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Wood chips were treated with alkyl ketene dimer (AKD) using three different processes to impart water resistance to particleboards. In the first process, AKD was blended with UF resin. Thickness swelling and water uptake after a 24 h immersion period (20 and 69%) were lower than in the control boards (28 and 81%) but were higher than in the paraffin references (10 and 22%). In process 2, AKD and UF resin were sprayed separately on the chips resulting in a greater reduction of thickness swelling (15%) and water uptake (49%) than in process 1. Paraffin references revealed a thickness swelling and water uptake of 7 and 25%, respectively. An extension of the pressing time in processes 1 and 2 did not increase water repellence. In process 3, particleboards were made from AKD-treated chips that were cured at 130 °C (24 h) prior to gluing. They showed a thickness swelling of 7% and a water uptake of 25%, whereas particleboards with paraffin exhibited levels of 8 and 29%. The thickness swelling and water uptake of boards with AKD increased when the curing time was reduced from 24 to 12 to 6 h (130 °C). Changing the curing temperature from 130 to 100 °C (12 h) had no effect on board properties. The IB of boards made from pre-cured chips with AKD (24 h/130 °C) was 44% lower than in controls and 35% lower than in paraffin references. This indicates that AKD impedes the adhesion. Zusammenfassung Holzspäne wurden in drei unterschiedlichen Prozessen mit AKD behandelt, um die Dimensionsstabilität der daraus gefertigten Platten zu erhöhen. Im ersten Prozess wurde die AKD Dispersion im Untermischverfahren mit der UF Leimflotte auf die Späne aufgebracht. Die Dickenquellung und Wasseraufnahme nach 24 h (20 und 69%) war niedriger als die der Kontrollplatten (28 und 81%), aber höher als jene der Paraffinreferenzen (10 und 22%). Im 2. Prozess wurden erst das AKD und anschließend die Leimflotte aufgesprüht. Im Vergleich zur AKD-Behandlung im Prozess 1 zeigten diese Platten eine geringere Dickenquellung (15%) und Wasseraufnahme (49%). Die Paraffinreferenzen des Prozesses 2 wiesen eine Dickenquellung und Wasseraufnahme von 7 und 25% auf. Eine Verlängerung der Presszeiten in Prozess 1 und 2 führte zu keiner erhöhten Feuchtebeständigkeit der Platten. Im 3. Prozess wurden die Späne jeweils mit AKD und Paraffin besprüht und vor der Beleimung bei 130 °C für 24 h getrocknet. Die Dickenquellung und Wasseraufnahme der Platten aus AKD behandelten Spänen lag bei 7 und 25%, jene von Paraffinreferenzen bei 8 und 29%. Die Verkürzung der Trocknungszeiten bei 130 °C von 24 auf 12 und 6 h führte zu erhöhten Dickenquellungen und Wasseraufnahmen von Platten mit AKD. Die Verringerung der Trocknungstemperatur von 130 auf 100 °C (12 h) hatte keinen Einfluss auf die Platteneigenschaften. Die Querzugfestigkeiten von Platten aus AKD vorbehandelten Spänen (130 °C/24 h) waren im Vergleich zu Kontrollplatten und Paraffinreferenzen um 44 und 35% reduziert. Dies weist daraufhin, dass AKD die Verklebung mit UF Harz beeinträchtigt. peerReviewed

