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Scots pine sapwood was acetylated with ethyltriacetoxysilane using acetic acid as a solvent and sulfuric acid as a catalyst. A weight percent gain (WPG) of 14 % and cell wall bulking of 7 % were obtained after 5 h of reaction time. Pine specimens were acetylated with acetic anhydride in the presence of 1 % ethyltriacetoxysilane, dihydroxy-functional siloxane, acetoxy-functional siloxane, amino-functional siloxane and non-functional siloxane, respectively. Acetoxy-functional siloxane induced the greatest reduction in water uptake with a water repellent effectiveness after 24 h of up to 62 % as compared to acetylated wood. WPG and cell wall bulking increased compared to solely acetylated wood with increasing concentrations of acetoxy-functional siloxane in acetic anhydride; anti-shrink efficiency, however, did not increase. Fungal resistance of pine sapwood and beech as well as mechanical strength properties did not change when 20 % acetoxy-functional siloxane was added to acetic anhydride compared to solely acetylated specimens. peerReviewed

The aim of this work was to synthesize and investigate properties of a novel dimethacrylic monomer based on bioderived alicyclic diol--isosorbide. Its potential as a possible substitute of 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (BISGMA), widely used in dental restorative materials and suspected for toxicity was assessed. The novel monomer was obtained in a three-step synthesis. First, isosorbide was etherified by a Williamson nucleophilic substitution and subsequently oxidized to isosorbide diglycidyl ether (ISDGE). A triphenyl phosphine catalyzed addition of methacrylic acid to ISDGE resulted in 2,5-bis(2-hydroxy-3-methacryloyloxypropoxy)- 1,4:3,6-dianhydro-sorbitol (ISDGMA). The monomer obtained was photopolymerized using camphorquinone/2-(dimethylamino)ethyl methacrylate initiating system. Next, compositions with triethylene glycol dimethacrylate (TEGDMA) were prepared and polymerized. Double bond conversion, polymerization shrinkage and water sorption of resulting polymers were determined. Selected mechanical (flexular strength and modulus, Brinell hardness) and thermomechanical (DMA analysis) properties were also investigated. BISGMA based materials were prepared as reference for comparison of particular properties.

Thermisch modifiziertes Holz (TMT) gibt hohe Mengen an Aldehyden (Furfural und Formaldehyd) sowie an flüchtigen organischen Säuren (Ameisen- und Essigsäure) ab. Die Abgabe von Aldehyden und Säuren lässt sich mit Hilfe der Flaschenmethode (EN 717-3) bestimmen. Die Ergebnisse zeigen, dass die Emission an flüchtigen Säuren und Aldehyden durch nachträgliche Ammoniakbehandlung erheblich reduziert wird. Der pH-Wert der Absorptionsflüssigkeit im Flaschenverfahren erhöht sich durch die Ammoniakbehandlung. Dies ist ein Hinweis auf die Abpufferung der Säuren im Holz. peerReviewed

Thermohydrolytic treatment of chips from UF-bonded particleboards using the flask method technique at temperatures of about 103°C resulted in a notable increase in the pH-value of aqueous absorption medium after a reaction period of 24 h, most likely due to degradation of the UF-resin. This leads to neutralisation of the stronger formic acid to a much higher extent than acetic acid. Accordingly, the release of formic acid using the flask technique decreases to a much higher extent compared to that of acetic acid under the same conditions. The release of acetic acid could also be enhanced by possible deacetylation of the wood material induced by the hardener usually present in recovered UF-boards. This indicates that inextricably intertwined reactions unfold on hydrothermic degradation of UF-bonded particleboards. peerReviewed

Rotary cut 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 treated veneers were bonded with phenol formaldehyde (PF) adhesive to produce plywood in two different processes. peerReviewed

The correction factor developed by Jann and Deppe (1990) to adjust the measured perforator values of particleboards and fibreboards measured at different moisture contents in the range of 3% ≤ u ≤ 9% to the level at 6.5% moisture content has two main deficiencies. It takes no account of the influence of the molar ratio of the resins used, which seems to remarkably impact the relationship between the moisture content and the measured perforator values. Moreover, research work revealed that the correction factor to be applied also depends on the moisture content, at which the perforator value was measured, according to an inversely proportional correlation. Besides, the correction factor according to Jann–Deppe leaves this fact unconsidered. peerReviewed

