wall layers is essential for understanding fibre separation in thermomechanical and chemithermomechanical pulping processes. For this reason, dynamic two-dimensional Fourier Transform Infra-Red (2D FT-IR) spectroscopy was applied to examine the interaction of these components in the primary cell wall of spruce fibres. Sheets made of an enriched primary cell wall material were used for studying the viscoelastic response to loading. The dynamic 2D correlation FT-IR spectra indicated the existence of strong interactions between lignin and protein, as well as among pectin, xyloglucan and cellulose, in the primary cell wall. This is in contrast to the picture for the secondary cell wall, in which cellulose-glucomannan and xylan-lignin interactions are prevailing.

  • 58. Svedström, Kirsi
    et al.
    Bjurhager, Ingela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Kallonen, Aki
    Peura, Marko
    Serimaa, Ritva
    Structure of oak wood from the Swedish warship Vasa revealed by X-ray scattering and microtomography2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 3, p. 355-363Article in journal (Refereed)
    Abstract [en]

    The degradation of oak wood of the historical warship Vasa was studied, focusing on cellular structure by X-ray microtomography (mu CT) and on the nanostructure of the cell wall by wide- and small-angle X-ray scattering (WAXS, SAXS). Solid samples [polyethylene glycol (PEG)-, impregnated and PEG-extracted] were submitted to X-ray analysis and the results compared to those of recent oak. The cellular structure of the Vasa oak was surprisingly well preserved at the micrometer level, according to the mu CT images. As revealed by WAXS, the fraction of crystalline cellulose was lower in the Vasa samples compared with recent oak, but the average length and width of cellulose crystallites (25 +/- 2 nm and 3.0 +/- 0.1 nm, respectively), and the mean microfibril angles (4-9 degrees), showed no significant differences. Accordingly, the crystalline parts of cellulose microfibrils are well preserved in the Vasa oak. The SAXS results indicated a declined short-range order between the cellulose microfibrils and a higher porosity of the Vasa oak compared with recent oak, which may be explained by modification of the hemicellulose-lignin matrix.

  • 59.
    Tagami, Ayumu
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. Nippon paper Industries Co., Ltd..
    Gioia, Claudio
    University of Bologna.
    Lauberts, Maris
    Latvian State Institute of Wood Chemistry.
    Budnyak, Tetyana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Moriana, Rosana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. HIS-University of Skövde.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Solvent fractionation of softwood and hardwood kraft lignins for more efficient uses: compositional, structural, thermal, antioxidant and sorption propertiesManuscript (preprint) (Other academic)
    Abstract [en]

    This work summarizes the impact of solvent fractionation on the chemical structure, antioxidant activity, heating values, and thermal and sorption properties of industrial hardwood and softwood kraft lignins. The aim was to develop a simple approach for the obtaining of lignin fractions with a tailored properties for the certain material applications.  Four common industrial solvents, namely, ethyl acetate, ethanol, methanol and acetone, in various combinations efficiently separated both spruce and eucalyptus kraft lignins into fractions with low polydispersities. The ethanol fraction of spruce and the ethyl acetate fraction of eucalyptus afforded the highest yields. Gel-permeation chromatography analysis was used to evaluate the efficiency of the chosen solvent combination for lignin fractionation. The composition and structure of the lignin material was characterized by elemental analysis, analytical pyrolysis (Py-GC/MS/FID) and 31P NMR spectroscopy. The thermal properties of the lignin samples were studied by thermogravimetric analysis. Proximate analysis data (ash, volatile components, organic matter and fixed carbon) were obtained through the direct measurement of weight changes in each experimental curve, and the high heating values (in MJ/kg) were calculated according to equations suggested in the literature. The sorption properties of fractionated kraft lignins were studied with respect to methylene blue dye. The clear correlation between certain structural features in the lignin fractions and the properties of the lignin provides useful information for selecting the appropriate solvent combinations for specific applications of lignin raw materials, including as antioxidants, biofuels or sorbents in water treatment processes.

    The full text will be freely available from 2019-09-14 15:00
  • 60. Thunberg, Johannes E.
    et al.
    Westman, Gunnar
    Gatenholm, Paul
    Wallenberg Wood Sci Ctr, Chalmers, Sweden.
    Cellulose nanofibers electrospun from non volatile ionic liquid2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Article in journal (Other academic)
  • 61. Trovatti, E.
    et al.
    Cunha, A. Gisela
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Carvalho, A. J. F.
    Gandini, A.
    Furan-modified natural rubber: A substrate for its reversible crosslinking and for clicking it onto nanocellulose2017In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 95, p. 762-768Article in journal (Refereed)
    Abstract [en]

    The conventional vulcanization process applied to elastomers is irreversible and hinders therefore their useful recycling. We demonstrate here that natural rubber can be reversibly crosslinked via the Diels-Alder coupling of furan and maleimide moieties. The furan-modified natural rubber used in this strategy was also exploited to bind it to maleimide-modified nanocellulose, thus generating a covalently crosslinked composite of these two renewable polymers.

