Influence of thermal pretreatments on dimensional change and humidity sensitivity of densified spruce and poplar wood

The effect of thermal pretreatments on the dimensional change and humidity sensitivity of densified spruce (Picea orientalis) and poplar (Populus nigra) wood were investigated. A thermal pretreatment was applied on the wood specimens at 140 °C, 160 °C, 180 °C, and 200 °C for 7 h and 9 h. Wood specimens were then compressed at ratios of 20 % and 40 % at a temperature of 150 °C. The results showed that spring-back and thickness swelling increased in all specimens (thermally pre-treated and untreated) depending on the increase in compression ratio. However, set-recovery was determined higher at 20 % compression ratio. The equilibrium moisture content values ​​of untreated specimens and thermally pre-treated specimens at low temperatures (140 ºC and 160 ºC) were found lower than uncompressed specimens. The impact of compression ratio on equilibrium moisture content was not clear. Thermal pretreatments significantly affected the dimensional stability and hygroscopicity of densified specimens (especially poplar wood). Depending on the increase in thermal pretreatment temperature and duration, spring-back, set-recovery and thickness swelling in wood specimens decreased up to 31 %, 67 % and 62 %, respectively. In addition, equilibrium moisture content and water absorption decreased with the increase in thermal pretreatment temperature and duration. Moreover, the thermal treatment temperature was more important than duration on the investigated properties

Otpornost borovine i bukovine impregnirane ekstraktima biljaka R. luteum i R. ponticum na propadanje i promjenu boje

In this study, the effect of impregnation with natural extracts on decay resistance and color change of pine and beech wood was analyzed. Flowers of Rhododendron luteum and Rhododendron ponticum plants were extracted according to the decoction method and aqueous solutions were prepared at different concentration levels (2 %, 4 % and 7 %). In addition, ferrous sulfate, copper sulfate and aluminum sulfate mordants were added to the solution to improve the properties of the extracts. Then the wood specimens were impregnated with the prepared solutions. The results indicated that the effect of plant species on the mass loss of specimens exposed to T. versicolor (white-rot fungus) was insignificant. Non-mordant extracts had a slight effect on the mass loss of the specimens. However, in pine and beech specimens impregnated with mordant-added (especially ferrous sulfate-added) extracts, mass loss was significantly reduced and resistance to fungal rot was almost completely achieved. The concentration level did not have a significant effect on the mass loss of specimens treated with mordant-added extracts. After impregnation, the L* value of all specimens (especially those treated with ferrous sulfate-added extracts) decreased and the specimens darkened. The a* and b* values increased in specimens treated with non-mordant and aluminum sulfate-added extracts and these specimens tend to have a red-yellow color. The a* value decreased and the b* value increased in wood specimens treated with copper sulfate-added extracts. The green-yellow color trend of these specimens increased. Both the a* and b* values of the specimens treated with ferrous sulfate-added extracts decreased and the green-blue color tendency increased in these specimens. The increase in the concentration level positively affected the determined color changes. The total color change (ΔE*) was higher in wood specimens (especially pine) treated with ferrous sulfate-added R. ponticum extracts.U istraživanju je analiziran utjecaj impregnacije borovine i bukovine biljnim ekstraktima na otpornost na propadanje. Cvjetovi biljaka Rhododendron luteum i Rhododendron ponticum ekstrahirani su metodom dekocije te su pripremljene vodene otopine različitih koncentracija (2 %, 4 % i 7 %). Osim toga, otopini su dodani fiksatori željezov sulfat, bakrov sulfat i aluminijev sulfat radi poboljšanja svojstava ekstrakata. Zatim su uzorci uzoraka izloženih djelovanju T. versicolor (gljivi bijele truleži) bio neznatan. Ekstrakti bez fiksatora imali su mali učinak na gubitak mase uzoraka. Međutim, znatno je smanjen gubitak mase uzoraka borovine i bukovine impregniranih ekstraktima s dodatkom fiksatora (osobito željezova sulfata), a postignuta je gotovo potpuna otpornost na gljive truležnice. Koncentracija otopine nije imala znatniji utjecaj na gubitak mase uzoraka zaštićenih ekstraktima s dodatkom fiksatora. Nakon impregnacije smanjila se L* vrijednost svih uzoraka (posebno onih zaštićenih ekstraktima s dodatkom željezova sulfata) i uzorci su potamnjeli. Povećale su se vrijednosti a* i b* uzoraka impregniranih ekstraktima bez dodatka fiksatora i ekstraktima s dodatkom aluminijeva sulfata i ti su uzorci poprimili crvenožutu boju. Vrijednost a* uzoraka drva premazanih ekstraktima s dodatkom bakrova sulfata smanjila se, a vrijednost b* se povećala. Udio žutozelene komponente na tim se uzorcima povećao. Vrijednosti a* i b* uzoraka premazanih ekstraktima s dodatkom željezova sulfata smanjile su se i povećao se udio zelenoplave komponente. Povećanje koncentracije otopine kojom su uzorci impregnirani pozitivno je utjecalo na promjenu boje. Ukupna promjena boje (ΔE*) bila je veća na uzorcima drva (osobito borovim) impregniranim ekstraktima R. ponticum s dodatkom željezova sulfata