Thermo-mechanical (TMP) and chemo-thermo-mechanical pulps (CTMP) were prepared from pine wood and from UF-bonded MDF made from pine wood. For preparing TMP pine chips as well as UF-bonded MDF were digested under pressure at 170 °C. Thereafter, the digested chips and MDF were defibrated at 170 °C using a single disc refiner. CTMP was prepared from pine wood with 0.25% NaOH (based on dry wood) under the conditions set forth above. CTMP was also made from MDF under two conditions using 0.15% sodium hydroxide (% based on dry MDF) and a mixture of sodium sulphite (1%) and sodium hydroxide (0.25%). The pulps show distinct differences in their properties: TMP from UF-bonded MDF shows lower extractive content in cold and hot water, lower pH-value and higher buffering capacity towards alkali of the cold water extractives than the CTMP counterpart. Moreover, CTMP prepared by using sodium hydroxide alone as a pulping agent increases the content of formate and acetate ions in the cold water extractives. The use of a mixture of sodium sulfite and sodium hydroxide as a pulping agent decreases, however, significantly the content of formate and acetate ions in the cold water extractives. This may be due to the buffering action of sodium sulfite. In general, CTMP decreases the formaldehyde release of the fibres, as measured by the flask method. In presence of sodium sulfite as a pulping agent for recycled MDF, the formaldehyde release is slashed to almost 30% of its original value. The formaldehyde release of CTMP from UF-bonded boards seems to be in the same range as that of TMP from virgin wood. peerReviewed

The goal of this study was to characterise chemical and histochemical properties of five dipterocarp timber wood species (Dipterocarpus kerrii, Hopea plagata, Parashorea malaanoman, Shorea almon, and Shorea contorta) differing in wood service life and utilisation. Wood of H. plagata, the most durable species, contained the lowest concentrations of nitrogen and ligno-protein, the highest C/N ratio and the lowest lignin concentration per dry mass but the highest lignin and extractive concentrations per wood density. FTIR spectroscopic studies of wood and isolated lignins of D. kerrii and H. plagata revealed differences compared to P. malaanoman and Shorea sp., which are species with short service life. Lignins of the Shorea/Parashorea species had a higher G/S ratio than those of H. plagata and D. kerrii. This was also evident from histochemical staining. Principle component analysis of FTIR spectra identified differences in both lignin composition and ligno-protein content as major source of variation. peerReviewed

Chips from pine wood were subjected to thermo-mechanical pulping (TMP) at 140 and 180 oC for 5 minutes, whereas the cooked chips were defibrated using a single disk pressurized refiner at the same temperatures (140 and 180 oC). The fibres were tested for some of their morphological properties including fibre length, fibre width, cellwall thickness. Moreover, the fine fibre fraction (zero fibres) and the content of splinters were also estimated. The results reveal, that increasing the temperature during thermo-mechanical pulping decreases the fibre length, the cell width and the fibre wall thickness. It also increases the amount of fine fibres and increases the curl factor. peerReviewed

Die Untersuchungen betreffen die Eignung von TMP (thermo-mechanisch hergestellte Fasern) aus gebrauchten Holzspan- und -faserplatten als Rohstoff für die Herstellung von mitteldichten Faserplatten. Die Untersuchungsergebnisse lassen folgende Schlüsse zu: TMP aus gebrauchten Holzspan- und Holzfaserplatten weisen charakteristische morphologische und chemische Unterschiede zu TMP aus Holz auf. TMP aus Gebrauchtfaser- und -spanplatten sind kürzer in der Faserlänge und verfügen über einen höheren Feinanteil. Die Kaltwasserextrakte der TMP aus Gebrauchtspanplatten und Gebrauchtfaserplatten weisen einen deutlich höheren pH-Wert und einen höheren Gehalt an Acetat- und Formiationen auf. Auch die Formaldehydabgabe der TMP aus gebrauchten Span- und Faserplatten ist höher als die des aus Holz hergestellten TMP. TMP aus Holz lässt sich bei der Herstellung von UF-Harz-gebundenen MDF zu 30% durch TMP aus Gebrauchtspan- und -faserplatten ersetzen, ohne dass die mechanisch-technologischen Eigenschaften der hergestellten Platten eine nennenswerte Beeinträchtigung erfahren. Auch die Formaldehydabgabe der hergestellten Platten wird hierdurch nicht erhöht. Es sind weiterhin keine signifikanten Unterschiede in der Abgabe an flüchtigen Säuren zwischen den direkt aus Holz hergestellten Platten und denen unter Zusatz von TMP aus Gebrauchtspan- und -faserplatten gefertigten MDF feststellbar. Dies kann als hinreichendes Kriterium dafür angesehen werden, dass zwischen dem eingesetzten Bindemittel und den chemischen Abbauprodukten der Gebrauchtholzspan- und -faserplatten chemische Wechselwirkungen bestehen. peerReviewed

