Lauri Rautkari

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One-sided surface charring of beech wood

Petr Čermák, Aleš Dejmal, Zuzana Paschová, Maija Kymäläinen, more

Journal of Materials Science > 2019 > 54 > 13 > 9497-9506

One-sided surface charring of beech wood (Fagus sylvatica L.) was analyzed. Specimens were charred on one surface using contact heating system with a hot plate, at a temperature of 220 °C and atmospheric pressure for 15 or 40 min. Surface charring was applied on the radial or tangential surface. Spectrophotometric chemical analysis was carried out to determine the total amount of soluble carbohydrates...

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Small‐angle scattering model for efficient characterization of wood nanostructure and moisture behaviour

Paavo A. Penttilä, Lauri Rautkari, Monika Österberg, Ralf Schweins

Journal of Applied Crystallography > 52 > 2 > 369 - 377

Small‐angle scattering methods allow an efficient characterization of the hierarchical structure of wood and other cellulosic materials. However, their full utilization would require an analytical model to fit the experimental data. This contribution presents a small‐angle scattering model tailored to the analysis of wood samples. The model is based on infinitely long cylinders packed in a hexagonal...

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Determining the degree of heat treatment of wood by light polarization technique

Hariyadi Soetedjo, Ilpo Niskanen, Lauri Rautkari, Michael Altgen, more

European Journal of Wood and Wood Products > 2018 > 76 > 4 > 1359-1362

Thermal modification of wood enables the use of non-durable wood species in exterior applications, but quality control methods are required to monitor the product variability. This study tests the potential of a light polarization technique where visible light (400–500 nm) is directed through a linear polarizer to the surface of thermally modified wood to measure the reflectance. Besides an effect...

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The effect of de- and re-polymerization during heat-treatment on the mechanical behavior of Scots pine sapwood under quasi-static load

Michael Altgen, Tuuli Uimonen, Lauri Rautkari

Polymer Degradation and Stability > 2018 > 147 > C > 197-205

Loss in strength and ductility is a major drawback for the heat-treatment of solid wood. Previous studies focused mainly on the de-polymerization of cell wall constituents as a cause and the importance of the preferential removal of hemicelluloses. This study tested the hypothesis that the mechanical behavior of wood is additionally affected by re-polymerization reactions within the cell wall matrix...

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Experimental techniques for characterising water in wood covering the range from dry to fully water-saturated

Emil Engelund Thybring, Maija Kymäläinen, Lauri Rautkari

Wood Science and Technology > 2018 > 52 > 2 > 297-329

Water plays a central role in wood research, since it affects all material properties relevant to the performance of wood materials. Therefore, experimental techniques for characterising water within wood are an essential part of nearly all scientific investigations of wood materials. This review focuses on selected experimental techniques that can give deeper insights into various aspects of water...

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Cellular level distributions of Scots pine heartwood and knot heartwood extractives revealed by Raman spectroscopy imaging

Tiina Belt, Tobias Keplinger, Tuomas Hänninen, Lauri Rautkari

Industrial Crops and Products > 2017 > 108 > C > 327-335

Wood extractives are biologically active secondary metabolites that help protect wood and wood products from decay and other forms of biological attack. Despite the influence of distribution on their ability to protect wood, very few studies have investigated the distributions of extractives on a cellular level. In this paper, the distributions of extractives were studied in Scots pine (Pinus sylvestris...

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Changes in the hygroscopic behavior of cellulose due to variations in relative humidity

Ville A. Lovikka, Lauri Rautkari, Thaddeus C. Maloney

Cellulose > 2018 > 25 > 1 > 87-104

Details on how cellulosic surfaces change under changing moisture are incomplete and even existing results are occasionally neglected. Unlike sometimes reported, water adsorption is unsuitable for surface area measurements. However, water can be utilized for assessing surface dynamics. Hygroscopic changes of pulp and bacterial cellulose were studied by dehydrating the samples in a low polarity solvent...

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Chemical, water vapour sorption and ultrastructural analysis of Scots pine wood thermally modified in high-pressure reactor under saturated steam

Maija Kymäläinen, Selim Ben Mlouka, Tiina Belt, Vivian Merk, more

Journal of Materials Science > 2018 > 53 > 4 > 3027-3037

Thermal modification of wood results in improved dimensional stability and increases the end-use possibilities of wood. Modification under saturated steam is reported to result in higher performance when compared to more traditional thermal modification methods. This study analyses the chemical and ultrastructural changes, as well as water vapour sorption properties of Scots pine modified thermally...

