| 1. |
- Larsson, Magnus, 1976-, et al.
(författare)
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Contextual Engineering of Materials: Optimisation of a Wood/Glass Wall Based On Weighted Objectives
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Ingår i: International Wood Products Journal. - 2042-6445 .- 2042-6453.
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Tidskriftsartikel (refereegranskat)abstract
- This paper challenges an asserted artificial separation between architecture, engineering, and material design. Novel protocols for mass-customised building materials could make each material entity perform optimally at its given position within a geometry. The number of evaluated materials in an architectural surface should be expanded to become equal to its number of parts. This number should in turn be maximised given other constraints and objectives. The built environment’s restricted material palette provides a limited space of possible combinations of material properties. Evolutionary design procedures could expand this conservative range of materials to achieve additional performance targets. Contextual Optimisation Workspace (COW) is a design tool that promotes such novel processes. Fusing multiple-objective optimisation (MOO) strategies with genetic algorithms, the system allows for analytical comparisons between conflicting aspects of a design. An experiment is conducted to investigate and develop two specific parts of the system’s anatomy. New components add weights to objectives while punishing less favourable designs. The components guide the relative positioning of wood products within a single wall of an architectural structure, to achieve optimal performance given predefined targets. A path towards a “contextual materials engineering technology” is discussed, and suggestions for future studies provided.
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| 2. |
- Larsson, Magnus, 1976-
(författare)
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Evolutionary Materialism: Towards a Theory of Anticipatory Adaptive Assemblages
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is an investigation into how meta-heuristic multi-objective optimisation processes (genetic algorithms driven by evolutionary solvers) can bring about materials-related advantages in architectural performance. It redefines the architect’s and engineer’s role from being designers of a singular space or structure to being designers of entire species of spaces, and discusses a particular method – anticipatory adaptive assemblages (AAA) – that allows such processes to produce many generations of design iterations that eventually yield individuals optimised for a set of predefined objectives. This includes in particular the optimisation of building materials, with a certain focus on timber structures.The thesis provides a theoretical foundation (assemblage theory) that connects an ontology, a methodology, an epistemology, and an axiology to the computational operations used, elevating the domain beyond simplistic notions of parametricism. It leverages contemporary generative design methods to introduce a range of novel concepts and tools such as auxiliary loads, material phase transition (MPT) diagrams, generative life cycle assessments (GLCA), parametric epistemic things (PET), presilience, and postponism. Finally, it provides a case study that shows how this assortment of contrivances, and AAA theory at large, can be used not just for theoretical musings, but to produce actual architectural schemes based on more precise data analyses than is typically the case in today’s built environment.A concluding discussion establishes that the use of more advanced and complex optimisation strategies is not just a possibility but a necessary obligation for an architecture, engineering, and construction (AEC) industry that – if the manufacturing of building materials are added to the construction and operation of buildings – is responsible for between 35% and 40% of both global final energy use and worldwide energy-related CO2 emissions. Claiming that our knowledge of materials, including the auxiliary loads that they carry (such as their global warming potential) can be used to design and engineer architectural assemblages capable of replacing energy-consuming with energy-producing buildings, it suggests that Le Corbusier’s famous dictum that buildings are ‘machines for living in’ should be replaced with the notion that all buildings are potential power plants for living in. Risks associated with the development of AAAs are discussed, and future studies proposed.
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| 3. |
- Larsson, Magnus, et al.
(författare)
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Novel Processes for Architectural Optimisation of Building Materials Performance: Introducing Material Phase Transitions and Generative Life Cycle Assessments
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Tidskriftsartikel (refereegranskat)abstract
- Conventional phase diagrams plot differences in properties (e.g. volume) of a medium generated by changes in external conditions (e.g. temperature and/or pressure). This paper discusses how the logic of such diagrams can be applied to produce a new type of surface plot, material phase transition (MPT) diagrams, that chart not the conditions for chemical equilibrium but the relative benefits of a particular material system given a set of predefined objectives and a virtual search space of design solutions. Such diagrams can form an integral part of parametric design processes that use ‘auxiliary loads’ (e.g. LCA values) as variables to generate design iterations. A Grasshopper user object is created and used to design a box beam that yields a set of auxiliary loads charts and MPT diagrams. The anatomy of MPT diagrams is described, and areas for future studies discussed.
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| 4. |
- Larsson, Magnus, et al.
(författare)
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Optimisation of timber structures based on weighted objectives
- 2017
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Ingår i: Proceedings of the 13th annual meeting of the Northern European Network for Wood Science and Engineering , September 28-29. ; , s. 79-84
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Contextual optimisation workspace (COW) is a digital design tool under developmentthat seeks to promote novel processes for the parametric design of architectural andengineering structures using multiple-objective optimisation (MOO) strategies based onevolutionary algorithms. Assembled within the Grasshopper (GH) graphical algorithmeditor, the tool allows for constructive analytical comparisons between often conflictingaspects of a design that have historically been assumed incomparable, with the resultingcompromises between objectives presented as iterations of a three-dimensionalgeometry with associated data. This increases the capability to make informeddecisions throughout the design process and to control the implementation of apotentially wide range of differing design objectives. This is useful in situations wherean extended design team (more than one stakeholder) is collaborating on anarchitectural project, which would include most real-life applications. In such a team, allagents have different preferred outcomes. The effort to manage their expectations andfulfil their respective agendas becomes the aim of the resulting architectural scheme.This paper explores how the COW tool could benefit from the addition of componentsthat simplify such decision-making processes, and showcases how such additions couldbe applied to the design of timber structures. Two new GH user objects were designedthat simplify an extended and weighted control of MOO-based design actions usingCOW, while providing a mechanism that guarantees designs are not considered if theydo not meet the minimal requirements set by the constraining frame conditions. Suchstakeholder-based MOO designs are shown to be a beneficial addition to the COWsystem. It is argued that a more comprehensive version of this first attempt to allowdiffering desires to be used as a weighted part of the design process is a promisingstrategy for the design of future timber structures.