Thermo-mechanical (TMP) and chemo-thermo-mechanical pulping (CTMP) of UF-bonded MDF induce considerable degradation of the UF-resin in the board and lead to a conspicuous increase in the content of water extractives of the fibres. Moreover, the water extractives of the fibres have a higher pH-value and a lower buffering capacity as well as higher acetate and formate ions content than the extractives of the original board. However, the lignin content seems rather to increase than to decrease. This is possibly due to reaction between lignin and formaldehyde from the resin. peerReviewed

TMP (thermo-mechanical pulps) and CTMP (chemo-thermo-mechanical pulps) were made from pine wood and recycling MDF, which has been prepared from pine wood too. The fibres were tested for their wettability using the method developed by Roffael et al (2002). The results reveal that TMP are much less wettable in comparison to CTMP from the same wood. Moreover, fibres made from UF-bonded MDF by the TMP- and CTMP-process are of much higher wettability compared to TMP and CTMP prepared directly from wood. No significant difference in the wettability between TMP and CTMP from UF-bonded MDF was detected. This behaviour has been attributed to the fact that the UF-resin in MDF degrades during thermohydrolytic pulping leading to the formation of ammonia and free urea. Therefore, pulping of UF-bonded boards takes place under chemo-thermo-mechanical conditions (CTMP). peerReviewed

Porous carbon materials have a wide range of technical applications due to their properties including low density potential, mechanical capacity, resistance to heat and corrosion as well as electric conductivity. Zusammenfassung Poröse Kohlenstoffmaterialen finden aufgrund ihrer Eigenschaften vielfältige technische Anwendungen. Sie haben Leichtbaupotential, sind mechanisch belastbar, hitze- und korrosionsbeständig und elektrisch leitend. Als Grünkörper für karbidische Keramiken dienen typischerweise organische Materialien wie Phenolharz oder Polyacrylnitril. Es eignen sich jedoch auch Holz und insbesondere Holzwerkstoffe sowie die in dieser Untersuchung verpressten ARBOFORM®-Mischungen aus Lignin, Holzmehl und natürlichen Additiven, die hinsichtlich des Ligningehaltes sowie zum Teil auch der Additivzusätze variierten. Es sollte der Einfluss unterschiedlicher Additivzugaben des kommerziell verfügbaren Produkts auf die Pyrolyseergebnisse untersucht werden. Der Versuch erfolgte im Hinblick auf wesentlich homogenere Materialeigenschaften im Vergleich zum Vollholz und ein weiteres Augenmerk galt der Möglichkeit der Formgebung von ARBOFORM®-Mischungen mittels Spritzguss oder Extrusion. Diese Formgebungsverfahren sind bei ARBOFORM® bereits Stand der Technik und damit wäre es möglich, durch diesen Herstellungsweg komplexe Kohlenstoff- und somit auch Keramikformteile zu ermöglichen, welche durch die herkömmlichen Verfahrenswege nur sehr schwer zu realisieren sind. Durch das vorhandene thermoplastische Prozessfenster bei ARBOFORM® ergeben sich damit weitere Vorteile gegenüber den bereits verwendeten, speziellen Holzwerkstoffen. peerReviewed

A continuous microwave dryer was used for drying wet processed wood fibre based insulating boards. Drying characteristics and energy consumption were compared with convective drying methods. Microwave drying turned out to be faster and facilitates even economical drying of thick boards. peerReviewed