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The influence of extractives on the sorption characteristics of Scots pine (Pinus sylvestris L.)

Katja Vahtikari, Lauri Rautkari, Tuula Noponen, Kristiina Lillqvist (née Laine), more

Journal of Materials Science > 2017 > 52 > 18 > 10840- 10852

The sorption behaviour of extracted and un-extracted Scots pine (Pinus sylvestris L.) heartwood was analysed using dynamic vapour sorption apparatus. In addition to the sorption isotherm and hysteresis, the moisture increments and decrements were determined as well as the rate of sorption. Parallel exponential kinetics model was used for further analysis. The effect of cyclic humidity loading on the...

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Surface modification of birch veneer by peroxide bleaching

Akio Yamamoto, Anti Rohumaa, Mark Hughes, Tapani Vuorinen, more

Wood Science and Technology > 2017 > 51 > 1 > 85-95

This study examined effects of surface modification with hydrogen peroxide (H₂O₂) on adhesive bond performance in birch veneer bonded with phenol–formaldehyde resin. The veneer was treated with 5% of H₂O₂ at 80 °C in the presence of alkali with the objective of improving adhesive bond performance and reducing the resin demand. The effects of the surface modification were determined by surface color...

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Surface densification of acetylated wood

Kristiina Laine, Kristoffer Segerholm, Magnus Wålinder, Lauri Rautkari, more

Holz als Roh- und Werkstoff > 2016 > 74 > 6 > 829-835

The mechanical properties of wood can be improved by compressing its porous structure between heated metal plates. By adjusting the process parameters it is possible to target the densification only in the surface region of wood where the property improvements are mostly needed in applications, such as flooring. The compressed form is, however, sensitive to moisture and will recover to some extent...

article

Influence of temperature of thermal treatment on surface densification of spruce

Mirko Kariz, Manja Kitek Kuzman, Milan Sernek, Mark Hughes, more

Holz als Roh- und Werkstoff > 2017 > 75 > 1 > 113-123

Spruce (Picea abies L. Karst) wood lamellae, thermally treated at 170, 190, 210 and 230 °C were surface densified by compression at a temperature of 150 °C to three degrees of compression. Immediate springback, set recovery, mechanical properties in 3-point flexure, Brinell hardness and density profiles measurements were used to determine the effect of thermal treatment on the properties of surface...

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Role of various nano-particles in prevention of fungal decay, mold growth and termite attack in wood, and their effect on weathering properties and water repellency

Evren Terzi, S. Nami Kartal, Nural Yılgör, Lauri Rautkari, more

International Biodeterioration & Biodegradation > 2016 > 107 > C > 77-87

The resistance of Scots pine wood vacuum-treated with nano-particles of ZnO, B₂O₃, CuO, TiO₂, CeO₂, and SnO₂ against decay, mold fungi and subterranean termites was evaluated. Weathering and water absorption properties were also studied. Nano-ZnO only was resistant against leaching, while the other compounds leached out from wood specimens at more than 60% release rates. Mold growth in wood specimens...

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Wood densification and thermal modification: hardness, set-recovery and micromorphology

Kristiina Laine, Kristoffer Segerholm, Magnus Wålinder, Lauri Rautkari, more

Wood Science and Technology > 2016 > 50 > 5 > 883-894

The density of wood can be increased by compressing the porous structure under suitable moisture and temperature conditions. One aim of such densification is to improve surface hardness, and therefore, densified wood might be particularly suitable for flooring products. After compression, however, the deformed wood material is sensitive to moisture, and in this case, recovered up to 60 % of the deformation...

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The effect of wetting cycles on moisture behaviour of thermally modified Scots pine (Pinus sylvestris L.) wood

Petr Čermák, Katja Vahtikari, Lauri Rautkari, Kristiina Laine, more

Journal of Materials Science > 2016 > 51 > 3 > 1504-1511

The moisture behaviour of thermally modified Scots pine (Pinus sylvestris L.) exposed to cyclic conditions was analysed. Specimens of dimensions 15 × 15 × 5 mm³ were thermally modified at 180 °C (TM₁) and 220 °C (TM₂) using atmospheric pressure and superheated steam. Radial, tangential, volumetric swelling and anti-swelling efficiency (ASE) were calculated during six consecutive drying–soaking cycles...