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| 5. |
- Larsson, Magnus, et al.
(författare)
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Sliding Sidewinders: Early-Stage Design of an Anticipatory Adaptive Assemblage
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Tidskriftsartikel (refereegranskat)abstract
- This quantitative/qualitative evaluation of meta-heuristic design processes being implemented in a real-life architecture project introduces the theoretical concept of anticipatory adaptive assemblages (AAA) and reports on tactics that were used to reduce the ‘curse of dimensionality’ associated with the mechanisms that produce such assemblages. It describes strategies to adopt ‘presilient’ methods to constrain a model’s design space before any evolutionary solving occurs, leverage the advantage in fenestration performance presumed to arise from explorations of non-periodic tessellations of the plane, and use benchmark models to optimise some material aspects of wall sections. These tactics all support a materiality-based approach to designing architecture using genetic algorithms. The experiments were designed in an attempt to begin to close the knowledge gap between on the one hand the existing praxis of LCA-based analyses, on the other simulations that use material properties to directly inform geometries associated with particular combinations of (for instance) site, weather, and material data. The hypothesis is that AAA’s can become an effective framework for design-based adaptation to site conditions and mitigation of climate change. The objectives of the study are a) to implicitly and qualitatively describe the trials and tribulations a commercial adaptation of alternative design processes may cause, while b) explicitly and quantitatively report on the results of the experiments, and how they relate to AAAs. After an introduction of the AAA concept, three design experiments are described and their outcomes analysed, followed by a concluding discussion including suggestions for future studies.
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| 6. |
- Larsson, Magnus, et al.
(författare)
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Teleodynamic timber façades
- 2018
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Ingår i: Frontiers in Built Environment. - : Frontiers Media S.A.. - 2297-3362. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates ways in which weathering-related site conditions can be allowed to inform the design process in order to improve a building's geometry and performance. Providing a building design with the capacity to remember past experiences and anticipate future events can provide substantial gains to the architectural configuration and engineering of a timber façade. A new theory of architecture is outlined based on recent “teleodynamic” theories—a hypothesis about the way far-from-equilibrium systems interact and combine to produce emergent patterns. The proposed explanation considers nested levels of thermodynamic systems applied to an architectural context: “homeodynamic” operations that involve equilibration and dissipation of constraint combine to produce self-organising “morphodynamic” procedures that amplify and regularise site-specific constraining data streams. A teleodynamic design reconstitutes itself by combining morphodynamic processes so as to optimise its relationship to the past, present, and future. A novel teleodynamic design tool called Contextual Optimisation Workspace (COW) is assembled within the Grasshopper visual programming environment. The tool is used to carry out four experiments that combine to produce the teleodynamic design of an urban wooden façade, exemplifying an alternative framework for the design of wood-based structures. The first experiment investigates a variegated grid combining two distinct subdivision methods (an orthogonal grid and a Voronoi tessellation), transmuting one system into another. The second and third experiments focus on durability aspects of a wooden façade and devise strategies for how the effects of photochemical degradation and wetting due to driving rain might be minimised using the COW tool. The fourth experiment optimises the building for daylight based on an illuminance simulation. Using simulation and anticipation to add the advantages of site- and time-specific data streams as a design strategy can effectively suspend an algorithm-driven design iteration in time and space in order to allow it to be parametrically influenced by past or future events such as unique site and project conditions. The COW tool can be used to produce such teleodynamic designs.
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| 7. |
- Bjurhager, Ingela
(författare)
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Mechanical behaviour of hardwoods : effects from cellular and cell wall structures
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med den här avhandlingen var att undersöka mekaniska egenskaper hos olika arter av lövträd, och koppla egenskaperna till cell- och cellväggsstrukturen i materialet. Arterna som omfattades av undersökningen var Europeisk asp (Populus tremula), hybridasp (Populus tremula x Populus tremuloides) och ek (Quercus robur). Arterna inom familjen Populus, inklusive den snabbväxande hybridaspen, har på senare tid kommit att användas inom ett stort antal projekt inom genforskningen. Det har i sin tur ökat behovet av noggrannare bestämning av mekaniska egenskaper hos dessa arter. Ek har sedan tusentals år tillbaka varit ett populärt konstruktionsmaterial; något som har resulterat i ett stort antal arkeologiska ekfynd. Konservering av dessa inkluderar ofta dimensionsstabilisering med hjälp av polyetylen-glykol (PEG); en kemikalie som man vet påverkar de mekaniska egenskaperna. I vilken utstäckning detta sker är däremot inte helt klarlagt. Studien på euoropeisk asp och hybridasp inkluderade utveckling av en ny metod för provning av små juvenila prov i grönt tillstånd. Töjningsmätningar gjordes med hjälp av digital speckelfotografering (DSP). Axiell dragstyvhet och draghållfasthet var av speciellt intresse. Sämre mekaniska egenskaper hos hybridaspen korrelerade med medelvärden på densitet, som var lägre för hybriden än för den Europeiska aspen. Ek undersöktes i svällt tillstånd, där svällningen inducerades med hjälp av PEG (molekylvikt 600). Axiell dragstyvhet och draghållfasthet samt radiell tryckstyvhet och ytspänning undersöktes. Töjningsmätningar i axiell riktning gjordes med hjälp av videoextensiometer, medan töjning i radiell riktning gjordes med hjälp av DSP. Övrig karakterisering av materialet inkluderade scanning electron microscopy (SEM), röntgenmikrotomografi och wide angle X-ray scattering (WAXS) för bestämning av mikrofibrillvinkel. Axiell dragstyvhet och draghållfasthet påverkades bara marginellt av PEG-behandlingen. WAXS-mätningarna visade att mikrofibrillvinkeln i materialet var mycket liten. Därigenom blir de mekaniska egenskaperna i axiell riktning till stor del beroende av mikrofibrillerna, vilket samtidigt minimerar den mjukningseffekt som PEG-impregneringen har på cellväggsmatrisen. De mekaniska egenskaperna i radiell kompression påverkades däremot starkt negativt av impregneringen. Detta antogs bero på den försvagande och uppmjukande effekt som PEG:en har på de radiellt orienterade märgstrålarna i veden.