Powder metallurgy is a useful route to forming particulate composite materials; however, the densification of hard and soft powder mixtures is usually inhibited by the more refractory phase. The Bi-W powder compacts were uniaxially pressed at room temperature and the compaction behavior and mechanical properties were evaluated. Pressing was performed in incremental steps from ~1 to 540 MPa. After each step, the pressure was relieved and the thickness and sound-wave transit time were measured in situ (in the die), in order to determine the density and sound-wave velocity in the compact. The data show that the unreinforced Bi powder compacts to ~98 pct density at 540 MPa. The W reinforcement inhibits the densification process, resulting in increased levels of residual porosity. The compaction behavior was evaluated using a modified Heckel equation, while the porosity dependence of the ultrasonically determined elastic modulus was described by a site percolation approach. Postcompaction sound-wave velocity and Vicker’s hardness measurements show

Four field trials were conducted with wood modified with dimethyloldihydroxy-ethyleneurea (DMDHEU) in contact with subterranean termites. Trials 1 to 3 were conducted with Coptotermes acinaciformis (Froggatt); 1 and 2 in south-east Queensland, and 3 in northern Queensland, Australia. Trial 4 was conducted in northern Queensland with Mastotermes darwiniensis (Froggatt). Four timber species (Scots pine, beech, Slash pine and Spotted gum) and two levels (1.3 M and 2.3 M) of DMDHEU were used. The tests were validated. DMDHEU successfully prevented damage by C.acinaciformis in south-east Queensland, but not in northern Queensland. It also did not protect the wood against M.darwiniensis. Except for beech in trial 4, DMDHEU led to reduced mass losses caused by termite attack compared to the unmodified feeder stakes. Slash pine (in trials 1 and 3) and Spotted gum (in trial 1) presented low mass losses. Modification of Scots pine was more effective against termite damage than the modification of beech. peerReviewed

Scots pine (Pinus sylvestris L.) sapwood was treated with quat-silicone micro-emulsion (

In this work, the results of the enzymatic oxidation of TMP-fibers (thermomechanical pulp) and a well-structured lignin model compound, the dehydropolymer (DHP), were investigated by different 14C and 13C methods, caused by a Laccase–Mediator-System (LMS). These methods are the nuclear magnetic resonance spectroscopy (13C-NMR) with DHP (unmarked) and the determination of the 14CO2 release of 14C-marked DHP and TMP-fibers. The 13C-NMR measurements were chosen to analyze the structural changes of the LMS-treated DHP model compounds and TMP-fibers qualitatively and quantitatively. The data of 14CO2 release give an explanation of the demethylation of DHP and TMP-fibers. The effect of the LMS is shown by comparing the results in respect of DHP and TMP-fibers, which were only treated with laccase and of an inactivated LMS as the control. Comparing the results of the 13C-NMR method, in particular the use of the Mediator during the enzymatical treatment, showed significant changes in the structure of the DHP. Also, the TMP-fibers were materially influenced by the LMS. The analysis of the 14CO2 release data of the 14C-marked DHP and TMP-fibers revealed that the rate of 14CO2 increases in the 14C-2 atom as well as in the O14CH3 group within the first hour of Laccase–Mediator incubation. Therefore, the 14CO2 release from the DHP was higher than from the TMP-fibers. peerReviewed

Die Untersuchungen das Kernholzes von Prosopis kuntzei ergaben eine sehr hohe Dauerhaftigkeit gegenüber dem Basidiomyceten Trametes versicolor und der subterranen Termitenart Reticulitermes banyulensis. Im Erdkontakt wird das Holz als mëßig dauerhaft eingestuft. Die niedrigen Masseverluste gegenüber Moderfäule werden neben dem Holzabbau auch Auswaschungsprozessen zugeschrieben. peerReviewed