Utjecaj vodoodbojnih sredstava na higroskopnost i dimenzijsku stabilnost ugušćenog drva jele i drva jasike

This study investigated the effect of pre-impregnation with water-repellent agents on the hygroscopicity and dimensional stability of fir (Abies bornmulleriana Mattf.) and aspen (Populus tremula L.) woods. After pre-vacuum treatment, the samples were impregnated at atmospheric pressure with paraffin, linseed oil and styrene, and then densified at compression rates of 20 % and 40 % at 120, 150 and 180 °C. The results showed that water repellents significantly affected the hygroscopicity and dimensional stability of the densified wood samples. Compression recovery rate (CRR), thickness swelling (TS), equilibrium moisture content (EMC), and water absorption (WA) values of the densified samples decreased with impregnation pretreatments. The linseed oil treatment gave more positive CRR and TS results than paraffin. Lower EMC and WA values were found in the paraffin-treated samples. However, the most successful results for all tested properties were determined in the styrene pretreated samples in which hygroscopicity decreased and dimensional stability increased (especially for aspen) due to increases in the compression rate and temperature related to densification conditions. In the styrene pretreated samples, the high temperature (180 °C) and compression rate (40 %) significantly reduced CRR, TS, EMC and WA, total dimensional stability was nearly achieved and the water repellent effectiveness was close to 100 %.U radu se prikazuje istraživanje utjecaja predimpregnacije drva jele (Abies bornmulleriana Mattf.) i jasike (Populus tremula L.) vodoodbojnim sredstvima na njihovu higroskopnost i dimenzijsku stabilnost. Nakon vakuumske obrade uzorci su pri atmosferskom tlaku impregnirani parafinom, lanenim uljem i stirenom. Zatim je provedeno ugušćivanje sa stupnjevima ugušćenja 20 i 40 % pri temperaturi od 120, 150 i 180 °C. Rezultati su pokazali da vodoodbojna sredstva značajno utječu na higroskopnost i dimenzijsku stabilnost uzoraka ugušćenog drva. Predimpregnacijom uzoraka smanjili su se stupanj povrata ugušćenja (CRR), debljinsko bubrenje (TS), ravnotežni sadržaj vode (EMC) i apsorpcija vode (WA) ugušćenih uzoraka. Postupkom s lanenim uljem smanjeni su povrat ugušćenja i debljinsko bubrenje u usporedbi s postupkom impregnacije parafinom. Na uzorcima impregniranim parafinom utvrđene su niže vrijednosti ravnotežnog sadržaja vode i apsorpcije vode. Međutim, najbolji rezultati svih istraživanih svojstava dobiveni su na uzorcima impregniranima stirenom, kojima se zbog povećanja brzine i temperature ugušćivanja smanjila higroskopnost i povećala dimenzijska stabilnost (posebice drva jasike). Na uzorcima impregniranima stirenom i ugušćenima pri temperaturi od 180 °C sa stupnjem ugušćenja 40 % znatno su se smanjili stupanj povrata ugušćenja, debljinsko bubrenje, ravnotežni sadržaj vode i apsorpcija vode te je postignuta gotovo potpuna dimenzijska stabilnost i učinkovitost odbijanja vode (blizu 100 %)

Density, hardness and strength properties of densified fir and aspen woods pretreated with water repellents