  • 62. Uetimane, Ernesto, Jr.
    et al.
    Allegretti, Ottaviano
    Terziev, Nasko
    Söderström, Ove
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Application of non-symmetrical drying tests for assessment of drying behaviour of ntholo (Pseudolachnostylis maprounaefolia PAX)2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 3, p. 363-368Article in journal (Refereed)
    Abstract [en]

    Experiments concerning drying behaviour of ntholo (Pseudolachnostylis maprounaefolia PAX) were conducted to find a suitable drying schedule. Two non-symmetrical drying (NSD) tests were carried out to determine the drying behaviour of ntholo in terms of drying rate and stress behaviour. A tentative drying schedule was selected for comparison of the test results with those of similar tests with other known species. The schedule was tested in a laboratory kiln on 28-mm thick boards. According to both NSD tests and laboratory tests, ntholo dries easily but slowly. The laboratory drying lasted 266 h and achieved standard drying quality characterised by 8.9% moisture content, a moisture gradient of 1.2% and a case-hardening (gap) of 1.2 mm. Twist was the largest deformation with 3.4 mm per 1000 mm on average. The assigned schedule provided standard drying quality and it could be tested further in industrial kilns.

  • 63. Vahtikari, Katja
    et al.
    Rautkari, Lauri
    Noponen, Tuula
    Lillqvist (nee Laine), Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Hughes, Mark
    The influence of extractives on the sorption characteristics of Scots pine (Pinus sylvestris L.)2017In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, no 18, p. 10840-10852Article in journal (Refereed)
    Abstract [en]

    The sorption behaviour of extracted and un-extracted Scots pine (Pinus sylvestris L.) heartwood was analysed using dynamic vapour sorption apparatus. In addition to the sorption isotherm and hysteresis, the moisture increments and decrements were determined as well as the rate of sorption. Parallel exponential kinetics model was used for further analysis. The effect of cyclic humidity loading on the sorption characteristics was studied by exposing samples to ten repeated sorption cycles and by determining the amount of accessible hydroxyl (OH) groups before and after the cyclic humidity loading. Removal of extractives led to an increase in EMC both in adsorption and in desorption. Hysteresis decreased due to the removal of extractives. Cyclic humidity loading reduced the sorptive capacity of wood material for both extracted and un-extracted wood, but was more pronounced in un-extracted wood. However, despite the decrease in the sorptive capacity, the amount of accessible OH groups increased after ten repeated dry-humid cycles.

  • 64.
    Winzell, Anders
    et al.
    KTH, School of Biotechnology (BIO).
    Rajangam, Alex
    KTH, School of Biotechnology (BIO).
    Arvestad, Lars
    KTH, School of Computer Science and Communication (CSC).
    Filling, Charlotta
    KTH, School of Biotechnology (BIO).
    Divine, Christina
    KTH, School of Biotechnology (BIO).
    Aspeborg, Henrik
    KTH, School of Biotechnology (BIO).
    Master, Emma R.
    KTH, School of Biotechnology (BIO).
    Teeri, Tuula T.
    KTH, School of Biotechnology (BIO).
    Sequence Analysis and Recombinant Expression of Family 43 GlycosyltransferasesManuscript (preprint) (Other academic)
  • 65. Wojtasz-Mucha, J.
    et al.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hydrothermal pretreatment of wood by mild steam explosion and hot water extraction2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 241, p. 120-126Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to compare the two most common hydrothermal pre-treatments for wood – mild steam explosion and hot water extraction – both with the prospect of enabling extraction of hemicelluloses and facilitating further processing. Although both involve autohydrolysis of the lignocellulosic tissue, they are performed under different conditions: the most prominent difference is the rapid, disintegrating, discharge employed in the steam explosion opening up the structure. In this comparative study, the emphasis was placed on local composition of the pre-treated wood chips (of industrially relevant size). The results show that short hot water extraction treatments lead to significant variations in the local composition within the wood chips, while steam explosion accomplishes a comparably more even removal of hemicelluloses due to the advective mass transport during the explosion step.

  • 66.
    Zheng, Chao
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Cellulose-fiber-based thermal insulation materials with fungal resistance, improved water resistance and reaction-to-fire properties2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermal insulation materials made from natural fibrous materials, such as cellulose fibers, have advantages over others from a sustainability point of view. However, cellulosic materials are generally prone to mold and absorb moisture, and these have negative effects on the insulation properties, the durability of insulation materials, and interior air quality. In this thesis, cellulose-fiber-based insulation foams were prepared from bleached chemithermomechanical softwood pulp, and these foams showed promising thermal insulation properties and fungal resistance. Hydrophobic extractives were isolated from birch (Betula verrucosa) outer bark and used to improve the water resistance of the foams, which were impregnated in solutions of extractives and then dried. The modified foams showed greater water resistance, and the modification had no negative effects on the thermal insulation, fungal resistance, and compressive strength of the foams.

