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Thermal modification is the most important commercial modification procedure. Thermally modified (TM) wood has improved durability, but its performance does not meet expectations predominately under moist conditions. To reduce water uptake of TM wood, Norway spruce specimens were treated with suspensions of a natural wax by dipping impregnation (DipI) or by vacuum-pressure impregnation (VPI). Wax-treated specimens were subsequently TM at 185, 200, 215, and 230°C. Control specimens were heated up to 100°C only. Contact angle (CA), short-term and long-term water uptake, bending strength, and performance against wood decay fungi of the resulting material were determined. The results show that a combination of wax treatment and thermal modification have a synergistic effect that considerably improves hydrophobicity, reduces liquid water uptake, slows down water vapor uptake, and improves the resistance against fungal decay of the treated material. [ABSTRACT FROM AUTHOR]

The development of non-biocidal and environmentally friendly systems to protect wood against biological decay has become a high priority in recent years. In the present study the impact of an innovative modification procedure, combining two environmentally friendly modification methods: thermal modification and mineralisation, using an aqueous solution of calcium acetoacetate as a precursor, on the fungal durability of wood was evaluated. European beechwood (Fagus sylvatica) and Norway sprucewood (Picea abies) were selected as model wood species. Wood samples were treated using either a single or combination of both methods and exposed to four different fungi: Gloeophyllum trabeum , Rhodonia placenta , Trametes versicolor and Pleurotus ostreatus. The effect of the different modifications on moisture content, dynamic vapour sorption, contact angle and pH value was also evaluated. Overall, the highest durability against Rhodonia placenta , Trametes versicolor and Pleurotus ostreatus was achieved through thermal modification in both wood species, while the combination of mineralisation and thermal modification has a synergistic effect against degradation by Gloeophyllum trabeum. In the case of beechwood the mass loss decreased from 41% for native to 6% for combined modified samples. We proved that the effectiveness of different treatment against fungal decay of wood were in strong dependence of their moisture content, dynamic vapour sorption, contact angle and pH values. The role of fungi on the morphology of the wood and on crystal structure of formed carbonate was investigated using SEM-EDS analysis. [Display omitted] • Presented ecological modification of wood can be an alternative to biocides. • A significant improvement in the fungal durability of wood was achieved. • Thermal modification and mineralisation work synergistic against wood decay fungi. • The reasons for a synergistic effect of combining methods were proposed. • The mass loss decreased from 41% for native to 6% for combined modified beechwood. [ABSTRACT FROM AUTHOR]

Simple Summary: Over the past thirty years, the thermal modification of wood has become a universally recognised and commercialised wood modification process. Thermal modifications may affect wood properties, either positively (dimensional stability and decay resistance) or negatively (mechanical properties). The combination of the impregnation of specific reagents with thermal modification may help to overcome the negative effects on wood properties. In this study, we evaluate the effect of a combination of two zwitterionic buffers, bicine and tricine, and thermal modification of two wood species (beech and spruce) against subterranean termites and their symbiotic fauna. Bicine and tricine treatments alone had a clear influence on wood mass loss and termite survival. The flagellate protist symbiotic community was affected by the treatments and responded differently to them, as a highly adaptable community. However, the combination of bicine with the thermal modification showed a negative effect on termites and their symbionts on both wood species. The combination of these different factors should be further investigated, as these results seem to be promising with regard to the enhancement of the termite resistance of wood. The majority of thermal modification processes are at temperatures greater than 180 °C, resulting in a product with some properties enhanced and some diminished (e.g., mechanical properties). However, the durability of thermally modified wood to termite attack is recognised as low. Recent attempts at combining thermal modification with chemical modification, either prior to or directly after the thermal process, are promising. Buffers, although not influencing the reaction systems, may interact on exposure to certain conditions, potentially acting as promoters of biological changes. In this study, two zwitterionic buffers, bicine and tricine, chosen for their potential to form Maillard-type products with fragmented hemicelluloses/volatiles, were assessed with and without thermal modification for two wood species (spruce and beech), with subsequent evaluation of their effect against subterranean termites (Reticulitermes grassei Clément) and their symbiotic protists. The effect of the wood treatments on termites and their symbionts was visible after four weeks, especially for spruce treated with tricine and bicine and heat treatment (bicine HT), and for beech treated with bicine and bicine and heat treatment (bicine HT). The chemical behaviour of these substances should be further investigated when in contact with wood and also after heat treatment. This is the first study evaluating the effect of potential Maillard reactions with zwitterionic buffers on subterranean termite symbiotic fauna. [ABSTRACT FROM AUTHOR]

In this study, the combined effects of chemical (with tricine and bicine) and thermal treatments were investigated. The modifications which appeared in the wood structure were evaluated by infrared spectroscopy and chemometric methods (principal component analysis and hierarchical cluster analysis). After the treatment, about 6–7% of WPG was identified in treated samples, but further thermal treatment decreased the WPG to about 5%. The modifications appearing in the spectra were mostly related to increase of the intensities of the bands assigned to C O groups but also to N–H and C–N groups, with shifting of some bands to higher wavenumber values. Image 1 • The combined effects of chemical and thermal treatment on soft and hardwood were evaluated. • The effectiveness of treatment was evaluated by infrared spectroscopy and chemometric methods. • The occurrence of the reactions between the functional groups from bicine and tricine and wood structure were identified. • Softwood samples were more susceptible to chemical/thermal modification than the hardwood samples. [ABSTRACT FROM AUTHOR]

Results of the research aimed to increase the resistance of beech and thermally modified (TM) beech wood to UV-light and weathering with impregnation with commercially available nano TiO2 suspensions, originally intended to be used as UV protective coating additives, are presented in this paper. Beech wood and TM beech wood samples were vacuum-pressure impregnated with suspensions, containing around 3% of TiO2, and in one series, the specimens were at first impregnated and thermally modified afterwards. In general, resistance to UV-light, as demonstrated by visual observation and by colour measurements was increased. Contact angle of water, liquid water absorption, and water vapour sorption also importantly influence on weathering behaviour of wood and it was shown that in general, impregnation with TiO2 particles has a positive influence with this respect. Anyway, some results of this preliminary research were ambiguous, and subsequent investigations of this novel protection method are needed and planned. [ABSTRACT FROM AUTHOR]