The study objective was to impart urea-formaldehyde (UF) bonded particleboards higher and longer-lasting hydrophobicity than that resulting from conventionally used paraffin. Alkyl ketene dimer (AKD) is a paper sizing agent that can theoretically esterify wood compounds and result in a surface modification. Particles were 1) impregnated with an aqueous AKD-solution and cured at 130 °C prior to gluing, or 2) sprayed with a mixture of AKD-solution and UF-resin in a single step. Boards with and without paraffin wax were used as controls. Thickness swelling after 2, 24, and 48 h immersion was decreased by 90, 62, and 59% when the chips were impregnated with AKD in comparison to untreated control boards. Water uptake after 2, 24, and 48 h was reduced by 91, 75, and 60%. AKD-impregnation with subsequent curing decreased the internal bond strength by 53%, indicating that AKD impedes the adhesion. The mixture of AKD and UF-glue did not result in considerable hydrophobicity. Increased methyl/methylene and carbonyl bands in FTIR-spectra after toluene-extraction suggest that AKD partially formed ester bonds at the wood surface. Zusammenfassung Das Ziel der Untersuchung bestand darin, Harnstoff-Formaldehyd (UF) gebundene Spanplatten stärker und dauerhafter zu hydrophobieren als es mit konventionell verwendeten Paraffinprodukten möglich ist. Alkylketendimer (AKD) wird in der Papierindustrie als Masseleimungsmittel eingesetzt und kann theoretisch mit Zellwandbestandteilen Esterbindungen eingehen. Holzspäne wurden 1) mit einer wässrigen AKD Lösung imprägniert und bei 130 °C getrocknet oder 2) mit einer AKD/UF-Harz Lösung besprüht. Platten mit und ohne Paraffinbehandlung dienten als Referenzen. Im Vergleich zu Platten ohne Hydrophobierungsmittel wiesen Platten aus AKD-imprägnierten Spänen nach 2-, 24- und 48-stündiger Wasserlagerung eine um 90, 62 und 59% verminderte Dickenquellung auf. Die Wasseraufnahme wurde um 91, 75 und 60% reduziert. Die AKD Imprägnierung führte zu einer Verringerung der Querzugfestigkeit um 53%. Dies deutet darauf hin, dass AKD die Verklebbarkeit negativ beeinflusst. Die Anwendung von AKD im Untermischverfahren führte nur zu geringer Hydrophobierung. FTIR Messungen an Furnierstreifen vor und nach einer Toluolextraktion wiesen darauf hin, dass ein Teil des AKD über Esterbindungen auf der Holzoberfläche fixiert ist. peerReviewed

Scots pine sapwood was treated with glutaraldehyde (GA) in aqueous solution using magnesium chloride as a catalyst in order to evaluate the durability towards weathering. Infrared spectroscopy suggested that GA treatment increased the photo-stability of lignin during artificial weathering of micro-veneers in a QUV over 168 h; photo-protection increased with increasing GA concentration. In comparison with the unmodified controls, GA-modified pine micro-veneer strips exhibited a lower tensile strength loss measured in a zero-span mode in the course of weathering. During 18 months of outdoor exposure, GA-modified pine wood boards exhibited a lower moisture content and water uptake than the unmodified ones. GA treatment also clearly restricted the penetration of blue stain fungi into deeper layers of wood. On the macroscopic scale, the surface of the GA-modified boards was significantly smoother due to less erosion, cracking and minor peeling of tracheids. Scanning electron microscopy further revealed that individual tracheids were detached from the cell compound and then washed away from the unmodified wood surface, whereas tracheids on surfaces of GA-modified wood remained in the tissue compound but displayed many axial and transversal cracks. peerReviewed

The creep rate of Sn solder joints is noticeably affected by joint metallization. Cu|Sn|Cu joints have significantly higher creep rates than Ni|Sn|Cu joints, which, in turn, have higher creep rates than Ni|Sn|Ni joints. Replacing Ni by Cu on both substrates increases the creep rate at 333 K (60 °C) by roughly an order of magnitude. The increased creep rate appears with no apparent change in the dominant creep mechanism; the change in the constitutive equation for creep (the Dorn equation) is in the pre-exponential factor. The decreased creep rate on substituting Ni is accompanied by an increase in the hardness of the polygranular solder but a decrease in the nanohardness of the grain interiors. The source of the strong influence of the Ni substrate appears to be the introduction of an array of Ni3Sn4 intermetallic precipitates along the grain boundaries. These precipitates inhibit grain boundary sliding, boundary reconfiguration, and grain growth during creep. The intermediate creep rate of the asymmetric Ni|Sn|Cu joint has two causes: a decrease in grain boundary mobility due to precipitate decoration and a restriction in the free volume of the joint due to rapid intermetallic growth from the substrate on the Ni side. The sources of this anomalous intermetallic growth are discussed.