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| 8. |
- Bryne, Lars-Elof, et al.
(författare)
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Ageing of modified wood : Part 2: Determination of surface composition of acetylated, furfurylated, and thermally modified wood by XPS and ToF-SIMS
- 2010
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 64:3, s. 305-313
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of this work was to study the chemical composition of surfaces and ageing effects on acetylated pine (Pinus sylvestris), heat treated spruce (Picea abies), and furfurylated radiata pine (Pinus radiata) in comparison to unmodified wood. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were the instruments of choice. Observation with a low-vacuum scanning electron microscope (LV-SEM) complemented the study. The spectroscopic information was also linked to a parallel wettability study on matched wood samples by the Wilhelmy method. The results show that XPS and ToF-SIMS are two powerful tools that in combination give complementary information, both quantitative and qualitative, and are well suited for observation of the ageing process of different wood surfaces. The hydrophobization process as a result of migration of extractives during ageing was well quantified by the XPS measurements and the results correlated well with wetting results. Several specific hydrophobic substances could be identified by ToF-SIMS measurements.
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| 9. |
- Bryne, Lars-Elof, et al.
(författare)
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Ageing of modified wood : Part 1: Wetting properties of acetylated, furfurylated, and thermally modified
- 2010
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 64:3, s. 295-304
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of this work was to apply contact angle analysis to predict work of adhesion (W-a) between some modified wood materials and certain thermoplastics and adhesives. Wetting properties, i.e., contact angles, were measured by the Wilhelmy method on both freshly prepared and aged veneer samples of unmodified and acetylated Scots pine, furfurylated radiata pine, and heat treated Norway spruce. The sessile drop method was used to measure contact angles on a phenol resorcinol formaldehyde, an emulsion polymer isocyanate, and a one-component polyurethane adhesive. Contact angle data were also collected from the literature on polyethylene, polyvinyl chloride, polymethyl methacrylate, polystyrene, and Nylon 6. Contact angle analysis based on the Chang-Qin-Chen model was then applied to determine so-called acid-base interaction parameters and W-a between the wood samples and the selected thermoplastics and adhesives. Results show that the ageing process led to an increased hydrophobic character of unmodified, heat treated, and furfurylated wood samples. The freshly prepared acetylated wood samples had a pronounced hydrophobic character which remained approximately constant after ageing. The predicted W-a between the wood and the adhesives was considerably higher than that between the wood and the thermoplastics. Furthermore, the predicted W-a between the acetylated wood and both the thermoplastics and water was approximately unchanged when comparing the fresh and aged samples. In contrast, the ageing of all other wood samples resulted in a dramatic decrease of the wood-water W-a and a moderate decrease of the wood-thermoplastics W-a. The wood-adhesives W-a, however, was unchanged for the unmodified and furfurylated wood when comparing the fresh and aged samples and even increased for heat treated and acetylated wood samples.
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| 10. |
- Bryne, Lars Elof, et al.
(författare)
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UV-laser irradiated wood : Some aspects on micromorphology, wettability, surface composition and liquid permeability
- 2008
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Ingår i: Proceedings of the 4th meeting of the Nordic-Baltic network in wood material science and engineering (WSE). ; , s. 75-82
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Konferensbidrag (refereegranskat)abstract
- Many wood products used as building or construction materials involve a combination of the wood material with polymers, such as adhesives, coatings, preservatives and binders in composites. Combinations of wood and polymers in outdoor exposure, however, in general have poor long-term durability. A major cause of the unsatisfactory durability can be related to the high hygroscopicity of wood and the great difference in hygro-thermal properties between the components, resulting in wood-polymer de-bonding. In addition, mechanical processing (e.g. sawing, sanding and planning) of wood in general forms a weak boundary layer of loose and crushed wood cells in the surface which also may interfere with the wood-polymer bonding. The main objective of this work was to study ultra violet (EV), or excimer, laser irradiation on wood as a means to remove, by ablation, the outer deformed layer from a wood substrate. Effects of the UV-laser treatment on wetting and liquid permeability characteristics were studied by Wilhelmy plate experiments, and effects on the wood surface chemistry were studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The micromorphology of wood was studied by low vacuum-scanning electron microscopy (LV-SEM). The pre-treatment of wood substrates by UV-laser ablation resulted in a notable changes in surface micromorphology, liquid permeability, wettability and surface chemistry characteristics.
