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Poor condition of roofs in terms of decay of shingles and loss of tar-based surface treatments has been revealed in a number of churches at various geographical locations in mid-Sweden. The condition of tars obtained from shingles of selected churches in mid-Sweden were analysed and obtained data were compared with geographical locations of the churches. According to gas chromatography-mass spectroscopy result, dehydroabietic acid was the dominant compound found in the exposed tars from the churches except in church of Malung where similar amounts of retene was found. Oxidised resin acids were found in exposed tars from the churches but not in commercially available pit burned tar. Tar from church shingles had higher char residues than the pit burned tar which was totally consumed when heated under nitrogen gas up to 750°C using thermogravimetric analysis. Scanning electron microscopy with energy dispersive X-ray spectrometer analysis revealed higher amounts of silicates in some exposed tars; however, these compounds constituted only a minor portion of the organic matter in these specimens. Based on the data obtained in the study other factors rather than simply geographical location of churches seemed to be of importance to explain differences of the investigated properties of the church tars., Validerad;2024;Nivå 2;2024-06-27 (hanlid);Full text license: CC BY, Biobasedfire protection of wood panel for exterior conditions by using phosphorylated lignin from wheat straw

Resultat angående ett antal utvalda TCN-företag (Stenvalls, Setra, Bergkvist Siljan, Holmen, Norra Timber och Derome) om deras produktion av aska och hanteringen av aska från förbränning av sågverksavfall har gjorts med hjälp av utskickat frågepaket. Produktionen av aska varierar men sammanslagen våtaska dominerade vidare hantering av askavfall. Askhanteringen sköttes såväl i egen regi som av återvinningsföretag beroende på sågverk och deras produktion. Egen hantering som material för utfyllnad eller ljudvall gör att kostnaden kan hållas låg men för företag där återvinningsföretag är iblandande kan kostnad för ett normalstort sågverk ligga på kring 800 kkr per år. Slutligen så visade studier av brandskyddande förmåga av fraktionerade asktillsatser vid tillverkning av spånskivematerial lovande resultat och att tillväxten av mögel-svampar kan hämmas vid tillsatser över 5%.

To improve the resistance of wood to biological decay the Maillard reaction between introduced amines and wood cell-wall polymers can be utilised. However, initial studies in wood modification showed almost complete leaching of bicine and tricine from treated wood and the loss of beneficial effects. The objective of this study was to assess whether possible reactions of bicine or tricine with wood could be further enhanced and reaction products stabilised through the addition of glucose and/or citric acid. Thus, Scots pine sapwood specimens were impregnated with tricine or bicine, with or without glucose and citric acid, and then heated to a temperature of 160°C. The dimensional stability, degree of chemical leaching and mechanical properties were assessed. Overall, it was concluded that neither the presence of glucose nor citric acid did appear to enhance the reactivity of tricine or bicine. Anti-swelling efficiency (ASE) of 50% was observed for combined treatments of bicine/tricine and citric acid but the leaching resistance originated mainly from citric acid and glucose, with no indication for the retention of bicine or tricine. The presence of citric acid led to a strongly reduced modulus of rupture., Validerad;2024;Nivå 2;2024-08-15 (sofila);Full text license: CC BY-NC-ND License

The rise in energy consumption and the increase in the use of bio-based materials in the building sector, has led to the need to investigate the possibilities to use wood as a porous support material for phase change materials (PCMs), and thereby creating a thermal regulative wood-based product. This study investigated the influence of Kraft lignin-glyoxal prepolymer on the thermal-energy storage properties of wood modified with paraffin-type of PCM. The implementation of the modified wood involves preparing PCM emulsions, synthesising lignin-glyoxal prepolymer, and modifying wood with the PCM-Kraft lignin-glyoxal emulsion through vacuum-pressure impregnation. The infrared imaging suggested the ability of PCM-modified wood to delay the temperature changes, even with the introduction of Kraft lignin-glyoxal prepolymer. In conclusion, it is feasible to introduce thermal-energy storage property into wood with the addition of Kraft lignin-glyoxal prepolymer. Further studies will focus on the long-term thermal storage performance properties when this PCM system is subjected to repeated heating/cooling cycles., Validerad;2024;Nivå 2;2024-07-02 (hanlid);Funder: Swedish Wood Industry;Full text license: CC BY-NC-ND

