Wood and fibre properties of fertilized Norway spruce

Very intensive forest management is relatively unexplored in Sweden, and while there is interest in pursuing e.g. the use of fertilizers on selected areas, there is concern about the quality of the wood when growth rate increases. This thesis summarises three studies on wood and fibre properties of Norway spruce grown in two nutrient optimisation experiments and one study from a Norway spruce provenance trial in Sweden. The nutrient optimisation trials were located at 57'08'N, 14'45'E and at 64'07'N, 19'27'E. Increment cores (12 mm diameter) were sampled at breast height from three different treatments and a control. The treatments were irrigation, irrigation combined with liquid fertilization and solid fertilization. Density, microfibril angle, cell wall thickness and radial and tangential cell widths were measured on the wood samples and averages per annual rings and fibre property distributions were analysed. Density, microfibril angle, and cell wall thickness were clearly affected by fertilization. Density and cell wall thickness decreased due to fertilization and microfibril angle increased. Cell widths were moderately affected. Variables describing the inherent development from the pith, such as distance or ring number from pith and ring width, an expression of temporal growth rate and an indicator of varying amounts of earlywood and latewood, were the most important factors explaining differences in fibre properties. The provenance study was situated at 57'56'N, 5'39'E. The differences in density found between provenances were lower than differences caused by fertilization. The possible impact of intense commercial fertilization of Norway spruce for utilization in the pulp and paper industry is discussed

An Image Analysis Method to Measure Cross-Sectional Tracheid Dimensions on Softwood Increment Cores

Anatomical properties of wood affect the properties of wood products. In this paper, an automated image analysis method for measuring cross-sectional tracheid dimensions of softwood cores is presented. The images used were single slice, confocal reflected light microscope images. By the use of the proposed method, automatic measurements of radial and tangential lumen diameter, as well as radial cell-wall thickness, of almost all individual tracheids are obtainable

Characterisations of Kraft Pulp and Paper Properties from Acacia Auriculiformis A. Cunn. Ex Benth.- A Confocal Microscopy Analysis

This study was carried out to characterise the transverse dimensions of mechanically treated (beaten) kraft Acacia auriculiformis pulp (AAP) and mixed tropical hardwood commercial pulp (MTHCP) fibres using the fast and non-destructive method of optical sectioning ability of confocal laser scanning microscopy. Also included in the study are the determination of chemical constituents, fibre morphologies using the image analyser and the optimum pulping conditions. Laboratory handsheets were produced using pulps beaten at varying beating degrees using the PFI mill, and evaluated for their physical and mechanical properties. Established standards were followed throughout the study. Results from the chemical constituents and fibre morphology determinations for A. auriculiformis sample were within the comparable range of previous studies. Optimum kraft pulping conditions was achieved at 19% active alkali for A. auriculiformis wood chips with a 51.9% screened yield, 0.085% reject and Kappa number 19.1. Laboratory handsheets were produced from AAP and MTHCP fibres that were beaten using the PFI mill, at 3 beating degrees; 0, 5000 and 10000 revolutions. Generally, the AAP fibres exhibited comparable, if not better, physical and mechanical properties than MTHCP. As beating progressed, pulp freeness decreased with increasing drainage time. This has resulted the tensile strength, bursting strength, tearing resistance, and folding endurance to increase but an inverse for bulk and air permeance

Liquid uptake by fibrous absorbent materials

The thesis elucidates the mechanisms for fluid-material interactions within incontinence pads and helps to address the lack of understanding in this area. By providing a better understanding of liquid uptake by fibrous materials, the work will contribute to the design of better products for incontinence sufferers. A review of flow in porous media is presented covering the methods used to measure and model fluid transport, particularly relating to flow in textiles and other fibrous materials. The majority of the work described in the thesis focuses on the wicking properties of needle-felt fabrics. Such felts are used in reusable (washable) incontinence pads and also provide a simplified model for the more complex materials used in disposable products. An apparatus was designed, built, and used to measure wicking in textile materials. The simplified case of one-dimensional semi-infinite liquid uptake from an infinite reservoir was studied in detail for a range of felts. Mass uptake and wetted area were measured using a digital balance and camera. In particular, the impact on wicking of liquid temperature, sample orientation (horizontal, vertical and angles between), and felt compression were investigated. Wicking into textile materials is commonly understood using a simple capillary tube model for flow. To evaluate the application of capillary models the felt microstructure was examined. Encapsulated cross-sections of felt samples were prepared, and software written to identify fibres penetrating the plane of an examined section. While some aspects of liquid wicking, were found to be as expected from a simple capillary tube model, wicking appeared to be reduced in very open structured fibrous materials. It is suggested that this was due to the existence of unsaturated flow where only saturated flow was assumed. Considerable variation in liquid saturation was found in the samples during wicking