    Another potential problem with low density cellulosic thermal insulation materials is their poor reaction-to-fire properties. Cellulose-fiber-based insulation foams were prepared from formulations containing bleached chemithermomechanical softwood pulp and commercial fire retardants to improve the reaction of the foams to fire. Single-flame source test results showed that the foams containing 20% expandable graphite (20% EG) or 25% synergetic (25% SY) fire retardant had significantly improved reaction-to-fire properties and passed class E, which reflected that they can resist a small flame attack without substantial flame spreading for a short period according to EN 13501-1. Compared with the reference without any fire retardant, the peak heat release rate (Peak-HRR) of the 20% EG and 25% SY decreased by 62% and 39% respectively when the samples were subjected to a radiance heat flow of 25 kW m-2 in a Cone Calorimeter.

    The thesis demonstrates that it is possible to produce cellulose-fiber-based insulation materials with improved properties in terms of fungal, improved water resistance and reaction-to-fire properties.

  • 67.
    Zheng, Chao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Cellulosic Thermal Insulation with Improved Water Resistance and Fire Retardancy2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sweden is one of the largest countries by area in Europe, and almost 70% of it is covered by forest. These abundant forest resources benefit the Swedish bioeconomy, but the pulp and paper industry is facing the challenge of a decrease in the demand for printing paper due to a significant shift to electronic media; therefore, it is a priority to use pulp to produce alternative value-added products, such as thermal insulating materials in buildings. Cellulosic thermal insulation can reduce the heating energy consumption of buildings, and decrease the emission of CO2, thus contributing to a sustainable society.

    However, cellulosic thermal insulation needs to overcome its poor water resistance, to lower the risk of fungi and ensure a good interior air quality. In the work described in this thesis, cellulosic insulation materials have been produced from pulp fibers, water, and foaming agent by a foam-forming technique. Hydrophobic extractives isolated from birch outer bark were used to functionalize the insulating materials. These materials showed an improved water resistance due to the intrinsic non-polarity of the extractives, promising thermal insulation properties and fungal resistance.

    Fire retardancy is another challenge for cellulosic thermal insulation, and cellulosic insulation materials were here prepared from formulations containing pulp and commercial fire retardants. Fire test results showed that the materials containing 20% expandable graphite or 25% synergetic fire retardant had a significantly improved fire retardancy, being able to resist a small flame attack for a short period without substantial flame spreading. A study of the mechanism of fire retardancy confirmed that the fire retardants can catalyze the dehydration of pulp and promote the generation of a protective char layer that prevents the materials from further decomposition.

    Bio-based fire-retardant coatings such as sulfonated kraft lignin and nanoclay can provide a more efficient fire-retardant protection on the cellulosic insulation than a fire retardant incorporated in the materials. A nanoclay coating performed the best because of its very good thermal stability. The effective bio-based fire-retardant coating is promising for future use in cellulosic thermal insulation materials.

    The full text will be freely available from 2019-09-14 13:57
  • 68.
    Zheng, Chao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants2018In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926Article in journal (Refereed)
    Abstract [en]

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

  • 69.
    Zheng, Chao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Li, Dongfang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Cellulose-fiber-based insulation materials with improved reaction-to-fire properties2017In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 3, p. 466-472Article in journal (Other academic)
    Abstract [en]

    The poor reaction-to-fire properties of cellulosic thermal insulation need to be improved to meet the safety regulations for building materials. In this study, cellulose-fiber-based insulation foams were prepared from formulations containing mechanical pulp and commercial fire retardants. Results of single-flame source tests showed that foams developed from the formulations with 20% expandable graphite (EG) or 25% synergetic (SY) fire retardants had substantially improved reaction-to-fire properties, and passed fire class E according to EN 13501-1. The results indicated that the foams could resist a small flame attack without serious flame spreading over a short period of time. Compared with the reference foam that contained no fire retardant, the peak heat release rate of the 20% EG and 25% SY foams decreased by 62% and 39% respectively when the samples were subjected to a radiance heat flux of 25 kW m-2 in a cone calorimeter, which suggested enhanced reaction-to-fire properties of these foams.

  • 70.
    Zheng, Chao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Dongfang
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardantsManuscript (preprint) (Other academic)
    Abstract [en]

    Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m2. Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m2, as shown by cone calorimetry and single- flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications as sustainable thermal insulating materials for improved fire retardancy.

  • 71.
    Zheng, Chao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Dongfang
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ottenhall, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Cellulose fiber based fungal and water resistant insulation materials2017In: International Journal of the Biology, Chemistry, Physics, and Technology of Wood, E-ISSN 1437-434XArticle in journal (Refereed)
    Abstract [en]

    The development of thermal insulation materials from sustainable, natural fibrous materials is desirable.In the present study, cellulose fiber based insulation foams made of bleached chemi thermo mechanical pulp(CTMP) have been investigated. To improve water resistance, the foams were impregnated with hydrophobic extractives from the outer bark of birch (Betula verrucosa)and dried. The surface morphology of the foams and the distribution of the deposited particles from the extractives were observed by scanning electron microscopy (SEM).The modified foams showed improved water resistance, as they did not disintegrate after immersion in water for7 days, whereas the unmodified foam did. Compared to the unmodified foam, the modified foams absorbed 50%less moisture within 24 h. The modification had no negative effects on the thermal insulation properties, fungal resistance or compressive strength of the foams. The proposed approach is simple and can be easily integrated into plants working based on the biorefinery concept.

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