Diffusionsverhalten von IPBC in wasserbasierten Beschichtungssystemen auf Holzfassaden

Zusammenfassung: Wasserbasierte Beschichtungssysteme auf Holzbauteilen sind einem verstärkten Befall durch Schimmel- und Bläuepilze ausgesetzt. Durch einen gezielten Einsatz von Bioziden ist es möglich, einen Befall auf und unter der Beschichtung zu kontrollieren. Jodpropinyl-N-butylcarbamat (IPBC) ist eines der wichtigsten Biozide für den Filmschutz von wasserbasierten Systemen in Europa. In der vorliegenden Arbeit wurde das Diffusionsverhalten von IPBC untersucht. Dabei wurde festgestellt, dass eine Diffusion des IPBC aus der Grundierung in die Deckschicht erfolgt. Die Verteilung des Wirkstoffes in der Deckschicht ist relativ gleichmässig. Die Eindringung in das Holzsubstrat (Fichte) ist mit 250µm sehr gering und die nachgewiesene Wirkstoffmenge in diesem Bereich variiert deutlich. Das Diffusionsverhalten von IPBC ist an einen Wasserdampfstrom und ein notwendiges Konzentrationsgefälle in der Beschichtung gekoppelt. Durch Bewitterungsversuche wurde nachgewiesen, dass bereits nach dreimonatiger Bewitterung nur noch 30% IPBC in der Deckschicht nachgewiesen werden konnte

Physisporinus vitreus: a versatile white rot fungus for engineering value-added wood products

The credo of every scientist working in the field of applied science is to transfer knowledge "from science to market,” a process that combines (1) science (fundamental discoveries and basic research) with (2) technology development (performance assessment and optimization) and (3) technology transfer (industrial application). Over the past 7years, we have intensively investigated the potential of the white rot fungus, Physisporinus vitreus, for engineering value-added wood products. Because of its exceptional wood degradation pattern, i.e., selective lignification without significant wood strength losses and a preferential degradation of bordered pit membranes, it is possible to use this fungus under controlled conditions to improve the acoustic properties of tonewood (i.e., "mycowood”) as well as to enhance the uptake of preservatives and wood modification substances in refractory wood species (e.g., Norway spruce), a process known as "bioincising.” This minireview summarizes the research that we have performed with P. vitreus and critically discusses the challenges encountered during the development of two distinct processes for engineering value-added wood products. Finally, we peep into the future potential of the bioincising and mycowood processes for additional applications in the forest and wood industr

Resistance of thermo-hygro-mechanically densified wood to colonisation and degradation by brown-rot fungi

Colonisation and wood degradation by three brown-rot fungi, Coniophora puteana, Gloeophyllum trabeum and Poria placenta, were studied in wood of Norway spruce (Picea abies) subjected to three different treatments: hygro-thermal (TH) (160 and 180°C), mechanical densification and thermo-hygro-mechanical (THM) treatment including densification and post-treatment under saturated steam conditions at different temperatures (140, 160 and 180°C). The weight loss induced by all three fungi was lowest in THM-densified wood post-treated at 180°C. Highest weight losses were recorded for controls and TH-treated wood. Fungal colonisation varied in its intensity, depending on the treatment applied to the wood. Hyphal growth in controls and TH-treated wood was abundant, whereas in densified and THM-densified wood it was sparse and confined predominantly to the cell lumina of earlywood tracheids. Also, penetration of large-diameter hyphae and associated degradation in THM-densified wood was impeded by occlusion of the lumina, associated with irreversible compression (loss in shape memory). In contrast to C. puteana and P. placenta, which showed typical brown-rot behaviour, G. trabeum frequently showed hyphal tunnelling within the secondary walls of tracheids and xylem ray parenchyma of controls and thermally treated wood. Such growth was never observed in THM-densified wood post-treated at 180°

Radial basis function neural networks for modeling growth rates of the basidiomycetes Physisporinus vitreus and Neolentinus lepideus

A radial basis function (RBF) neural network was developed and compared against a quadratic response surface (RS) model for predicting the specific growth rates of the biotechnologically important basidiomycetous fungi, Physisporinus vitreus and Neolentinus lepideus, under three environmental conditions: temperature (10-30°C), water activity (0.950-9.998), and pH (4-6). Both the RBF network and polynomial RS model were mathematically evaluated against experimental data using graphical plots and several statistical indices. The evaluation showed that both models gave reasonably good predictions, but the performance of the RBF neural network was superior to that of the classical statistical method for all three data sets used (training, testing, full). Sensitivity analysis revealed that of the three experimental factors the most influential on the growth rate of P. vitreus was water activity, followed by temperature and pH to a lesser extent. In contrast, temperature in particular and then water activity were the key determinants of the development of N. lepideus. RBF neural networks could be a powerful technique for modeling fungal growth behavior under certain parameters and an alternative to time-consuming, traditional microbiological technique

Assessment of resonance wood quality by comparing its physical and histological properties

The quality of wood used for music instrument making (resonance wood) is determined by assessing six physical properties: density, modulus of elasticity, sound velocity, radiation ratio, emission ratio, and loudness index. This can easily be done by means of measurements of the resonance frequency and the corresponding damping factor. The method described here is based on vibrational analyses, adapted from standard non-destructive testing of solid material, so as to provide information both for scientific studies and for violin making. The above six properties were assessed in samples of resonance wood of different quality and in normal (control) wood of Norway spruce and sycamore. The differences observed between the samples correlated with anatomical or histological characteristics of the wood. A sample of best-quality Norway spruce resonance wood showed a high radiation ratio in the axial direction, which correlated with the presence of small wood cells with thin cell walls. In "curly maple”, a high sound velocity in the radial direction correlated with the presence of broad xylem rays. The influence of external factors like wood moisture content or the geometry of the system is discussed within the context of the present stud