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| 11. |
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| 12. |
- Crocetti, Roberto, et al.
(författare)
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Multiple shear plane connections with timber based gusset plates
- 2021
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Ingår i: World Conference on Timber Engineering 2021, WCTE 2021. - : World Conference on Timber Engineering (WCTE).
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Konferensbidrag (refereegranskat)abstract
- This paper presents the results of an experimental study conducted on multiple-shear joints consisting of gusset plates made of either LVL or plywood connected to the timber members by means of full-threaded self-tapping screw. Both hardwood and softwood timber based gusset plates with different thickness and face grain orientations were investigated. The results show that this type of connection has an excellent structural performance, with not very dissimilar strength from that of comparable connections which makes use of slotted-in steel plates and dowels. It is believed, therefore, that the proposed solution can be a valid alternative to the more traditional timber connection with slotted-in steel plates and dowels.
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| 13. |
- Debertolis, Mattia, et al.
(författare)
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Investigation on mechanical connections with birch plywood gusset plates
- 2023
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Ingår i: 19th Annual Meeting of the Northern European Network for Wood Science and Engineering. - Ås, Norway : The Nordic Forest Research Cooperation Commitee. ; , s. 96-98
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Konferensbidrag (refereegranskat)abstract
- The construction industry is increasingly driven by sustainability concerns, prompting a search for alternative materials with a low environmental footprint, such as engineered wood products. Nowadays, connections of timber elements are still performed by the use of steel plates. However, steel plates can be replaced by plywood made of birch since it has superior mechanical properties compared to plywood made from softwood (Wang et al. 2021, 2022; Crocetti et al. 2021; Werner Åström, 2019). Besides, the capacity calculation for this connection according to the standards is conservative, meaning that the efficiency is low and the actual capacity could be much higher than the design value (Rossi et al. 2016). This research aims to enhance the knowledge and the design process of timber-to-timber connections with birch plywood (BP) plates.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Englund, F., et al.
(författare)
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Spectroscopic studies of surface chemical composition and wettability of modified wood
- 2009
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 4:1-2, s. 80-85
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in spectroscopic methods used in the surface science field may provide new valuable information about the surface chemical composition of engineering materials. Such methods, combined with wettability analyses, have been applied in the development of well-designed adhesives and coating systems for newly developed and commercially available modified wood materials. The main objective of this paper is to demonstrate and present some aspects on the application of two different state-of-the-art spectroscopic methods for surface chemical composition studies of a complex material such as modified wood. The methods are X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), the former generating more quantitative data and the latter more qualitative data. The spectroscopic data are also combined with wettability data obtained from contact angle measurements using the Wilhelmy method. Modified wood samples were prepared from pilot plant or commercially produced acetylated, furfurylated and thermally modified wood. Effects of wood surface ageing, i.e. the time after machining, on the surface chemical composition and wettability were also studied. Results clearly indicate a hydrophobization process due to ageing of the unmodified and certain modified wood, probably mainly related to a migration and reformation of extractives in the surface. The surface composition and wettability of acetylated wood was not appreciably affected by the ageing process. Such findings could be quantified by the XPS measurements, which is further discussed and related to the different wood modification routes. ToF- SIMS is a powerful tool and complementary to XPS for identification of, for example, specific hydrophobic substances in the wood surfaces. In addition, this method provides ion images, mapping the lateral distribution of selected secondary ions signals within an analysed wood surface area.
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| 25. |
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| 26. |
- Falk, Andreas, 1974-, et al.
(författare)
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Function and design of innovative bio-based products for the building sector
- 2016
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Ingår i: Structures and Architecture - Proceedings of the 3rd International Conference on Structures and Architecture, ICSA 2016. - : CRC Press/Balkema. - 9781138026513 ; , s. 93-101
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Konferensbidrag (refereegranskat)abstract
- This paper will present a study of preconditions for competitiveness in a resource saving society. Preconditions for material suppliers and industry versus requirements from legislation and consumers means a balance, which can be difficult to manage. The paper is aiming for an analysis of the preconditions for property modification, innovation and marketing of biobased materials and products, and the paper deals with strategies to release the architectural potential of bio-based construction.
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| 27. |
- Gardner, D. J., et al.
(författare)
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Editorial note
- 2006
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Ingår i: Journal of Adhesion Science and Technology. - : VSP. - 0169-4243 .- 1568-5616. ; 20:8, s. 723-723
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 28. |
- Inoue, Masafumi, et al.
(författare)
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Dimensional stabilization of compressed laminated veneer lumber by hot pressing in an airtight frame
- 2008
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 3:3-4, s. 119-125
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Tidskriftsartikel (refereegranskat)abstract
- Abstract The purpose of this study was to evaluate the dimensional stability and strength properties of compressed laminated veneer lumber (LVL) produced using a closed hot pressing system. LVL specimens were produced with varying number of veneers using either diphenylmethane diisocyanate (MDI) or a water-soluble phenol formaldehyde (PF) resin at varying temperatures (160?200°C), pressures (0.5?3 MPa) and hot-pressing times (2?16 min). Results show that the heating process decreases the recovery of compressive deformation in the veneers when subjected to cyclic moisture and heat conditions. Thickness swelling was approximately 5% after a drying, wetting and boiling cyclic test for LVL using the MDI resin and hot pressed at 200°C for 8 min. Modulus of elasticity and rupture increased for samples produced in both an open press and the closed press with an increase in the number of veneers and density, as did the absorbed energy in impact bending.