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Erratum to: Sorption behaviour of torrefied wood and charcoal determined by dynamic vapour sorption

Maija Kymäläinen, Lauri Rautkari, Callum A. S. Hill

Journal of Materials Science > 2016 > 51 > 2 > 1161-1161

article

Sorption behaviour of torrefied wood and charcoal determined by dynamic vapour sorption

Maija Kymäläinen, Lauri Rautkari, Callum A. S. Hill

Journal of Materials Science > 2015 > 50 > 23 > 7673-7680

The most important variable of biomass-based fuels is moisture, because it affects the entire logistic chain by creating problems related to transport, handling, storage, and combustion. Recently, there has been a growing interest in thermal pre-treatment of biomass-based fuels by torrefaction. Torrefaction is intended to overcome the moisture-related problems by significantly reducing hygroscopicity...

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Simultaneous drying and densification of silver birch (Betula pendula L.) veneers: analysis of morphology, thickness swelling, and density profile

Toni Antikainen, Olli Paajanen, Lauri Rautkari, Andreja Kutnar, more

Wood Science and Technology > 2014 > 48 > 2 > 325-336

In this study, birch (Betula pendula L.) veneers were simultaneously densified and dried using a contact drying method at pressures of 1.5 and 3 MPa at 130 °C and compared with veneer dried in a laboratory-scale convective type dryer. Compression rate, thickness swelling, and the density profiles of the veneers were investigated. Furthermore, the microstructure of densified veneers was studied by...

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Mechanical and physical properties of thermally modified Scots pine wood in high pressure reactor under saturated steam at 120, 150 and 180 °C

Lauri Rautkari, Juhani Honkanen, Callum A. S. Hill, Daniel Ridley-Ellis, more

Holz als Roh- und Werkstoff > 2014 > 72 > 1 > 33-41

Scots pine sapwood and heartwood were thermally modified under saturated steam at 120, 150 and 180 °C in a high pressure reactor. Mechanical properties such as dynamic and static modulus of elasticity (MOE), static modulus of rupture (MOR), Brinell hardness and impact toughness were evaluated. The static MOE for sapwood did not decrease substantially (approximately 1 %), not even with a high mass...

article

Accessibility of hydroxyl groups in birch kraft pulps quantified by deuterium exchange in D₂O vapor

Raili Pönni, Lauri Rautkari, Callum A. S. Hill, Tapani Vuorinen

Cellulose > 2014 > 21 > 3 > 1217-1226

Deuterium exchange in a deuterium oxide (D₂O) atmosphere (95 % relative humidity), quantified by a dynamic vapor sorption (DVS) apparatus, was applied for assessing the accessibility of hydroxyl groups in birch kraft pulps. Achieving the maximum deuteration level exhibited slower kinetics than was earlier reported for experiments with ground wood and bacterial cellulose. The deuterium exchange process...

INFONA - science communication portal

Search results for: Lauri Rautkari

One-sided surface charring of beech wood

Small‐angle scattering model for efficient characterization of wood nanostructure and moisture behaviour

Determining the degree of heat treatment of wood by light polarization technique

The effect of de- and re-polymerization during heat-treatment on the mechanical behavior of Scots pine sapwood under quasi-static load

Experimental techniques for characterising water in wood covering the range from dry to fully water-saturated

Cellular level distributions of Scots pine heartwood and knot heartwood extractives revealed by Raman spectroscopy imaging

Changes in the hygroscopic behavior of cellulose due to variations in relative humidity

Chemical, water vapour sorption and ultrastructural analysis of Scots pine wood thermally modified in high-pressure reactor under saturated steam

The influence of extractives on the sorption characteristics of Scots pine (Pinus sylvestris L.)

Surface modification of birch veneer by peroxide bleaching

Surface densification of acetylated wood

Influence of temperature of thermal treatment on surface densification of spruce

Role of various nano-particles in prevention of fungal decay, mold growth and termite attack in wood, and their effect on weathering properties and water repellency

Wood densification and thermal modification: hardness, set-recovery and micromorphology

The effect of wetting cycles on moisture behaviour of thermally modified Scots pine (Pinus sylvestris L.) wood

Erratum to: Sorption behaviour of torrefied wood and charcoal determined by dynamic vapour sorption

Sorption behaviour of torrefied wood and charcoal determined by dynamic vapour sorption

Simultaneous drying and densification of silver birch (Betula pendula L.) veneers: analysis of morphology, thickness swelling, and density profile

Mechanical and physical properties of thermally modified Scots pine wood in high pressure reactor under saturated steam at 120, 150 and 180 °C

Accessibility of hydroxyl groups in birch kraft pulps quantified by deuterium exchange in D₂O vapor

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