The tensile fractures of ultrafine-grained (UFG) Al-Mg alloy with a bimodal grain size were investigated at the micro- and macroscale using transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with focused ion beam (FIB), and optical microscopy. The nanoscale voids and crack behaviors near the tensile fracture surfaces were revealed in various scale ranges and provided the evidence to determine the underlying tensile deformation and fracture mechanisms associated with the bulk bimodal metals. The bimodal grain structures exhibit unusual deformation and fracture mechanisms similar to ductile-phase toughening of brittle materials. The ductile coarse grains in the UFG matrix effectively impede propagation of microcracks, resulting in enhanced ductility and toughness while retaining high strength. In view of the observations collected, we propose a descriptive model for tensile deformation and fracture of bimodal UFG metals.

Sol–gel encapsulation has been used as the basis for detecting cortisol by an immunoassay approach. Previous research showed that antibodies immobilized in the pores of a sol–gel derived silica were able to bind cortisol and be used as an immunosensor. However, this approach was not effective when measuring cortisol levels in human serum because of interference from other fluorescence sources. The present paper describes a protocol which overcomes these limitations and enables sol–gel immunoassays to effectively measure cortisol in human serum over the physiological range of cortisol blood concentrations in an adult (2–28 μg/dL). The method involves a standard additions approach in which various amounts of cortisol are added to the serum. The cortisol concentration values obtained with our sol–gel immunoassay were typically within 10% of the values obtained by traditional analytical methods. The protocol presented here represents a significant contribution to sol–gel sensing and immunoassays in particular, because of the ability to detect an analyte in human serum. In addition, this work reports the first comparison between results from a sol–gel immunosensor and an alternative immuno-binding method for analyte detection.

Acetyliertes, thermisch modifiziertes (TMT) und mit Dimethylol-dihydroxy-ethylenurea (DMDHEU) behandeltes Kiefernholz wurde mit Wachs vollimprägniert. Untersucht wurde der Einfluss hydrophober Wachsdepositen auf die kapillare Wasseraufnahme und die Festigkeiten der bereits modifizierten Hölzer. In longitudinaler Richtung wurde die Wasseraufnahme mit 0,03 kg⋅m−2⋅h−0,5 um das 28fache (Acetylierung) bzw. mit 0,13 kg⋅m−2⋅h−0,5 um das 12fache (TMT) gesenkt. In tangentialer Richtung verringerte sich die Wasseraufnahme mit 0,02 kg⋅m−2⋅h−0,5 um das 9fache (Acetylierung) bzw. mit 0,05 kg⋅m−2⋅h−0,5 um das 12fache (TMT) im Vergleich zu den modifizierten Referenzen. Die Biegefestigkeit von TMT nahm durchschnittlich um 45 %, die Bruchschlagarbeit um 64 % zu. Eine Steigerung der Brinellhärte quer zur Faser um etwa 420 % wurde für TMT erreicht. Eine Reduzierung der mechanischen Eigenschaften, welche durch den Herstellungsprozess von TMT auftreten, wird durch die Vollimprägnierung mit Wachs zum Teil kompensiert. Für acetyliertes Holz bewirkte die Wachsimprägnierung insbesondere einen Anstieg der Druckfestigkeit um 47 % bzw. einen um 66 % erhöhten Biege-Elastizitätsmodul. Die Brinellhärte quer zur Faser erreichte bei der Acetylierung mit ca. 109 N/mm2 die höchsten Werte. Für DMDHEU modifiziertes Holz wurde die Wasseraufnahme um 42 % gesenkt. Die durch die Modifizierung stark herabgesetzte Bruchschlagarbeit erhöhte sich um 45 %. Die Brinellhärte quer zur Faser nahm infolge der Wachsimprägnierung um 150 % zu. Die Wachsimprägnierung führte zu zunehmender Hydrophobierung und Stärkung der durch die jeweilige Modifizierung geschwächten Holzstruktur. peerReviewed