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| 29. |
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| 30. |
- Källbom, Susanna
(författare)
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Characterisation of thermally modified wood for use as component in biobased building materials
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The building sector shows growing interest in biobased building materials. Wood components, here defined as ground or milled wood, i.e. by-products (residuals/residues) from wood processing, such as sawdust or shavings, are valuable raw materials for new types of durable biocomposites suitable for outdoor building applications. An important research question related to such composites is how to characterise and enhance molecular interactions, i.e. adhesion properties, between wood and binder components. Another challenge is the hygroscopicity of the wood component, which can lead to dimensional changes and interfacial cracks during exposure to varying moisture conditions. Thermal modification of wood reduces its hygroscopicity, thereby, increasing its durability, e.g. its dimensional stability and resistance to biodeterioration. The hypothesis is that the use of thermally modified wood (TMW) components in biocomposites can enhance their durability properties and, at the same time, increase the value of residues from TMW processing. The main objective of this thesis is to study and analyse the surface and sorption properties of TMW components using inverse gas chromatography (IGC), dynamic vapour sorption (DVS), X-ray photoelectron spectroscopy (XPS), and the multicycle Wilhelmy plate method. The aim is to gain a better understanding of the surface and sorption characteristics of TMW components to enable the design of optimal adhesion properties and material combinations (compatibility) for use in biocomposites, especially suitable for outdoor and moist building material applications. Samples of TMW and unmodified wood (UW) components of Norway spruce (Picea abies Karst.) and Scots pine (Pinus sylvestris L.) heartwood were prepared and analysed with respect to surface energetics, hygroscopicity, liquid sorption and resulting swelling. The work also included analysis of surface chemical composition, as well as influences of extractives and moisture sorption history. The effect of using TMW components in a wood plastic composite (WPC) exposed to a series of soaking-drying cycles in water was studied with a focus on water sorption, swelling and micromorphological changes. The IGC analyses indicate that TMW components of spruce have a more heterogeneous surface energy character, i.e. a distinctly higher dispersive part of surface energy for low surface coverages, than do UW components. This is suggested to be due to the higher percentage of hydrophobic extractives present in TMW samples. Lewis acid-base analysis indicates that both UW and TMW components from spruce have a predominantly basic character and an enhanced basicity for the latter ones. Results show that both the hygroscopicity and water liquid uptake are lower for TMW than for UW samples. Unexpectedly, a significantly lower rate of water uptake was found for the extracted UW of pine heartwood than for non-extracted samples. In the former case, this is presumably due to contamination effects from water-soluble extractives, which increase capillary flow into wood voids, as proven by a decrease in water surface tension. Water uptake as well as swelling was significantly reduced for the WPCs with TMW and hot-water extracted UW components compared with the WPCs with UW components. This reduction also resulted in fewer wood component-polymer interfacial cracks in the WPCs with the modified wood components.
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| 31. |
- Källbom, Susanna, et al.
(författare)
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Effects of water soaking-drying cycles on thermally modified spruce wood-plastic composites
- 2020
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Ingår i: Wood and Fiber Science. - : SOC WOOD SCI TECHNOL. - 0735-6161. ; 52:1, s. 2-12
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Tidskriftsartikel (refereegranskat)abstract
- The overall aim of this work was to gain more insight on the potential of modified wood (TMW) components for use in wood-thermoplastic composites (WPCs). Laboratory-scale TMWPCs were produced, and the effects of severe water soaking-drying cycles on the samples were studied. Water sorption behavior and resulting dimensional and micromorphological changes were also studied, and the results were compared with those of unmodified wood-plastic composites (UWPCs) used as control. The TMW was prepared by cutting a spruce board into half and subjecting one-half to an atmosphere of superheated steam at atmospheric pressure with a peak temperature of 210 degrees C, with the other unmodified wood (UW) half as a control. The TMW and UW components were then prepared by a Wiley mill and thereafter sifted into smaller (mesh 0.20-0.40 mm) and larger (mesh 0.40-0.63 mm) size fractions. A portion of the wood components were also subjected to hydrothermal extraction (HE). Composite samples with these different wood components, polypropylene (PP) matrix, and maleated PP (MAPP) as coupling agent (50/48/2 wood/PP/MAPP ratio by weight) were then prepared by using a Brabender mixer followed by hot pressing. The matching micromorphology of the composites before and after the soaking-drying cycles was analyzed using a surface preparation technique based on ultraviolet-laser ablation combined with scanning electron microscopy. The results of the water absorption tests showed, as hypothesized, a significantly reduced water absorption and resulting thickness swelling at the end of a soaking cycle for the TMWPCs compared with the controls (UWPCs). The water absorption was reduced with about 50-70% for TMWPC and 60-75% for HE-TMWPC. The thickness swelling for TMWPCs was reduced with about 40-70% compared with the controls. Similarly, the WPCs with HE-UW components absorbed about 20-45% less moisture and showed a reduced thickness swelling of about 25-40% compared with the controls. These observations also were in agreement with the micromorphology analysis of the composites before and after the moisture cycling which showed a more pronounced wood-plastic interfacial cracking (de-bonding) as well as other microstructure changes in the controls compared with those prepared with TMW and HE-UW components. Based on these observations, it is suggested that these potential bio-based building materials show increased potential durability for applications in harsh outdoor environments, in particular TMWPCs with a well-defined and comparably small size fractions of TMW components.
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| 32. |
- Källbom, Susanna, et al.
