| 1. |
- Fernando, Dinesh, et al.
(författare)
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Subproject 2: Effect of using low-energy segments for producing TMP pulps at Braviken
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The effects of pressurized compressive chip and low dosage sulphite pretreatments were evaluated for production of thermomechanical pulp in mill scale trials using Norway spruce (Picea abies) at the Braviken paper mill (Holmen Paper AB, Sweden). The aim of the study was to provide knowledge leading to the improvement of energy efficiency during the production of mechanical pulps suitable for news and improved new grade papers. Pulps produced in the mill trials were characterized using conventional pulp and paper testing and by advanced methods including image analysis, FTIR with multivariate analysis, Simons staining with statistical analysis, spectral imaging and HCL fibre cleavage. Sulphite pre-treatment gave a linear dose response in tensile index and light scattering with addition of sulphite (≥ 1.2% Na2SO3). The maximum in tensile index and light scattering at a sulphur content of 0.2% (as Na2SO3) reported previously was not found in this mill study. Low dosage sulphite pre-treatment increased delamination/internal fibrillation of fibres indicating increased fibre flexibility. These fibres produced denser sheets with higher tensile index and slightly reduced light scattering at certain specific energy consumption. The specific energy consumption needed to produce pulp at a certain tensile index was reduced by 320 kWh/BDT (15%) for chips pre-treated with ~1.2% Na2SO3 compared with untreated chips. This gave a reduction in light scattering for sulphite pre-treated pulps when compared at equal tensile index. Image analysis of fibre cross-sections provided information of the composition of the total fibre population, fibre cross-sectional compactness as well as effects of sulphite treatment. Results showed a fairly constant fibre population (40% early-/60% latewood) existing in all samples and for higher energy to cause greater fibre splitting of untreated fibres particularly of latewood fibres. Increasing the amount of sulphite reduced fibre splitting with less severe fibre delamination for pulps refined at 1820 and 1850 KWh/ADT. Sulphite treatment seemed in general to induce more refining of early- than latewood fibres. SEM observation on fibres revealed high degree of deformation along the fibre axis that could also be seen on the fibre crosssections analyzed. FTIR analyses indicated that the highest degree of sulphonation (10 kg/BDT) gave rise to different fibre separation mechanisms during refining compared with the reference unsulphonated pulps providing a different fibre surface and thereby mechanical properties. Multivariate analysis of FTIR spectra suggested the exposed fibre surface to be richer in hemicellulose for sulphonated pulped fibres. This could provide for a better binding surface and higher strength for paper. However, no clear pattern of differences in the distribution images and therefore the microdistribution of xylan were determined. Statistical analysis of the Simons´ staining of fibres indicated that both the energy input and chip pre-treatment significantly induced wall delamination and internal fibrillation (D/IF) of pulp fibres. It was shown that the fibre development of pulp 10(1580) (with lowest SEC) gained via improved wall D/IF was almost similar to that shown for pulp 00(1850) (with highest SEC). This indicates that an energy efficient refining can be obtained with 10 kg/BDT sulfite pre-treatment prior to refining and will produce the most flexible fibres. Spectral imaging showed sulphite treatment of impressarefiner chips to improve the optical properties of pulps with a clear dose-response shown at both higher and lower SEC levels, the former having the largest effect on whiteness. Photochemical effects of sulfonation using reflectance intensities showed complex results regarding lignocellulosic autofluorescence. Unlike wood, impressarefiner chips and pulp fibres showed a clear blue-shifted fluorescence maximum characteristic for a shortened conjugated system indicating that both the chipping and Impressafiner pretreatment induced a minor degradation of the lignocellulosic matrix that can be measured using spectral imaging. Refining however, increased the red edge fluorescence of the sulfonated whole long fibre fraction with a similar effect on the lignin fluorescence of wood. Using the HCL method of fibre analysis no significant trend for the effect of sulphite treatment was noted and only minor differences in fibre length were detected.
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| 2. |
- Fernando, Dinesh, et al.