International audience; Buchenholz wurde mit heiß schmelzendem Wachs imprägniert. Durch Kontaktwinkelmessungen wurde der hydrophobe Charakter des imprägnierten Holzes quantifiziert. Mit Zugscherversuchen wurden die Verklebungsgüte nach verschiedenen Lagerungsfolgen geprüft. Wachsimprägnierte Buche wurde einer Plasmabehandlung unterzogen und ihre Wirkung auf die Verklebungsgüte untersucht. Das unpolare Paraffin zeigte schlechtere Verklebungsresultate als das Montanesterwachs, so dass ein primärer Einfluss des verwendeten Wachstyps auf die Verklebung des imprägnierten Holzes deutlich wird. Eine Verklebung imprägnierter Buche mit Montanesterwachs ist im Innenbereich für konstruktive Holzbauteile möglich. Unter dauerfeuchten Bedingungen werden durch konventionelle, mit Härtern versehene Polyvinylacetat-Leime und Phenol-Resorcinol-Harz D3 Eigenschaften im nichtkonstruktiven Bereich erreicht. Die Plasmabehandlung verbessert diese Verklebungseigenschaften auf D4. Im wechselfeuchten Umgebungsbereich bewährten sich Isocyanatkleber und nach einer Plasmabehandlung von 120 s Polyvinylacetat-Leim.

In this study, the impact of a plasma treatment using dielectric barrier discharge at atmospheric pressure on wax-treated beech was investigated by surface energy determination and adhesion tests. Measurements of the surface energy revealed a strong increase in surface polarity along with increased surface energy as a result of the plasma treatment, pointing to increased adhesion properties. To evaluate the adhesion properties of a polyvinyl acetate (PVAc) adhesive on beech treated with montan ester wax and synthetic Fischer–Tropsch wax, a special peel test was applied. This peel test provided evidence of increased adhesion of the PVAc after plasma treatment of both materials investigated. peerReviewed

The aim of this study was to use energy-dispersive X-ray spectroscopy (EDX) to localize chitosan in the cell wall of chitosan-impregnated Scots pine. It was of interest to investigate the concentration of chitosan in wood to gain further knowledge and understanding of the distribution of chitosan in the wooden matrix. After deacetylation, chitosan was re-acetylated with chloroacetic anhydride to achieve a covalent bonding of chloride to the chitosan polymer. Chloride-labelled chitosan was measured by EDX using a scanning electron microscope and described as chloride intensity. Analysis of free chloride anions was performed by dialysis and inductively coupled plasma atomic emission spectroscopy. There was a significant correlation between the molecular weight of chitosan and the intensity of covalent-bonded chloride to the chitosan polymer. High molecular weight chitosan showed a better interaction with the cell wall structure than low molecular chitosan. peerReviewed

The dynamic water vapour sorption properties of Scots pine (Pinus sylvestris L.) wood samples were studied to investigate the modifying effects of glutaraldehyde. Pine sapwood was treated with solutions of glutaraldehyde and a catalyst (magnesium chloride) to obtain weight per cent gains of 0.5, 8.6, 15.5, and 21.0%, respectively. The sorption behaviour of untreated and treated wood was measured using a Dynamic Vapour Sorption apparatus. The results showed considerable reduction in equilibrium moisture content of wood and the corresponding equilibrium time at each target relative humidity (RH) due to glutaraldehyde treatment. The moisture adsorption and desorption rates of modified and unmodified wood were generally faster in the low RH range (up to approximate 20%) than in the high range. Modification primarily reduced the adsorption and desorption rates over the high RH range of 20–95%. Glutaraldehyde modification resulted in a reduction in sorption hysteresis due to the loss of elasticity of cell walls. peerReviewed

As a result of recent investigations on nanocrystalline (nc) materials, extensive experimental data on the deformation behavior of these materials have become available. In this article, an analysis of these data was performed to identify the requirements that a viable deformation mechanism should meet in terms of accounting for the mechanical characteristics and trends that are revealed by the data. The results of the analysis show that a viable deformation mechanism is required to account for the following: (1) an activation volume the value of which is in the range 10 to 40 b 3; (2) an activation energy that is close to the activation energy for boundary diffusion but that decreases with increasing applied stress; (3) the magnitudes of deformation rates that cover wide ranges of temperatures, stresses, and grain sizes; (4) inverse Hall–Petch behavior; and (5) limited ductility. The validity of available deformation mechanisms for nc materials is closely examined in the light of these requirements.

