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Furfurylated wood has been used widely for exterior purposes due to its superior dimensional stability and biological durability, though its fire resistance is not enhanced. Here, Scots pine (Pinus sylvestris L.) sapwood was impregnated with a hygroscopic fire-retardant guanyl-urea phosphate (GUP) and furfuryl alcohol (FA) by a vacuum-pressure impregnation followed by curing in elevated temperature. The water-resistance of such treated material was evaluated according to European standard EN 84. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) revealed the penetration of GUP into the cell wall. The hydrophobic FA polymerised in-situ within the wood structure, and this enhanced the water-resistance of GUP. Fourier-transform infrared spectroscopy (FTIR) showed that the chemical functionalities changed such as formation of methylene bridges attributed to the polymerised FA and ketone groups attributed to GUP. Thermal gravimetric analysis (TGA) showed that GUP enhanced thermal stability at elevated temperature by promoting char formation. Fire stability test examined by limiting oxygen index (LOI) showed the improvement of fire-retardancy by the incorporation of GUP. Mechanical properties examined by Brinell hardness and three-point bending test indicated that GUP has a low impact on the properties of surface hardness, modulus of elasticity (MOE) and modulus of rupture (MOR) of the furfurylated wood. The work suggests that GUP/FA treatment has the prospective to impart substantial fire-retardancy to the furfurylated wood with small reduction in other properties, thus increasing the potential for exterior applications.

Maleic anhydride (MA) is a cyclic anhydride capable of forming an ester bond with wood constituents, providing enhanced dimensional stability and fungal resistance of wood. However, the weight gain through treatment was lost during wet-dry cycle, which indicates that the ester bonds in maleated wood is susceptible to hydrolysis. This study focuses on improving the stability of the maleated product through the use of sodium hypophosphite. Studies have shown the combined treatment resulted in improved anti-swelling efficiency (ASE), lower weight loss and smaller saturated volumes than untreated or specimens treated with maleic anhydride along. In order to better understand the relationship between the modified wood and water, low-field nuclear magnetic resonance (LFNMR) spectroscopy was used to determine the influence of moisture in wood. The modification process resulted in a weak wood–water interaction using LFNMR, suggesting an increased T2 relaxation time of capillary water. However, the weak wood–water interaction did not seem to be related to the accessible hydroxyl groups because the modification reaction resulted in a similar number of hydroxyl groups as present in unmodified wood. This finding would appear to agree with the concept of MA modification resulting in the “ring opening” of the anhydride, creating a carboxylic acid group for each hydroxyl group modified within the wood. Funder: Northern European network for wood science and engineering (WSE); Advanced research supporting the forestry and wood-processing sector’s adaptation to global change and the 4th industrial revolution, OP RDE, (CZ.02.1.01/0.0/0.0/16_019/0000803)

Guanyl-urea phosphate (GUP) was introduced into furfurylated wood in order to improve fire retardancy. Modified wood was produced via vacuum-pressure impregnation of the GUP–furfuryl alcohol (FA) aqueous solution, which was then polymerized at elevated temperature. The water leaching resistance of the treated wood was tested according to European standard EN 84, while the leached water was analyzed using ultra-performance liquid chromatography (UPLC) and inductively coupled plasma–sector field mass spectrometry (ICP-SFMS). This new type of furfurylated wood was further characterized in the laboratory by evaluating its morphology and elemental composition using optical microscopy and electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDX). The chemical functionality was detected using infrared spectroscopy (FTIR), and the fire resistance was tested using cone calorimetry. The dimensional stability was evaluated in wet–dry soaking cycle tests, along with the mechanical properties, such as the Brinell hardness and bending strength. The fire retardancy of the modified furfurylated wood indicated that the flammability of wood can be depressed to some extent by introducing GUP. This was reflected in an observed reduction in heat release rate (HRR2) from 454.8 to 264.9 kW/m2, without a reduction in the material properties. In addition, this leaching-resistant furfurylated wood exhibited higher fire retardancy compared to conventional furfurylated wood. A potential method for producing fire-retardant treated furfurylated wood stable to water exposure has been suggested. Validerad;2022;Nivå 2;2022-05-02 (hanlid);Funder: CT WOOD, Luleå University of Technology; European Structural and Investment Fund, OP RDE (CZ.02.1.01/0.0/0.0/16_019/0000803);Part of special issue: Performance and Application of Novel Biocomposites II Advanced Research Supporting the Forestry and Wood Processing Sector’s Adaptation to Global Change and the 4th Industrial Revolution