Production and characterisation of pine wood powders from a multi-blade shaft mill

Wood is an important raw material for the manufacture of consumer products and in achieving societal goals for greater sustainability. Wood powders are feedstock for many biorefining and conversion techniques, including chemical, enzymatic and thermochemical processes and for composite manufacture, 3D printing and wood pellet production. Size reduction, therefore, is a key operation in wood utilisation and powder characteristics, such as shape, particle size distribution and micromorphology play a role in powder quality and end-use application. While in a green state, the native chemical composition and structure of wood are preserved. Powders are commonly produced from wood chips using impact mills, which require pre-sized, pre-screened and pre-dried chips. These steps necessitate repeated handling, intermediate storage and contribute to dry matter losses, operation-based emissions and the degradation of the wood chemistry.This thesis investigated a new size reduction technology, known as the multi-blade shaft mill (MBSM). The MBSM performance was studied through the milling of Scots pine (Pinus sylvestris L.) wood using a designed series of experiments and through modelling with multi-linear regression (MLR) analyses. Light microscopy combined with histochemical techniques were used to investigate particle micromorphology and distribution of native extractives in powders. The aim was to evaluate the technical performance of the MBSM with relation to operational parameters, to characterise the produced powders and to evaluate the technology through comparison with impact milling.The results showed that the MBSM could effectively mill both green and dry wood. Produced powders showed distinct differences compared to those obtained using a hammer mill (HM). The specific milling energy of the MBSM was lowest for green wood and within the range of other established size reduction technologies. However, much narrower particle size distributions were observed in MBSM powders and they had significantly greater amounts of finer particles. Particles with high aspect ratio and sphericity were a characteristic of MBSM powders and this Production and characterisation of pine wood powders from a multi-blade shaft mill was true for wood milled above and below its fibre saturation point. MBSM powders from green wood showed evidence of higher specific surface area, larger pore volume and greater micropore diameter than those from HM powder. Preliminary microscopic examination suggested that cell walls in MBSM powders showed evidence of retaining their original native wood structure. Consequently, their extractive content appeared intact. This was in contrast to HM powder and it may reflect the differences between the two size reduction mechanisms. According to the produced MLR models, the results suggest that MBSM milling is more akin to a sawing process and opposite to that of impact-based mills

The influence of different chemical treatments on the mechanical properties of hemp fibre-filled polymer composites