(författare)
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Liquid sorption, swelling and surface energy properties of unmodified and thermally modified Scots pine heartwood after extraction
- 2018
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:3
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Tidskriftsartikel (refereegranskat)abstract
- The effect of extractives removal on liquid sorption, swelling and surface energy properties of unmodified wood (UW) and thermally modified Scots pine heartwood (hW) (TMW) was studied. The extraction was performed by a Soxtec procedure with a series of solvents and the results were observed by the multicycle Wilhelmy plate method, inverse gas chromatography (IGC) and Fourier transform infrared (FTIR) spectroscopy. A significantly lower rate of water uptake was found for the extracted UW, compared with the unextracted one. This is due to a contamination effect in the latter case from water-soluble extractives increasing the capillary flow into the wood voids, proven by the decreased water surface tension. The swelling in water increased after extraction 1.7 and 3 times in the cases of UW and TMW, respectively. The dispersive part of the surface energy was lower for the extracted TMW compared to the other sample groups, indicating an almost complete removal of the extractives. The FTIR spectra of the extracts showed the presence of phenolic compounds but also resin acids and aliphatic compounds.
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| 33. |
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| 34. |
- Källbom, Susanna, et al.
(författare)
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Sorption and surface energy properties of thermally modified spruce wood components
- 2018
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 50:3, s. 346-357
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work is to study the water vapor sorption and surface energy properties of thermally modified wood (TMW) components, ie wood processing residuals in the form of sawdust. The thermal modification was performed on spruce wood components using a steam-pressurized laboratoryscale reactor at two different temperature (T) and relative humidity (RH) conditions, T = 150 degrees C and RH = 100% (TMW150), and T = 180 degrees C and RH = 46% (TMW180). A dynamic vapor sorption (DVS) technique was used to determine water vapor sorption isotherms of the samples for three adsorption-desorption cycles at varying RH between 0% and 95%. Inverse gas chromatography (IGC) was used to study the surface energy properties of the samples, including dispersive and polar characteristics. The DVS results showed that the EMC was reduced by 30-50% for the TMW samples compared with control samples of unmodified wood (UW) components. A lower reduction was, however, observed for the second and third adsorption cycles compared with that of the first cycle. Ratios between EMC of TMW and that of UW samples were lower for the TMW180 compared with the TMW150 samples, and an overall decrease in such EMC ratios was observed at higher RH for both TMW samples. The IGC results showed that the dispersive contribution to the surface energy was higher at lower surface coverages, ie representing the higher energy sites, for the TMW compared with the UW samples. In addition, an analysis of the acid-base properties indicated a higher KB than KA number, ie a higher basic than acidic contribution to the surface energy, for all the samples. A higher KB number was also observed for the TMW compared with the UW samples, suggested to relate to the presence of ether bonds from increased lignin and/or extractives content at the surface. The KB was lower for TMW180 compared with TMW150, as a result of higher modification temperature of the first, leading to cleavage of these ether bonds.
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| 35. |
- Källbom, Susanna, 1988-
(författare)
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Surface characterisation of thermally modified spruce wood and influence of water vapour sorption
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today there is growing interest within the construction sector to increase the proportion of biobased building materials made from renewable resources. By-products or residuals from wood processing could in this case be valuable resources for manufacturing new types of biocomposites. An important research question related to wood-based biocomposites is how to characterise molecular interactions between the different components in the composite. The hygroscopic character of wood and its water sorption properties are also crucial. Thermal modification (or heat treatment) of wood results in a number of enhanced properties such as reduced hygroscopicity and improved dimensional stability as well as increased resistance to microbiological decay.In this thesis, surface characteristics of thermally modified wood components (often called wood fibres or particles) and influencing effects from moisture sorption have been analysed using a number of material characterisation techniques. The aim is to increase the understanding in how to design efficient material combinations for the use of such wood components in biocomposites. The specific objective was to study surface energy characteristics of thermally modified spruce (Picea abies Karst.) under influences of water vapour sorption. An effort was also made to establish a link between surface energy and surface chemical composition. The surface energy of both thermally modified and unmodified wood components were studied at different surface coverages using inverse gas chromatography (IGC), providing information about the heterogeneity of the surface energy. The water vapour sorption behaviour of the wood components was studied using the dynamic vapour sorption (DVS) method, and their surface chemical composition was studied by means of X-ray photoelectron spectroscopy (XPS). Additionally, the morphology of the wood components was studied with scanning electron microscopy (SEM).The IGC analysis indicated a more heterogeneous surface energy character of the thermally modified wood compared with the unmodified wood. An increase of the dispersive surface energy due to exposure to an increased relative humidity (RH) from 0% to 75% RH at 30 ˚C was also indicated for the modified samples. The DVS analysis indicated an increase in equilibrium moisture content (EMC) in adsorption due to the exposure to 75% RH. Furthermore, the XPS results indicated a decrease of extractable and a relative increase of non-extractable compounds due to the exposure, valid for both the modified and the unmodified wood. The property changes due to the increased RH condition and also due to the thermal modification are suggested to be related to alterations in the amount of accessible hydroxyl groups in the wood surface. Recommendations for future work and implications of the results could be related to knowledge-based tailoring of new compatible and durable material combinations, for example when using thermally modified wood components in new types of biocomposites for outdoor applications.
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| 36. |
- Källbom, Susanna, et al.