The synthesis of bulk ultrafine-grained (UFG) and nanostructured Al via cryomilling can frequently require a degassing step prior to consolidation, partly due to the large surface area of the as-milled powders. The objective of this study is to investigate the effects associated with cryomilling with stearic acid additions (as a process-control agent) on the degassing behavior of Al powders. This objective was accomplished by completing select experiments with Al-7.5Mg, Al-6.4 wt pct Al85Ni10La5, and Al-14.3 wt pct B4C. The interaction between Al and stearic acid was determined using thermal analysis combined with Fourier transform infrared spectroscopy (FTIR). The degassing experiments were carried out under high vacuum (10−4 to ~10−6 torr) in a range from room temperature to 400 °C, with the pressure of the released gases monitored using a digital vacuum gage. The results showed that the liberation of chemisorbed water was suppressed in cryomilled Al powders and both the chemisorbed water and stearic acid were primarily released in the form of hydrogen. It was also demonstrated that under certain conditions, a nanostructure (grain size ~100 nm) can be retained following the hot vacuum degassing of cryomilled Al.

The cyclic deformation behavior of cryomilled (CM) AA5083 alloys was compared to that of conventional AA5083-H131. The materials studied were a 100 pct CM alloy with a Gaussian grain size average of 315 nm and an alloy created by mixing 85 pct CM powder with 15 pct unmilled powder before consolidation to fabricate a plate with a bimodal grain size distribution with peak averages at 240 nm and 1.8 μm. Although the ultra-fine-grain (UFG) alloys exhibited considerably higher tensile strengths than those of the conventional material, the results from plastic-strain-controlled low-cycle fatigue tests demonstrate that all three materials exhibit identical fatigue lives across a range of plastic strain amplitudes. The CM materials exhibited softening during the first cycle, similar to other alloys produced by conventional powder metallurgy, followed by continual hardening to saturation before failure. The results reported in this study show that fatigue deformation in the CM material is accompanied by slight grain growth, pinning of dislocations at the grain boundaries, and grain rotation to produce macroscopic slip bands that localize strain, creating a single dominant fatigue crack. In contrast, the conventional alloy exhibits a cell structure and more diffuse fatigue damage accumulation.

The effect of raw material, adhesive and climatic conditions on the surface roughness and moisture content of uncoated particleboards was determined. Particleboards made with recycled particles in the surface layer had the roughest surfaces irrespective of the adhesive used. The relationship between equilibrium moisture content and roughness are a complex function of interactions between many variables. peerReviewed

Alkyl ketene dimer (AKD) was used as a hydrophobic agent for PF-bonded particleboards. In contrast to conventionally used paraffin, AKD can be covalently bonded to the chip surface by esterification with wood hydroxyl groups. FTIR analyses before and after toluene extractions indicated that only a small amount of the applied AKD is chemically bonded. Wettability studies on veneer strips suggested that particularly the bonded AKD accounts for the surface hydrophobicity. peerReviewed

The fabrication of dense coatings with appropriate properties using a high velocity oxygen fuel (HVOF) spray process requires an in-depth understanding of the complete gas flow field and particle behavior during the process. A computational fluid dynamics (CFD) model is implemented to investigate the gas flow behavior that occurs during the HVOF process and a simplified one-dimensional decoupled model of the in-flight thermal behavior of the amorphous Fe-based powder particles was developed and applied for three different spray conditions. The numerical results were used to rationalize the different coating microstructures described in the experimental results. Low porosity and amorphous coatings were produced using two different particle size distributions (16 to 25 μm and 25 to 53 μm). The amorphous characteristics of the powder were retained in the coating due to melting and rapid solidification in the case of very fine powder or ligaments (

In this article, the laser-engineered net shaping (LENS) process is implemented to fabricate net-shaped Fe-based Fe-B-Cr-C-Mn-Mo-W-Zr metallic glass (MG) components. The glass-forming ability (GFA), glass transition, crystallization behavior, and mechanical properties of the glassy alloy are analyzed to provide fundamental insights into the underlying physical mechanisms. The microstructures of various LENS-processed component geometries are characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The results reveal that the as-processed microstructure consists of nanocrystalline α-Fe particles embedded in an amorphous matrix. An amorphous microstructure is observed in deposited layers that are located near the substrate. From a microstructure standpoint, the fraction of crystalline phases increases with the increasing number of deposited layers, effectively resulting in the formation of a functionally graded microstructure with in-situ-precipitated particles in an MG matrix. The microhardness of LENS-processed Fe-based MG components has a high value of 9.52 GPa.