ISBN för värdpublikationen: 978-609-02-1762-7

ISBN för värdpublikation: 978-952-94-4383-3

Weathering of wood is a complex natural phenomenon that is influenced by factors both in macro and micro-scale. The degradation by weathering constitutes of complex physical-chemical changes influenced by environmental factors such as moisture, sunlight, temperature, chemical compounds, wind, and biological organisms and their related agents. The aim of our study was the evaluation of MIR and NIR spectroscopic technique for characterisation of wood treated by commercial coatings contained different biocidal treatments after weathering in subarctic conditions. Tangential and radial surfaces of the Scots pine and Norway spruce were treated with coatings containing various biocides. Treatment was in the form of fairly transparent wood oil (T), while the two others were coatings that had more of a non-transparent character (H and P). Treatedspecimens and control were placed in various directions on racks outdoor for natural weathering. The measurement of the NIR spectra of specimens that were not exposed, after weathering and dried after weathering, was done by the point-based microNIR portable sensor. Multivariate statistical analysis (MSA) showed that data from types of exposure contributed to less compared to surface treatments in the 3D principal component analysis model (PCA). Grouping pattern around treatments H and P could be obtained as the two individual groups more or less fully separated. From the treatment T and non-treated specimens, no individual grouping behaviour could be observed, however, more intense exposed seemed to be clustered in a different way than mildly exposed ones. A more extensive weather exposure gave also a more degraded surface for T-treated specimens. The NIR portable spectrometer may be used for assessment of the extent of weathering, but the treatment P followed by treatment H had minimal changes. Coefficients Plot in the PLSDA model for different types of exposure for those treatments showed the influence of the NIRwavelengths in classes related to exposure type. The changes caused by weathering phenomenon was evaluated by using multivariate methods in which resulting multivariate model parameters for prediction of the changes were determined. Analysis of the chemical structure of coatings after weathering analysed by mid-infrared spectroscopy gave support to the lower stability of T-treatmentduring weathering. ISBN för värdpublikation: 978-1-7340485-0-6

The increased concern regarding mould on wood-based building materials has raised a demand for sustainable biocidal treatments to protect early contamination during the construction stage of timber buildings. By providing surface protection for all type of wood-based construction elements already at the construction site will reduce the mould-associated risk for not only the construction elements but also for the indoor climate and dwellers at the use-stage of the building. The purpose was to test the protective effect of commercial water-based treatments containing different biocides on single mould fungi growth in pure culture. Small specimens of Scots pine sapwood and heartwood, and Norway spruce were treated with four treatments, and a fungal test performed in 90 mm Petri plates. Two samples (treated and untreated control) placed on the plate with a distance between each other, and between, a fungal inoculum placed. Five pure cultures of fungi species used in the study: Aureobasidium sp., Trichoderma sp., Aspergillus sp., Cladosporium sp., Penicillium sp. The specimens exposed at the temperature of 24°C and relative humidity of 90%. The treatments contained biocides, i.e.: treatment 1: tetramethylol acetylenediurea and iodopropynyl butyl carbamate (IPBC), treatment 2: mixture of several biocides (IPBC, benzisothiazolinone (BIT), methylisothiazolinone (MIT) and 5-chloro-2-methyl-1,2-thiazol-3-one (CMIT)/MIT mixture), treatment 3: IPBC; and treatment 4: mixture of propiconazole and IPBC. The fungal growth observed in the untreated samples after four days of incubation, the specimens with treatment 4 attacked after eight days, when treatment 1 and 3 had free from fungal mycelia inhibition zone after 22 days of incubation. The moisture content after the test was similar for treated samples in plates with Aureobasidium sp., Aspergillus sp., Cladosporium sp., Penicillium sp., but was significantly higher for Trichoderma sp. The type of wood did not influence fungal growth in comparison to the type of treatment.