(författare)
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Characterization and biological depectinization of hemp fibers originating from different stem sections
- 2015
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Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 76, s. 880-891
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Tidskriftsartikel (refereegranskat)abstract
- The wide variation of mechanical properties of natural fibers limits their applications in matrix compos-ites. The aim of this study is to evaluate the properties of hemp fibers from different stem sections (top,middle and bottom) and to assess fungal retting pretreatment of hemp from different stem sections withthe white rot fungi Phlebia radiata Cel 26 and Ceriporiopsis subvermispora. For the untreated hemp fibers,no apparent difference in tensile behavior for fiber bundles from different stem sections was observed,and more than 90% tested samples demonstrated plastic flow behavior. Fiber strength and stiffness werehighest for the fibers from the top and middle stem sections. These properties were related to the compositional make up and morphological properties of hemp fibers, notably the secondary fiber cell contents.In fungal retting, there was a strong dependence of depectinization selectivity on stem section, whichdecreased from bottom to top presumably due to the significantly higher lignin content in the bottomsection than in the top section (middle section was in between). Consequently, the fungal retting caused alower reduction in strength of fibers from the bottom section than in those from the top stem section, andessentially reversed the influence of stem section on fiber tensile strength through depectinization selec-tivity. At whole hemp stem level, the fungal retting with P. radiata Cel 26 exhibited better mechanicalproperties with an ultimate tensile strength, strain and stiffness of 736 MPa, 2.3% and 42 GPa, respec-tively, while fibers treated with C. subvermispora exhibited lower mechanical properties of 573 MPa, 1.9% and 40 GPa, respectively. The study thus also showed that less variable and high strength fibers may beproduced using the dependence of depectinization selectivity on stem section for composite application
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| 3. |
- Fernando, Dinesh, et al.
(författare)
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Effect of harvest time and field retting duration on the chemical composition, morphology and mechanical properties of hemp fibers
- 2015
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Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 69, s. 29-39
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Tidskriftsartikel (refereegranskat)abstract
- The large variability in the mechanical properties of hemp fibers creates difficulties for using them in high-grade composites. The objective of the present study was to determine the optimal growth stage for harvesting hemp fibers for use in composites and to evaluate the effect of field retting time on mechanical performance of the fibers. Reduction in bast content and thickness of the primary bast fiber layer in stems were found to be highly significant (P ˂ 0.01) with plant maturity. A significant increase in the secondary fiber fraction occurred with maturity, reaching a maximum value of 10% at seed maturity. A highly significant reduction in cellulose deposition in fiber cell walls was reflected by reduced fiber wall thickness with plant maturity and was related to the development and ripening of hemp seeds. A statistically significant increase in lignin deposition and slight decrease in pectins in hemp fiber cell walls was also noted with stem maturity. Microscopy observations and histochemical analyses corroborated results from chemical analyses and showed variations in morphological aspects and spatial micro-distributions of carbohydrates and lignin within the cell structure of the hemp stems between early- and late growth phases. Fibers harvested at the beginning of flowering exhibited high tensile strength and strain, which decreased with plant maturity. Reduction in strength was related to the increase in proportion of secondary fibers and decrease in cellulose deposition leading to inferior properties of the primary fibers. A negative effect of field retting occurred only after long term field retting (i.e. 70 days) which was presumably due to accelerated degradation of cellulose by the action of microorganisms.
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| 4. |
- Ander, Paul, et al.
(författare)
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Sub-project 10: CRUW Mechanical Pulping Enzyme treatment of chips for energy reduction in TMP
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In order to evaluate the possibilities of using enzymes for pre-treating softwood chips as a means of lowering the energy demand in mechanical pulping, impregnation and refining trials were performed using a set of different enzymes. The enzymes tested pectinase, xylanase and mannanase gave increased sugar release in the impregnation trials indicating that most of the sugar released occurred in the first 60 minutes and that activities thereafter seemed to level off. Refining trials using a small Wing refiner showed that for chips treated for 60 minutes with pectinase, xylanase and mannanase no energy savings to a given freeness level was observed. The property development was similar to that of reference pulps in the case of pectinase and xylanase while for chips treated with mannanase a less favourable development of the tensile index was noted. For chips treated for two hours, using xylanase or pectinase, energy savings could be observed for pectinase treated chips down to a freeness level of 200 CSF. However when refined further, the properties approached those of the reference pulp. Considering the much higher enzymatic activity reached when the initial fibre material was further disintegrated it is assumed that the possibilities for enzymes to attack desired structures of the intact fibre wall may have been too few even in the case of Impressafiner treated material.
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| 5. |
- Daniel, Geoffrey
(författare)
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Decay capacity and degradation patterns of Xylaria hypoxylon on different wood species
- 2022
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Ingår i: Proceedings IRG Annual Meeting. - 2000-8953.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A host of physical and environmental factors may influence fungal decay including the wood substrate, temperature, moisture, oxygen, light, pH, and nitrogen. Understanding the effects of these factors on fungal decay is important for the effective utilization of wood decay fungi in biotechnological processes and for understanding the role of these organisms in global carbon cycling. The ascomycete Xylaria hypoxylon causes white rot of hardwoods, but remains relatively under-characterized. In this investigation, the decay capability of this fungus was studied using beech, hornbeam, oak and pine. Although Xylaria species are considered as causing white rot decay, Type II soft rot erosion was observed on hornbeam, Type I soft rot cavities were noted on beech, simultaneous rot was found on oak and selective rot on pine. Results indicated that both wood species and cell wall chemistry affected morphological decay patterns illustrating the relationships between fungal enzymatic capacity and wood cell wall structure/chemistry.