Degradation of thermo-hygro-mechanically (THM)-densified wood by soft-rot fungi

Thermo-hygro-mechanical (THM)-densified wood is more resistant to colonisation and degradation by brown-rot fungi than untreated wood. Colonisation and degradation by soft-rot fungi was investigated in treated Norway spruce (Picea abies) and treated beech (Fagus sylvatica) to assess their suitability for utility class 4. Three different treatments were applied: thermal-hygro (TH) treatment, mechanical densification and THM-treatment including densification and post-treatment under saturated steam conditions at different temperatures. For comparison, additional wood specimens were treated with two concentrations of a chromium-copper (CC) wood preservative. After 32weeks incubation, weight losses induced by soft-rot fungi were lowest in wood treated with CC. Highest weight losses were recorded from TH-treated wood, in which soft-rot erosion attack (type 2) was exclusively observed in spruce. In comparison to controls, significantly lower weight losses by soft-rot fungi were recorded in THM-treated spruce wood, but no such differences were found in beech wood. Microscopical examination showed that in THM-treated wood of spruce, soft-rot type 1 commenced from the outer wood surfaces and cavity formation was not found in deeper regions of the wood samples. THM-treated beech wood was more susceptible to degradation than that of spruce which can be partly explained by the higher syringyl lignin content in beech wood, which is more susceptible to all kinds of degradation. Hyphal colonisation and soft-rot was facilitated within deeper regions of beech wood mainly in the non-occluded lumina of parenchyma cells in multiseriate xylem rays. It can be concluded that TH-treated spruce wood and THM-treated beech wood is susceptible to soft-rot and therefore inappropriate for utility class

Resistance of thermo-hygro-mechanically (THM) densified wood to degradation by white rot fungi

Colonisation and degradation by the white rot fungi, Trametes versicolor and T. pubescens, were studied in wood of Norway spruce and beech subjected to three different treatments: (1) hygro-thermal treatment (160°C and 180°C), (2) mechanical densification, and (3) thermo-hygro-mechanical (THM) treatment including densification and post-treatment at different temperatures (140°C, 160°C and 180°C). The weight losses induced by the fungi were lowest in THM-densified woods. However, volume related numerical indicators for decay susceptibility did not show any significant improvements of THM-densified woods against both fungi. Analysis of the chemical composition of treated wood species revealed slight alterations in the content of polysaccharides and lignin. White rot fungi circumvented conditions restricting hyphal growth within the occluded tracheid lumina by hyphal tunnelling in the secondary walls of fibre tracheids in beech or by forming bore holes that transversally penetrated cell walls of earlywood tracheids in THM-densified spruce. The studies indicate that THM-densified beech and Norway spruce wood may have some potential in utility class 3 but are inappropriate for use in utility class

Permeability changes in heartwood of Picea abies and Abies alba induced by incubation with Physisporinus vitreus

The present study shows that isolates of P. vitreus have an extraordinary capacity to induce substantial permeability changes in heartwood of P. abies without causing significant losses in impact bending strength. The degradation of pit membranes by P. vitreus is an important aspect that could also have significant benefits in wood protection processes. Further studies are currently in progress with the objective of optimising the uniformity of wood colonisation and duration of incubation, so as to improve the permeability of water-borne wood preservatives or hydrophobic substances applied by brushing, dipping and impregnatio

Imaging hyphal growth of Physisporinus vitreus in Norway spruce wood by means of confocal laser scanning microscopy (CLSM)

Light microscopy and electron microscopy are the most common methods for analyzing wood-decay fungi. However, the 3D visualization and quantification of the filamentous structure of fungi in wood is difficult to realize by means of these traditional techniques. In the present work, confocal laser scanning microscopy (CLSM) was further developed for the quantitative imaging of the 3D microscopic hyphal growth of Physisporinus vitreus, a versatile fungus for engineering value-added wood products. To this purpose, the fungus was stained with a fluorescent dye Alexa Fluor. The 3D information obtained by CLSM has a high potential as a basis for the development of mathematical models for a more precise observation of the growth behavior of wood-decay fung

A Review on Promising Approaches for Liquid Permeability Improvement in Softwoods

The low liquid permeability of refractory wood species such as Norway spruce [Picea abies (L.) Karst.] and white Fir (Abies alba) is related mainly to the aspiration of bordered pits during wood drying. The resulting low permeability complicates treatments with liquid preservatives or wood modification substances. This article provides a literature review on various mechanical and biotechnological approaches that were developed for improving liquid permeability. In this context, we focus on the incubation of Norway spruce wood with a white rot fungus, Physisporinus vitreus (Pers.) P. Karst. The process is termed "bioincising" and results in a significant increase in wood permeability. This is most probably caused by the selective degradation of bordered pit membranes and simple pits of xylem ray parenchyma during the initial period of wood colonization. Subsequently, we discuss how bioincising could be a potential pretreatment method for wood preservation and selected wood modification substances. Considering that these wood modification systems require specific penetration depths for optimal performance, we discuss the capability of bioincising to enhance permeability at the required penetration depths. In this regard, we propose a terminology for better differentiation of penetration depths by liquid substances into the wood