The fluctuation of engineering and general-purpose polymer prices, rapid exhaustion of fossil fuel world-wide reserves and heightened awareness about environment have led the research community to explore the use of natural biodegradable raw materials as substitutes for manmade resources. Natural fibres are considered as substitutes for synthetic fibres in reinforced polymer matrix composites. Increased interest has been shown in natural fibres from plants such as cotton, jute, hemp as replacements for aramid, glass, and carbon fibres. This is due to their biodegradability, low cost, low density, and satisfactory strength to weight ratio. However, they present certain disadvantages compared to synthetic fibres which include high moisture sorption rates, low durability, and weak fibre/matrix bonding strength. The poor adhesion between natural fibres and polymer matrices leads to poor mechanical properties for natural fibre reinforced composites. Improvement of the fibre/matrix interface is required to increase the mechanical properties of the natural fibre filled polymer composite In this study, the influence of selected chemical treatments on the mechanical properties of hemp-filled epoxy composites was investigated. The aim of this study was to enhance fibre/matrix interface and hence the mechanical properties of hemp yarn-reinforced epoxy composites by modifying the chemical nature of a high crystallinity hemp yarn through chemical treatments such as alkalization, silanization (3-aminopropyltriethoxysilane) and a maleic anhydride treatment. The effectiveness of the chemical treatments was assessed by means of XRD, FTIR and TGA. Density measurements of as-received yarns (1.42-1.45 g cm-3 ) were within the range reported in the literature. Crystallinity measurements revealed the astreated yarns as having high crystallinity indices (87% weft and 84.7 warp yarns). The surface treatments used increased the crystallinity index only slightly. A decision was taken to use warp yarns (UTS = 799 MPa) rather than warp yarns (UTS = 503 MPa). Silane treatment reduced the tensile strength of yarns slightly (753 MPa) while the treatment of the fibres with maleic anhydride (562 MPa) and alkali treatment (518 MPa) had a much more significant effect on ultimate tensile strength. By contrast the modulus of the treated yarns all increased compared to the as-received yarns. Silanization was confirmed by energy dispersive X-ray spectroscopy while maleation was confirmed by the presence of characteristic absorbances in FTIR spectra. TGA revealed that silanization improved fibre thermal stability while maleic anhydride treatment did the opposite, possibly due to decarboxylation reactions. Four type of fibre/matrix interfaces, based on the treated and non-treated fibres, were generated through the production of the hemp reinforced epoxy composite plates. The results showed insignificant variations in the mechanical and thermal properties compare with the as-received hemp-filled epoxy composites which showed the high mechanical properties and thermal stability. The silanization and alkalization slightly decreased the properties of their respective properties although this was deemed statistically insignificant. The maleic anhydride treatment worsened the mechanical properties significantly. Scanning electron microscopy revealed appreciable fibre-matrix debonding which is indicative of a weak fibre/matrix interface. This was postulated as a reason for the lack of any significant reinforcement of the epoxy composites by maleic anhydride treated fibres. The tensile properties were also predicted and no statistically significant differences were observed although the experimental strengths values appeared to be lower than the predicted strengths. In general, the lack of appreciable improvement in mechanical properties of as-received fibres was concluded to be due to the initially high crystallinity of the as-received fibres. This provided little scope for further alkalization to change the surface significantly as little further removal of hemicellulose and lignin could occur

Single fiber properties - a key to the characteristic defibration patterns from wood to paper fibers

This study approaches the phenomena of thermomechanical defibration of wood by examining single fiber properties. A hypothesis was formed based on literature: The defibration patterns due to impacts during fiber separation and high-consistency refining are related to the morphological properties of fibers. This is because: The effects caused by the action of defibration vary in morphologically different fibers, and The defibration action in the plate gap is influenced by the properties of the fiber material in the plate gap and changes as the properties of the fiber material in the plate gap change. In other words: the character of the fiber material affects the defibration result through two routes: firstly the defibration patterns of fibers are related to their properties, and secondly the character of the fiber bed in the plate gap influences the defibration action. The defibration patterns of fiber shortening, fiber wall thickness reduction and changing of fiber wall internal structure are discussed. The experimental part focuses on the defibration effects which are the measurable deformations in the fibers as a result of defibration actions. Defibration patterns are a set of defibration effects that develop the stiff wood fibers into papermaking fibers and fines particles. These concepts can be applied to all mechanical pulping processes, but this thesis focuses on their application to the TMP process and spruce as raw material. Fiber shortening was the result of cutting of fibers during the fiber separation stage. Fast-grown and thinner-walled fibers were more resistant than thick walled slow growth fibers towards the harsh conditions prevailing during fiber separation. Faster warming up of the fiber wall as a result of compression and relaxation of the material as well as encountering fewer shear forces than thick-walled incompressible fiber material were suggested as explanations for the different response of these fibers. The gradual peeling off of layers from the fiber surface resulted in reduction of fiber wall thickness. Different types of fibers produced different types of fines. The fibrillar fines were formed mainly from thick-walled fibers, and 50-100% of the fibrillated fibers originated from latewood. The flake-like fines originated both from outer layers of latewood and earlywood fibers during fiber separation stage but also from pieces of the thinwalled earlywood fibers during the later stages of the whole defibration process. Only half of the fines fraction was formed as a result of peeling off of fiber wall. The rest consisted of ray cells, pieces of fibers and fiber wall formed as a result of fiber cutting or splitting. The differences in the fiber wall thickness did not explain the flexibility differences between initially refined and highly refined samples. From this was concluded that the fiber wall flexibility increased and fiber wall structure loosened during the defibration. Local swelling of the fiber wall was revealed using optical sectioning by confocal laser scanning microscopy. As a result of this inhomogeneity both fiber wall swelling and fiber conformability varied along the fiber length. Removal of the outer fiber layers increased fiber flexibility by decreasing fiber elastic properties and lowering the moment of inertia