Increasing the water uptake of wood veneers through plasma treatment at atmospheric pressure

In order to provide a database which documents the influence of plasma treatment on water uptake of wood veneers, veneers of 27 wood species underwent immersion tests in untreated and plasma-treated states. Plasma treatment was executed using an air driven dielectric barrier discharge at atmospheric pressure. The results showed that plasma treatment led to significantly improved water uptake for most of the wood species, but some wood species remained unaffected after plasma treatment.     

Processing of wood plastic composites: The influence of feeding method and polymer melt flow rate on particle degradation

Spruce wood particle (WP)/polypropylene (PP) compounds were prepared in an internal mixer using different rotor speeds. To analyze the effect of feeding method on particle degradation, WP and PP were either fed as dry‐blend or WP was fed into the PP melt. To prevent melt freezing, pre‐heated WP were used as comparison to cold WP. In addition, WPs were compounded with different grades of PP or high‐density polyethylene (HDPE) to analyze the effect of polymer matrix melt flow rate (MFR) on particle degradation. Mixing behavior of compounds containing 30% and 70% (w/w) WP depended on feeding method, represented by a changing relation of final torque values. Feeding as dry‐blend and using pre‐heated particles led to stronger WP degradation. Degradation decreased with increasing polymer MFR. For PP compounds, particle degradation was stronger when containing 70% WP, for HDPE the difference due to WP content was only marginal. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43231.     

Verklebung von wachsimprägnierter Buche unter Variation der Klebesysteme und Durchführung einer Plasmabehandlung

Beech wood was impregnated with two hot melting waxes. Contact angle measurement followed to determine hydrophobizing of such treated wood. Tensile shear tests were carried out to test the adhesion properties with three different glues under varying environmental conditions. Furthermore, wax impregnated beech was subjected to plasma treatment prior to glueing. The results demonstrate that wood treated with polar paraffin shows lower adhesion properties compared to montan wax. Therefore, montan wax was investigated more intensely. Beech impregnated with such wax can be used for constructive building elements in the interior sector. D3 Glues for non-constructive applications were realized by using PVAc and phenol-resorcinol resin under permanent influence of humidity. Plasma treatment improves this quality to obtain D4 glue. Back-drying of the water stored specimens proves the suitability of isocyanate glue and also that of PVAc after plasma treatment for 120 s.     

Water vapor sorption kinetics of wood modified with glutaraldehyde

The modifying effects of Scots pine (Pinus sylvestris L.) wood with the crosslinking agent glutaraldehyde (GA) on the water vapor sorption kinetics were studied by curve fitting the experimental isotherm sorption data obtained using a Dynamic Vapor Sorption apparatus using the parallel exponential kinetics model (PEK model) and the Hailwood–Horrobin model (H–H model) for the isotherm. Both the H–H model and the PEK model provided good fits to the experimental data. Modification of wood with GA reduced both the time to equilibrium and the equilibrium moisture content (EMC). According to the PEK and H–H models, the reduction in EMC was mainly due to the decrease of moisture content (MC) associated with the slow sorption processes and polylayer water. The fast sorption processes and monolayer water were little affected by GA modification. Compared to the untreated control, the estimated total water absorbed by wood treated to a WPG of 20.9% at 100% RH decreased by 52.2%, by extrapolating the fitted curves derived from the H–H model. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Bioassaying combinations of wood preservatives and tannins withPoria placenta andAspergillus niger

With “new” preservatives it is convenient to be able to screen their efficacy before time consuming and expensive fungi tests are carried out. For a fast screening of preservatives, combined with natural and synthetical tannins, two screening tests withAspergillus andPoria, respectively, had been used. The results had been compared with soil block tests. With both screening tests, reproducible and distinctive results are given even after a couple of days. However, the comparison with the soil block test showed, that the result from the screening tests are not reliable for a later use of timber in soil contact.     

Weathering of silane treated wood

Outdoor and artificial weathering tests were performed on specimens of Scots pine sapwood treated with silanes to achieve water repellent properties. During outdoor weathering, the treatment caused a reduction in (liquid) water uptake but the sorption of moisture (air humidity) was not affected by silane treatment. The water repellent effect of vacuum-pressure treated specimens remained stable over the tested exposure period of one year, as was shown in dipping tests. Evaluation of silane treated specimens did not reveal any reduction of crack formation during exposure to weathering. The application of silanes in combination with UV light stabilizers enhanced the effectiveness of these protectants and led to higher colour stability during artificial weathering in a QUV device.     

Der Einfluß enzymatischer Behandlungen auf die Tränkbarkeit k;einer Fichtenproben

The permeability of spruce wood (Picea abies L. Karst) was considerably improved by pretreatment with enzymes. Sapwood was improved to greater extent than heartwood. The most succesful were commercial preparations of cellulase, hemicellulase and pectinase mixtures. Different concentrations, buffers and temperature ranges were tested. The best results were reached with 1% suspensions in buffer at 25–40 “C.