(författare)
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Surface chemical analysis and water vapour sorpion of thermally modified wood exposed to increased relative humidity
- 2015
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Ingår i: The Eighth European Conference on Wood Modification (ECWM8) 2015.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The increased interest in environmentally friendly building materials is accompanied with an increased need for research on thermally modified wood. Products made from recycling or reusing of thermally modified residuals will have advantages in terms of environmental aspects. Surface characteristics of thermally modified wood play an important role for the development of applications involving bonding processes, for example when using thermally modified wood residuals in biocomposites. Surface chemistry characteristics are important in developing such materials. A technique used for surface chemical analysis of the outermost surface is X‑ray photoelectron spectroscopy (XPS). Some surface chemical analyses of wood and modified wood can be found in Nzokou and Kamdem (2005), Inari et al. (2006), Bryne et al. (2010), Johansson et al. (2012), Rautkari et al. (2012). Furthermore, the influence of water and moisture has crucial effect on the properties of wood and wood products. Water vapour sorption properties of hygroscopic materials can be studied using a dynamic vapour sorption (DVS) instrument. Previous studies on thermally modified wood exposed to several sorption cycles using DVS have shown an increase in hysteresis during the first cycle, compared with unmodified wood (Hill et al., 2012). However, during the second and the third sorption cycle a reduction in sorption hysteresis was observed. The objective of this work was to study the surface chemical composition and water vapour sorption properties of thermally modified wood. In particular, an effort was made to study any influence on such properties due to a previous exposure to a high relative humidity (RH). Interpretations of the results indicate a decrease of extractable or volatile organic components and a relative increase of non-extractable components, for the high humidity-exposed samples. This could be due to remaining extractives migrating towards or redistribution at the wood surface layer as a result of moisture diffusion. The DVS results show that the thermally modified wood samples that had been exposed to the high relative humidity condition revealed a slight decrease of the hysteresis of the sorption isotherms. The opposite trend was furthermore seen for the unmodified wood.
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| 37. |
- Källbom, Susanna, 1988-, et al.
(författare)
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Surface energy characteristics of refined fibres at different pressures
- 2014
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Ingår i: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014). ; , s. 134-138
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Wood fibres were produced on the pilot scale refiner at the BioComposites Centre, Bangor University, from a commercially sourced mix of chipped wood. The fibres were produced at refiner pressure 4, 6, 8 and 10 bar and dried in the associated flash drier. Surface energy characterization of the refined fibres was performed using inverse gas chromatography (IGC). The dispersive part of the total surface energy was analysed for duplicates of fibre samples at the four different refiner pressures. Non-polar alkane probes were used for the dispersive surface energy analysis at different surface coverage. Results indicate that the processing pressure has an effect of the dispersive surface energy and IGC analysis could be developed as a tool both for process development and process control in refining fibres.
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| 38. |
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| 39. |
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| 40. |
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| 41. |
- Källbom, Susanna, 1988-, et al.
(författare)
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Surface energy characterization of thermally modified spruce using inverse gas chromatography under cyclic humidity conditions
- 2015
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Ingår i: Wood and Fiber Science. - : SOC WOOD SCI TECHNOL. - 0735-6161. ; 47:4, s. 410-420
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Tidskriftsartikel (refereegranskat)abstract
- The surface energy of unmodified and thermally modified spruce wood components was researched at dry and moist conditions using inverse gas chromatography. The results indicate a more pronounced heterogeneous nature of the thermally modified wood surfaces in terms of the dispersive (nonpolar) component of the surface energy, compared with that of the unmodified wood surfaces. The dispersive component of the surface energy of the thermally modified wood ranged between 44 and 38 mJ/m(2) corresponding to an increase in surface coverage from a low level and up to about 10%. Suggested explanations for the more distinct heterogeneity of the thermally modified wood sample are related to chemical changes of the wood substance which seem to result in certain micromorphological features observed by scanning electron microscopy as alternated fracture surfaces created in the grinding process; and also possible changes or redistribution of the wood extractives. An increase of the MC, representing a change from a dry condition of approximately 0% RH to ca 75% RH, of both the unmodified and thermally modified samples seemed to have a marginal influence on the dispersive component of the surface energy. Possible implications of the results in this study can be found in the tailoring of new compatible and durable material combinations, for example, when using thermally modified wood residuals as a component in new types of biocomposites.
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| 42. |
- Källbom, Susanna, 1988-, et al.
(författare)
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Surface energy characterization of thermally modified wood particles exposed to humidity cycling using inverse gas chromatography
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this work was to study surface energetics of thermally modified wood particles exposed to dry-humid cycling. This information can give insight in the adhesion properties between the modified wood and composite matrices, adhesives or coatings. The surface energy characterization as well as the dry-humid cycling was performed using inverse gas chromatography (IGC). Duplicates of thermally modified and unmodified spruce particles with size 0-0.125 mm were investigated and conditioned in dry-humid cycles at 0-75 % RH and 0‑25 % RH. The BET specific surface area as well as the dispersive surface energy heterogeneity (or distribution) at different surface coverage was determined. The results showed similar trends for the different cycles in the dry and humid states, respectively. The difference in dispersive surface energy distribution between the dry and humid state was more pronounced at the lower surface coverage.
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| 43. |
- Källbom, Susanna, et al.