Funder: CT WOOD;ISBN for host publication: 978-961-6379-82-3

The exterior application of fire-retardant (FR) timber necessitates it to have high durability because of the possibility to be exposed to rainfall. In this study, water-leaching resistance of FR wood has been imparted by grafting phosphate and carbamate groups of the water-soluble FR additives ammonium dihydrogen phosphate (ADP)/urea onto the hydroxyl groups of wood polymers via vacuum-pressure impregnation, followed by drying/heating in hot air. A darker and more reddish wood surface was observed after the modification. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state 13C cross-polarization magic-angle-spinning nuclear magnetic resonance (13C CP-MAS NMR), and direct-excitation 31P MAS NMR suggested the formation of C–O–P covalent bonds and urethane chemical bridges. Scanning electron microscopy/energy-dispersive X-ray spectrometry suggested the diffusion of ADP/urea into the cell wall. The gas evolution analyzed by thermogravimetric analysis coupled with quadrupole mass spectrometry revealed a potential grafting reaction mechanism starting with the thermal decomposition of urea. Thermal behavior showed that the FR-modified wood lowered the main decomposition temperature and promoted the formation of char residues at elevated temperatures. The FR activity was preserved even after an extensive water-leaching test, confirmed by the limiting oxygen index (LOI) and cone calorimetry. The reduction of fire hazards was achieved through the increase of the LOI to above 80%, reduction of 30% of the peak heat release rate (pHRR2), reduction of smoke production, and a longer ignition time. The modulus of elasticity of FR-modified wood increased by 40% without significantly decreasing the modulus of rupture., Validerad;2023;Nivå 2;2023-04-21 (joosat);Funder: OP RDE (Grant no.CZ.02.1.01/0.0/0.0/16_019/0000803); CT WOOD, Luleå University of TechnologyLicens fulltext: CC BY License

This study determined the impact of undertaking an initial treatment of oak wood by sealing its surface pores with epoxy resin, focusing on the durability of transparent coating systems when exposed outdoors. Throughout the exposure period, various parameters including color, gloss, surface wettability, and both macroscopic and microscopic surface evaluation were continuously monitored. The study involved two sets of samples: one set underwent the pretreatment, while the other did not. Subsequently, four coating systems were applied to the samples, comprising two solvent-based and two water-based coatings. The experiment was conducted over a period of two years, utilizing natural weathering methods within the premises of the Czech University of Life Sciences in Prague. The pretreatment with epoxy resin exhibited enhanced durability for all paint systems. The analysis showed a significant difference in gloss and color after 12 months of weathering exposure without any significant effect on surface wettability and sealing. However, after 24 months of the weathering exposure, no significant differences between the sealed and unsealed surface were observed. The most significant change in properties was noted for the water-based coatings used in coating systems number 3 and 4, and these coatings were rated as the best., Validerad;2023;Nivå 2;2023-08-07 (hanlid);Funder: Technology Agency of the Czech Republic

Chemical modification of wood typically requires the impregnation of wood with reactive compounds capable of undergoing covalent bonding to functional groups present in the cell wall. Creating such reactive agents in situ, with the use of low-priced chemicals, would prove more attractive for commercial applications. In this study, Scots pine (Pinus sylvestris L.) sapwood was impregnated with an aqueous solution of urea (30%), dried at 40°C for 24 h, and subsequently heat treated in an oven at 150°C for 24 h to produce the reactive isocyanic acid. By using accelerated fungal tests under laboratory conditions, provisional tests demonstrated a high biological resistance against selected moulds and rots. Migration of urea into the wood structure and grafting to its polymers during subsequent heat treatment, led to a bulked cell wall and enhanced resistance to water swelling, even after cycling water treatments. The bending strength (MOR) of modified pine wood was reduced by the treatment applied, while its modulus of elasticity (MOE) remained unchanged., Validerad;2023;Nivå 2;2023-06-30 (joosat);Licens fulltext: CC BY-NC-ND License, Biobased fire protection of wood panel for exterior conditions by using phosphorylated lignin from wheat straw