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| 6. |
- Daniel, Geoffrey
(författare)
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Fungal Degradation of Wood Cell walls
- 2016
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Ingår i: Secondary Xylem Biology; Origin, Functions, and Applications. - 9780128021859 ; , s. 131-168
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Bokkapitel (refereegranskat)abstract
- This chapter outlines the main morphological changes produced in wood cell walls following colonization and decay by white-, brown-, and soft rot fungi capable of the biomineralization of wood’s main structural components, namely, the cellulose, lignin, and hemicellulose. Lesser information is given on mold and blue-stain fungi. The main modes of attack by fungi from the different decay groups are described with examples from light and electron microscopy given. The main types of enzymatic and nonenzymatic systems used by fungi from the different groups are also briefly reviewed with correlation made with the types of decay produced in wood cell walls.
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| 7. |
- Daniel, Geoffrey
(författare)
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Microscope Techniques for Understanding Wood Cell Structure and Biodegradation
- 2016
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Ingår i: Secondary Xylem Biology : Origins, Functions, Applications. - 9780128021859 ; , s. 309-343
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Bokkapitel (refereegranskat)abstract
- Light and electron microscopy have contributed significantly to revolutionize our understanding of wood structure and its biodegradation. Light (bright field, optical, fluorescence, ultraviolet) microscopy remains the dominant type of wood analysis allowing for global and detailed information of native cellular structure and chemistry as well as degraded wood. Light and electron microscopy (scanning and transmission) techniques provide complementary information from global through tissue, cell, subcellular, and suborganelle levels with high spatial resolution not available using other approaches. Conventional scanning and transmission electron microscopy (SEM/TEM) and ancillary approaches (FE-SEM, ESEM, Cryo-SEM, Cryo-TEM, SEM-EDX, TEM-EDX, and rapid freezing approaches) have greatly improved our finite understanding of the structure of wood cell walls and polymers and of the different morphological forms of wood decay described from light microscopy. SEM and FE-SEM have allowed for the three-dimensional structure of wood to be explored and the intimate nanostructure of the microfibrils and microfibril aggregates within cell wall layers to be revealed as well as providing new details on the interaction of microbes and their mechanisms of decay. The advent of electron tomography techniques with FE-TEM should provide intimate high resolution three-dimensional imaging of wood ultrastructure and decay not possible previously. Additional imaging and analysis techniques that have been used to reveal aspects of wood (ultra)structure and chemistry (e.g., FTIR, Raman, XPS, ToF-SIMS, AFM, X-ray microtomography) continue to be developed and applied although the various light and electron microscopy approaches still remain the most widely used and influential. In this chapter an outline will be given on the main microscopy techniques applied for studies on wood (ultra)structure and wood decay with examples and limitations. Emphasis will also be given to sample preparation as this is a fundamental prerequisite for achieving optimal results with all microscopy approaches.
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| 8. |
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| 9. |
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| 10. |
- Daniel, Geoffrey
(författare)
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The saprotrophic wood-degrading abilities of Rigidoporus microporus
- 2015
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 49
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Tidskriftsartikel (refereegranskat)abstract
- Saprotrophic wood-decaying abilities ofRigidoporus microporus (Polyporales, Basidiomycota) syn. Rigidoporus lignosus and the structural alterations induced in wood blocks of Hevea bra-siliensis Muell. Arg were studied. Mass loss of wood blocks was analyzed after 3 and 6 months respectively and the patterns of decay by pathogenic and endophytic isolates of this fungus were investigated using light microscopy. Effects of temperature on growth of the isolates on malt extract agar were also investigated. The R. microporus isolated from a non-H. brasiliensis host caused the highest percentage mass loss (27.2% after 6 months), followed by isolates ED310 (21.1%) and M13 (15.7%), both collected from diseased H. brasiliensis plantations. The isolate initially identified as an endophyte showed very low saprotrophic wood decay capability (4.3% after 6 months). The optimal temperature for growth of the isolates was 30 °C; except for the endophytic isolate which showed highest growth at 25 °C. Wood samples degraded by the R. microporus isolates showed simultaneous attack of wood cell walls, typical of white rot fungi. Results of the study indicate variability in the wood degrading abilities of the isolates and the potential differences in their physiology are discussed. Our findings further support the need for a taxonomical revision of the Rigidoporus genus.
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