Scots pine (Pinus sylvestris L.) samples were vacuum pressure impregnated with quaternary ammonium (quat)-silicone micro-emulsion (

Zusammenfassung Die Abgabe an flüchtigen Säuren von UF-Harz gebundenen Kiefernholzspanplatten wurde nach der Herstellung sowie nach einer Alterungsdauer von 13 Jahren bestimmt. Die Ergebnisse lassen erkennen, dass die Abgabe an Ameisensäure durch die Alterung der Platten deutlich abgenommen hat, während die Abgabe an Essigsäure signifikant zugenommen hat. Auf diesen Zusammenhang scheint der bei der Plattenherstellung verwendete Härtertyp (Ammoniumnitrat, Ammoniumchlorid) und die eingesetzte Härtermenge keinen entscheidenden Einfluss zu nehmen. The release of volatile organic acids from UF-bonded particleboards made from Scots pine was assessed after production as well as after aging for 13 years. The results reveal that aging significantly decreased the release of formic acid and substantially increased the emanation of acetic acid. The change in the release of volatile acids by aging seems to be highly independent of the hardener type used (ammonium chloride, ammonium nitrate) as well as of the amount of added hardener. peerReviewed

Wood-based panels release different amounts of volatile organic acids, which depend, among other factors, on the binder used. The volatile acids released from the boards can be measured using the flask method following the principle of measuring the formaldehyde release according to EN 717-3. Particleboards bonded with alkaline curing phenol-formaldehyde resins (PF-boards) release higher amounts of acetic and lower amounts of formic acid compared to those boards bonded by acid curing urea-formaldehyde reins (UF-resins) or binders based on polymeric diphenylemethandiisocyanates (PMDI). This has been explained by the equilibrium reaction between sodium hydroxide in PF-resins and volatile acids, which leaves less free formic acid than free acetic acid to emanate from the boards. Increasing the binder content in the boards also leads to an increase in the over all amount of sodium hydroxide in the boards. Accordingly, less free acids are left, which could be released from the boards. Fibres made by the chemo-thermo-mechanical process (CTMP) using sodium hydroxide and sodium sulphite as pulping agents release less formic acid than those made by the thermo-mechanical pulping (TMP). This behaviour was also attributed to the equilibrium reaction between the alkali in CTMP-boards and the volatile acids. Zusammenfassung Holzwerkstoffe geben u. a. in Abhängigkeit von dem verwendeten Bindemittel unterschiedliche Mengen an Ameisen- und Essigsäure ab, die nach dem Prinzip der Flaschenmethode in Anlehnung an die Vorgehensweise bei der Bestimmung der Formaldehydabgabe nach EN 717-3 bestimmt werden können. Mit alkalisch härtenden Phenolformaldehydharzen hergestellte Holzspanplatten (PF-Platten) geben weitaus mehr Essigsäure und viel weniger Ameisensäure ab als jene die mit Säure härtenden Harnstoffformaldehydharzen (UF-Harze) oder mit Klebstoffen auf Basis von polymeren Diphenylmethandiisocyanaten (PMDI) hergestellt wurden. Dies wird damit erklärt, dass es zwischen dem Alkali in PF-Spanplatten und den flüchtigen Säuren zu Gleichgewichtsreaktionen kommt, bei denen mehr Formiationen als Acetationen im Gleichgewicht sind. Eine Erhöhung des Bindemittelanteils in PF-Spanplatten verringert die Abgabe von Essig- und Ameisensäure, da hierdurch zwangsläufig die Alkalimenge in den Platten erhöht wird, die die Bildung von Formiat- und Acetationen forciert. Auch aus den Fasern, die nach dem chemo-thermo-mechanischen Prozess (CTMP) hergestellt wurden, entweicht mehr Essigsäure und weniger Ameisensäure als aus den Fasern, die nach dem thermo-mechanischen Prozess (TMP) hergestellt sind. Dies wird auch durch die Gleichgewichtsreaktion zwischen dem Alkali und den flüchtigen Säuren erklärt. peerReviewed

Thermal modification of wood (ash, beech, spruce) leads to a remarkable decrease in the Water Retention Value (WRV). In case of beech wood the WRV-value decreased after immersion in water for 72 h from 55.5% to 40.5% (about 27%) and in case of spruce wood from 49.3% to 34.5% (about 30%). The decrease in the WRV of ash wood was relatively low (about 19%). The WRV-method seems to be useful to follow up the process of thermal modification of wood. peerReviewed

Zusammenfassung IR-spectra of TMP and CTMP prepared from pine wood and UF-bonded MDF made from pine wood show characteristic differences. The typical band for carbonyl groups (C=O-groups) at wave number about 1740 cm-1 is strong in pine wood, but appears relatively weak in TMP and especially in CTMP made thereof. In UF-bonded MDF made from pine wood the band at about 1740 cm-1 is very weak compared to that in pine wood. Moreover, no significant difference in the IR-spectrum between TMP and CTMP made from UF-bonded MDF seems to exist. This is attributed to the fact that during thermo-mechanical pulping of UF-bonded boards hydrolytic degradation of the resin takes place enhancing the formation of ammonia which increases the pH-value of the fibres and leads therefore to chemo-thermo-mechanical pulping. peerReviewed

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 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