Fire-retardant (FR) treated wood-based panels, used commonly in furniture and construction, need to meet stringent fire safety regulations. This study presents a novel treatment for imparting fire resistance to wood composites by applying separate solutions of phytic acid and sodium silicate onto wood particles before the hot pressing at 160 °C. A scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analysis revealed that phytic acid and sodium silicate were uniformly distributed throughout the wood particles, and the formation of silica gel resulted in the aggregation of elemental silicon. Fourier-transform infrared spectroscopy (FTIR) displayed that phytic acid caused the thermal degradation of hemicelluloses, which led to a brownish outer appearance of the FR-treated composites. Fire performance was assessed using both limiting oxygen index (LOI) and a cone calorimeter. These techniques showed a higher LOI value and a significant reduction in heat-release rate (HRR), total heat release (THR), smoke-production rate (SPR), and total smoke production (TSP). In addition, cone calorimeter and thermogravimetric (TGA) analyses consistently showed increased char residue in treated wood composites. Moreover, internal bond strength (IB) and modulus of elasticity (MOE) of the wood composite were not significantly changed compared with those of the untreated composite. Surprisingly, in the FR-treated composite, the 24 h-thickness swelling, and the water uptake were slightly decreased. Consequently, this new treatment has the potential to increase the fire retardancy of wood composites, such as particleboard, without deteriorating the key mechanical properties., Validerad;2023;Nivå 2;2023-05-22 (hanlid);Funder: Slovak Research and Development Agency (APVV-16-0223); VEGA agency (VEGA 1/0678/22); KEGA agency (KEGA 016STU4/2021); Swedish wood industry; OP RDE (CZ.02.1.01/0.0/0.0/16_019/0000803), Biobased fire protection of wood panel for exterior conditions by using phosphorylated lignin from wheat straw, Advanced research supporting the forestry and woodprocessing sector’s adaptation to global change and the 4th industrial revolution

Wood is a naturally based material and plays an important role as a renewable resource when aiming for a sustainable society. Nevertheless, its inherently combustible property needs to be enhanced to comply with modern construction methods and regulations. Ammonium phosphate-based additives are often used to effectively increase the fire-retardancy (FR) of wooden products when needed. However, their water-solubility make them unsuitable for exterior use unless such properties are overcome. This PhD thesis focuses on the development of methodologies to alleviate consequences from water-leaching of wood treated with ammonium phosphate-based additives, enabling further development of new types of fire protected wood construction material for exterior uses. As such, two methodologies were explored in this thesis: 1) a composite-type fixation, involving the introduction of a hydrophobic polymer matrix for entrapping the FR additives, 2) a reactive-type fixation, which is to fix the FR additives by creating covalent bonding with the wood polymeric constituents. In order to determine the influence of composite-type fixation systems, melamine-formaldehyde (MF) prepolymer, furfuryl alcohol (FA), and kraft lignin, respectively, were studied for immobilising ammonium phosphate-based FR-additives in wood by pressure impregnating Scots pine (Pinus sylvestris L.) sapwood with a solution of the prepolymer and fire-retardant additives (FRs), followed by drying and heating steps. Through the analysis of the treated wood materials, involving scanning electron microscopy energy dispersive spectroscopy (SEM-EDX) and thermal gravimetric analysis (TGA), the formation of a stable polymeric network structure entrapping the additives inside the wood with alleviating FRs’ water-leachability was proposed. In particular, MF-resin was able to encapsulate guanyl-urea phosphate (GUP) in the lumen of the wood. Further details on the distribution and structural features of FR additives and matrices