In-situ X-ray diffraction (XRD) measurements using high energy synchrotron radiation were performed to monitor in real time the formation of delta ferrite in a martensitic 9 wt pct chromium steel under simulated weld thermal cycles. Volume fractions of martensite, austenite, and delta ferrite were measured as a function of temperature at a 10 K/s heating rate to 1573 K (1300 °C) and subsequent cooling. At the peak temperature, the delta ferrite concentration rose to 19 pct, of which 17 pct transformed back to austenite on subsequent cooling., Max Kade Foundation, Inc., Austrian Academy of Sciences, United States. Dept. of Energy (Division of Materials Sciences and Engineering, Office of Science, and Office of Basic Energy Sciences)

Specimens of Scots pine sapwood (Pinus sylvestris L.) and beech wood (Fagus sylvatica L.) were treated with an amino-alkyl-functional oligomeric siloxane, a sodium water glass solution and 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU). Treated and untreated wood specimens were exposed outdoors without ground contact. After 9 months of outside exposure, all specimens showed discolouration caused by infestations of mould and staining fungi on the exposed wood surface. Fungi grown on the sample surface were isolated and identified by microscopic technique and sequencing of PCR-amplified DNA from the ITS region. Primarily, an infestation by ascomycetes and related deuteromycetes was found. The most dominant fungi were Trichoderma sp. and Epicoccum sp.. An infestation of Aureobasidium pullulans was only detected on untreated and DMDHEU-treated samples. There were only marginal differences of fungal infestation between the two wood species. peerReviewed

Beech (Fagus sylvatica L.) veneers were treated with two formulations based on N-methylol-melamine (NMM): (1) NMM solution (NMM-1, 10% solid content), (2) fatty acid modified NMM dispersions containing paraffin (with an aluminium salt as catalyst, mNMM-2, 5% solid content). Five veneers were glued with a phenol formaldehyde adhesive to produce plywood. The plywood specimens were weathered outdoors over a period of 18 months according to EN 927-3 (2006). The moisture content of the treated plywood was clearly reduced during the exposure as compared to panels from water treated veneers (controls). As a consequence, the treated plywood displayed higher form stability and less cracks and delamination than the control plywood. Coated, NMM-treated plywood panels displayed remarkable lower degrees of discoloration than the coated controls. These differences between the treated, coated and the coated control panels were not so clearly observed in the case of uncoated panels. The treatment with NMM compounds additionally led to reduced surface colonisation by staining fungi on the indirectly weathered reverse sides of the plywood panels. peerReviewed

Wood was treated with the cationic silica sol (CSS) Levasil 200S and dried at various temperatures (room temperature, 40, 60, 80 and 103 °C). A water leaching test revealed fixation of the silica in wood even after drying at room temperature. Maximum cross sectional swelling of the specimens decreased from 15.6 % (untreated control) to 13.0 %, when treated wood was dried at 103 °C; cell wall bulking values were also negative (−2.3 %), indicating a thermal degradation of the cell wall polymers catalyzed by the CSS. Penetration of the CSS into the cell wall did not occur. A simple flammability test revealed increased fire resistance of the treated wood. Mass loss and velocity of mass loss as well as burning time were reduced; glowing of the formed charcoal was completely prevented. The effectiveness increased with increasing weight percent gain of the CSS in the wood. Thermo gravimetric analysis under nitrogen atmosphere displayed only minor reduction in the initial temperature of thermal decomposition for wood treated with CSS as compared to the control. In the presence of oxygen the resulting charcoal showed comparable thermal behaviour to the control. The yield of charcoal after pyrolysis was increased to a minor extent (from 19.9 to 23.0 %), indicating that the release of combustible gases was hardly reduced. The mode of action of enhanced fire resistance due to CSS-treatment is discussed. peerReviewed