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Thermally modified (TM) wood production has significantly increased in the last decade. The trend for TM wood residues should be similar – rapidly increasing, which has prompted this research on the possible efficient uses of these residues, such as sawdust. One of the possibilities could be the production of wood plastic composites (WPCs). In this work, three different hydrothermal modification regimes were used to modify birch boards. Modified and unmodified birch boards were milled to obtain sawdust. WPCs were made with a two-roll mill, and they consisted of 50 wt-% wood fibres + 50 wt-% polypropylene. Melt flow index (MFI), flexural properties, impact strength, microhardness water absorption and dimensional stability were tested. WPCs with TM wood showed improvement in flexural properties, MFI and other properties, however there was a decrease in impact strength. Scanning electron microscopy pictures of impact strength samples fracture surfaces were taken. [ABSTRACT FROM AUTHOR]

This paper presents the European initiatives, strategies, and directives that must be considered in future development of thermally modified timber and when optimising the existing, commercialised processes and discusses the next steps in developing thermally modified timber needed to meet the requirements of the European low carbon economy. The standards for assessment of environmental impacts of processes and products with the focus on Environmental Product Declarations (EPDs) for materials used in the built environment are presented and followed by discussion about the need to consider the environmental impacts on sustainably aspects of thermally modified timber. This includes: determination of environmental impacts of processing and resulting products; design of processes and products towards minimal environmental impacts; and acquisition of EPDs and of Product Category Rules (PCR) for products of thermally modified timber. [ABSTRACT FROM AUTHOR]

Oligomers of lactic and glycolic acid (OLA, OGA) and poly(butylene succinate/adipate) (OBS, OBA) were impregnated and heated into wood for dimensional stabilisation. These bio-polyesters variously provide bulking and lumen filling treatments. Solvent extraction of treated wood showed that ca. 50% of the polymer remains in wood with in situ polymerisation evidenced by GPC. OGA readily penetrates the wood cell wall, which occurred only on heating OLA, whereas OBS/OBA was lumen filling with any cell wall penetration only evident after water soaking. Stability of OLA/OGA treated wood was improved, but did not withstand extended leaching, whereas OBS/OBA treated wood presented higher stability once leached. Bending resistance was influenced by OLA/OGA treatments, but original MOE values were recovered after leaching. Overall, the results show the bio-polyester treatment can confer specific properties of the modified wood to suit selected end use applications. [ABSTRACT FROM AUTHOR]

A large number of different heating technologies has been put into use for industrial scale thermal modification of wood. A useful classification of these processes is by the level of water vapour pressure, which ranges from vacuum to high saturated steam pressures. Only high water vapour pressure systems can maintain a finite moisture content during the heat treatment, but little is known about the water vapour pressure dependence of the thermal modification chemistry and the resulting modified wood properties. It is concluded from our analysis that the thermal wood reaction chemistry at the molecular functional group level is quite independent of the process and wood species. Wood properties that are strongly determined by wood chemical composition, such as the fungal durability and the equilibrium moisture content (EMC), can hence be equally achieved by all processes and for all wood species. This finding cannot be transferred to every other thermally modified wood property. [ABSTRACT FROM AUTHOR]

The work presented in this paper reports on the water sorption properties of thermally modified wood, densified wood and wood modified using a combination of the two methods. The paper presents new findings concerning the sorption isotherms and sorption kinetics behaviour. The sorption kinetics is analysed in terms of the parallel exponential kinetics (PEK) model which has recently been introduced to the wood science community as a better alternative to the often used Fickian models, at least where cell wall sorption behaviour is considered. The PEK model comprises two exponential sorption kinetic terms which are termed fast and slow sorption processes. The PEK model is then interpreted by using a relaxation-limited kinetics model consisting of two series-coupled Kelvin-Voigt elements. [ABSTRACT FROM AUTHOR]

A study was carried out to investigate the effect of thermal treatment on biological resistance of Populus tremuloides wood against four decay fungi, including T. versicolor, P. placenta, G. trabeum and C. puteana. The weight loss data showed that degradation of untreated wood by the white rot fungus T. versicolor resulted in higher weight loss (571%) compared to those by brown rot fungi G. trabeum (21•9%), P. placenta (36•7%) and C. puteana (7 1%). When this species was heat treated at 220°C, the weight loss was reduced to <10%. Increasing temperature and the holding time appeared to affect the resistance against I versicolor, P. placenta and G. trabeum attacks, but the effect on the resistance against C. puteana was not significant. The humidity during thermal modification affected the degradation of wood against I versicolor attack, but it did not have a significant effect on the other fungi. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented which introduces several articles within the issue on topics including insight on the mode of action of brown rot decay of modified wood based on DNA and gene expression studies, steps in developing thermally modified timber, and modification of wood with biopolyesters.

An introduction to the journal is presented which features several articles from the Seventh European Conference on Wood Modification on topics including thermo-hydromechanical wood behaviour and processing and performance of bio-based building materials.