(författare)
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Surface energy characterization of thermally modified wood using inverse gas chromatography
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this work is to characterize surface energetics of thermally modified wood. Such information may be useful for a better understanding and predictions of adhesion properties between the modified wood and other material systems, e.g. coatings, adhesives or matrices in composites. Inverse gas chromatography (IGC) was used to study the surface energy characteristics of thermally modified spruce in particle form. Two different wood component samples were prepared, one with a larger and one with a smaller particle size distribution. Measurements of BET specific surface area and dispersive surface energy distribution of the particle samples are presented. Results indicate that a ground wood component of a finer size distribution of thermally modified wood is less energetically heterogeneous compared with a component with a larger size distribution.
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| 44. |
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| 45. |
- Källbom, Susanna, 1988-, et al.
(författare)
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The influence of log soaking temperature and thermal modification on the properties of birch veneers
- 2016
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Ingår i: IRG Annual Meeting. - : IRG Documents.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.
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| 46. |
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| 47. |
- Källbom, Susanna, 1988-, et al.
(författare)
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Water vapour sorption characteristics and surface chemical composition of thermally modified spruce (Picea abies karst)
- 2016
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Ingår i: International Wood Products Journal. - : Taylor & Francis. - 2042-6445 .- 2042-6453. ; 7:3, s. 116-123
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to study the hygroscopicity and surface chemical composition of thermally modified (TM) spruce. An effort was also made to study if those features were influenced by a previous exposure to a significant increase in relative humidity (RH). TM and unmodified Norway spruce (Picea abies Karst) samples, both in solid and ground form, were prepared. Water vapour sorption characteristics of the ground samples were obtained by measuring sorption isotherms using a dynamic vapour sorption (DVS). The surface chemical composition of the solid samples, both acetone extracted and non-extracted, were analysed using X-ray photoelectron spectroscopy (XPS). The DVS analysis indicated that the TM wood exposed to the 75% RH revealed a decrease in isotherm hysteresis. The XPS analysis indicated a decrease of acetone extractable or volatile organic components and a relative increase of non-extractable components for the samples exposed to the increased RH condition.
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| 48. |
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| 49. |
- Källbom, Susanna, et al.
(författare)
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Wood-plastic composites made from thermally modified spruce wood components and effects of exposure to water-soaking-drying cycles
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The over-all aim of this work is to gain more insight on the potential to use thermally modified wood (TMW) components in wood-thermoplastic composites (WPCs), ie a new type of biobased building material, here defined as TMWPCs, assumed to have significantly increased moisture resistance and durability related to conventional WPCs. The specific objective was to prepare lab-scale TMWPCs and WPC controls with unmodified wood (UW), and to expose these samples to a series of severe water-soaking-drying cycles to study the effects on the water sorption behavior and resulting dimensional and micromorphology changes. TMW was prepared by thermal modification of a spruce board in an atmosphere of superheated steam at atmospheric pressure with a peak temperature of 210°C (also matched with an UW board as control). TMW and UW components were then prepared by a Wiley mill and thereafter sifted into a smaller (0.20-0.40 mm) and a larger (0.40-0.63 mm) size fraction. A portion of the wood components were also hot-water extracted (HE) with liquid hot-water. Composite samples with these different wood components, polypropylene (PP) matrix, and maleated PP (MAPP) as coupling agent (50/48/2 wood/PP/MAPP ratio) were then prepared by using a Brabender mixer followed by hot-pressing. The matching micromorphology of the composites before and after the soaking-drying cycles was analyzed using a surface preparation technique based on UV-laser ablation combined with scanning electron microscopy (SEM). An effort was also made to study the wood-thermoplastic interfacial behavior in the composites by dynamic mechanical analysis (DMA). The results of the water absorption tests showed, as hypothesized, a significantly reduced water absorption and resulting thickness swelling for the TMWPCs compared with the controls. Similarly, the WPCs with HE-UW components showed a significant reduction in water absorption and thickness swelling compared with the controls. In contrast, the samples with HE-TMW components resulted in only minor moisture property changes. These observations were also in agreement with the micromorphology analysis of the composites before and after the moisture cycling which showed a more pronounced wood-plastic interfacial cracking (de-bonding) as well as other microstructure changes in the controls compared with those prepared with TMW and HE-UW components. The DMA indicated better dispersion and increased interfacial interaction for the WPCs with UW components with the smaller size fraction compared with the larger size fraction. The loss modulus and storage modulus were overall reduced for samples with HE and TMW components compared with those with UW components. Based on these observations it is suggested that a potential biobased building material with increased durability for applications in harsh outdoor environments may be tailored as a TMWPC with a well-defined and comparably small size fractions of TMW components.
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| 50. |
- Laine, Kristiina, et al.
(författare)
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Acetylation and densification of wood
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this study was to explore the possibility to surface densify acetylated solid wood. The aim of surface densification is to improve mechanical properties, such as hardness, at the very surface of wood where the property improvements are mostly needed (e.g. in flooring and decking). However, when subjected to moisture, surface densified wood may swell back almost to the original dimensions. Therefore, acetylated and non-acetylated wood was surface densified in order to investigate whether the dimensional stability of densified wood may be improved by pre-acetylation. Surface densification was performed by compressing the acetylated radiate pine samples between metal plates with only one side heated (150°C) in order to target the deformation to one surface only. The original thickness of the samples was 20 mm and the target thickness 18 mm which was controlled by metal stops. The recovery of the deformation (set-recovery) was measured by soaking the samples in water and measuring the oven-dry thickness before and after soaking in repeated cycles. It was found that acetylated wood may be surface densified and indeed the set-recovery of the pre-acetylated wood was significantly lower (17.4 %) compared to non-acetylated wood (72.8 %). Further studies in adjusting the process parameters might lead to even higher reduction in set-recovery.
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