VOLUME 61, ISSUE 4/2020

Wood preservatives containing copper are used as the dominant product for preserving wood in outdoor areas due to their effectiveness and economic availability. Nowadays there is a need for ecological wood preservatives because of the avoidance of questionable biocides such as chromium and arsenic compounds. The aim of the project was to create the scientific prerequisites for wood preservatives based on natural raw materials through creative approaches. In the course of the project a number of copper-ligand systems with fungicidal properties could be identified in which the ligands are based on renewable raw materials and are harmless to humans. Furthermore, the first approaches for reactive impregnation systems have been developed, which prevent the protective agents from being more easily washed out by depot effects in the wood.

PMDI-bonded fibreboards were made from unwashed and washed recycled fibres, obtained by thermo-mechanical pulping (TMP) of a mixture of UF-bonded particleboards and chips from pinewood. A part of the fibre boards was subjected to a thermal treatment for five days at 70 °C and 90 °C in a drying cabinet. The fibreboards were tested for their physical-mechanical properties, formaldehyde release and their content of hot water-soluble extractives. The results clearly indicate that washing of the fibres with water before blending has a tremendous positive influence on the internal bond strength as well as on the boiling strength of the boards, it also reduces drastically the thickness swelling and water absorption of the fibreboards. Thermal treatments at 70 °C and 90 °C have also a positive effect on the internal bond strength of the boards. However, the effect lags behind that of washing the fibres. The results, moreover, reveal that a partial removal of the degradation products of recycled fibres by washing enhances their physical accessibility and the chemical reactivity towards bonding

with PMDI, leading to a fibre-to-fibre bond with high moisture resistance.

Wood preservatives containing copper are used as the dominant product for preserving wood in outdoor areas due to their effectiveness and economic availability. Nowadays there is a need for ecological wood preservatives because of the avoidance of questionable biocides such as chromium and arsenic compounds. The aim of the project was to create the scientific prerequisites for wood preservatives based on natural raw materials through creative approaches. In the course of the project a number of copper-ligand systems with fungicidal properties could be identified in which the ligands are based on renewable raw materials and are harmless to humans. Furthermore, the first approaches for reactive impregnation systems have been developed, which prevent the protective agents from being more easily washed out by depot effects in the wood.

The development of environment-friendly antimicrobial products to replace conventional biocides is a central challenge of research and development in wood and material protection. Against this background, an appropriate strategy was developed in a basic research project to isolate Actinobacteria with antagonistic efficacy against typical material-damaging microorganisms in wood and material protection, to determine their antimicrobial activity spectrum and to identify favourites for the application in different material protection areas (wood protection, film protection, pot preservation). Screenings with more than 100 Actinobacteria isolated mainly from microbially damaged materials showed that more than 50 % of the examined strains had antimicrobial activities. The highest efficacy against wood-destroying and wood-discouloring fungi was found with Streptomyces violaceusniger and Streptomyces rochei. The extract fractions obtained from these Actinobacteria were also effective against material damaging bacteria and – to a lesser extent – against yeasts and moulds, but not against wood-destroying fungi. This indicates inadequacies of the used extraction regime and requires further investigations with varied extraction agents and conditions. Based on the results obtained so far, application-oriented developments can be pursued, which are aimed at protecting against bacterial material damage. This concerns in particular in-canpreservation of paints and varnishes.

We were amaing to update the comprehensive characterization of WPC deckings from 2008 to be able to get an overview of developments in that field. Extensive analyses of commercially available European deckings were done to get an impression of their technical and commercial performance. To get representative samples from the market, those were purchased via official distribution channels. We compared the geometry (dimensions, weight per linear meter, etc.) the compositions (wood content, type of polymerused) and the properties most important for this application (mechanical properties, water soption, swelling, weathering, chalking, etc.). All tests are according to EN 15534-1 (2017) and to the quality sign of Verband der Deutschen Holzwerkstoffindustrie (VHI), Germany. An overview of the WPC deckings, also compared to the most common solid wood deckings in Europe (e. g. larch, Bangkirai), and their properties is given here in the form of anonymous benchmark diagrams. These diagrams also include the comparison to the results from 2008.

In 13 parts were presented the main high educational centers for wood science and technology of 33 European countries. Part 14 to 21 presented an introduction regarding the North American forest and

wood industry as well the Canadian and USA institutions for wood science and research. Part 22 to 31 started an overview in Asia (Japan, Thailand, Iran, Vietnam, Mongolia and China) and this paper is

continuing with aspects of the wood industry in China.