In this study, the effect of thermo-mechanical densification on the density, hardness, compression strength, bending strength (MOR), and modulus of elasticity (MOE) of fir and aspen wood pretreated with water repellents was analyzed. Wood specimens were impregnated with paraffin, linseed oil and styrene after prevacuum treatment. Then, the impregnated wood specimens were densified with compression ratios of 20 and 40%, and at 120, 150 and 180 degrees C. The results indicated that the density, hardness and strength properties of the all densified specimens (untreated and impregnated) increased depending on the compression ratio and temperature. For all tested properties, higher increases were obtained in the paraffin and styrene pretreated specimens compared to untreated samples. However, the increase rates in linseed oil pretreated specimens were generally lower than untreated specimens. Regarding water repellents the most successful results in all tested properties were determined in styrene pretreated specimens. The density, hardness and strength properties of all specimens increased with the increase in compression ratio. On the other hand, the increase in the compression temperature negatively affects the properties of untreated and linseed oil pretreated specimens, while having a generally positive effect on the properties of paraffin pretreated specimens. However, all tested properties of styrene pretreated specimens have increased significantly due to the increase in compression temperature. The increasing strength properties of wood as a result of densification have increased much more with paraffin and especially styrene pretreatment. These combinations can be considered as an important potential for applications that require more hardness and strength.Research Fund of Duzce UniversityDuzce University [BAP2017.07.01.522]The authors are grateful for the support of the Research Fund of Duzce University, grant no. BAP2017.07.01.522.WOS:0006367392000052-s2.0-8509201257

Roughness, Wettability, and Morphological Properties of Impregnated and Densified Wood Materials

The effects of pre-impregnation on surface roughness, wettability, and morphological structure of densified aspen and fir wood were investigated. Wood specimens were impregnated with paraffin, linseed oil, and styrene after pre-vacuum treatment. The impregnated specimens were densified using compression ratios of 20% and 40% at 120 °C, 150 °C, and 180 °C. The roughness decreased and the contact angle increased in all impregnated specimens (undensified and densified). Compared to paraffin and linseed oil-impregnated specimens, lower roughness and higher contact angle were found in styrene-impregnated specimens. After densification, the roughness and wettability of the wood specimens decreased. More successful results (lower roughness and higher contact angle) were generally obtained in specimens densified with high compression ratio (40%). In both untreated and impregnated specimens, the contact angle increased with increasing compression temperature. While the effect of compression temperature on the roughness of the fir specimens was not significant, the roughness of the aspen specimens (especially styrene-impregnated) decreased with the increase in temperature. Scanning electron microscopy observations indicated that impregnation agents (especially styrene) clung to wood cell walls and partially or completely filled the lumens. This was positively correlated with the determined roughness and wettability. Pre-impregnation facilitated wood densification without significant cell deformations

Influence of Processing Parameters on the Surface Roughness of Solid Wood Cut by Abrasive Water Jet

The surface roughness of pine, beech, and oak wood cut in the abrasive water jet (AWJ) system was evaluated for different processing parameters. Wood specimens were prepared in thicknesses of 18, 36, and 54 mm in both tangential and radial directions. Then the specimens were cut, applying three different feed speeds (50, 100, and 200 mm/min), three different abrasive flow rates (200, 300, and 450 g/min), and two different cutting liquid pressures (300 and 380 MPa) with the AWJ system. The R-a and R-Z roughness values were higher in the tangential cut for pine and oak specimens and in the radial cut for beech wood. Roughness values increased in all specimens with increases in the AWJ feed speed and the wood thickness. In contrast, with increased amounts of abrasive, R-a and R-Z values of the specimens decreased and surface smoothness tended to increase. Roughness values of pine and oak specimens generally decreased due to the increase in liquid pressure. However, an increase in the roughness of the beech specimens was determined. As a result, the feed speed and wood thickness were the most influential parameters on the roughness of specimens. In contrast, the cutting direction and liquid pressure showed less importance on the roughness.Research Fund of Duzce UniversityDuzce University [BAP-2017.07.01.521]The authors are grateful for the support of the Research Fund of Duzce University, Grant No. BAP-2017.07.01.521.WOS:0005557911000062-s2.0-8508845193

Surface Roughness of Thermally Treated Wood Cut with Different Parameters in CNC Router Machine

The effects of different machining parameters on surface roughness values of thermally treated pine, beech, and linden woods cut in a computer numerical control (CNC) router machine were examined. Wood specimens were thermally treated at 170, 190, and 210 degrees C for 2 h. Then, specimens were cut in the radial and tangential directions with three different spindle speeds (12000, 15000, and 18000 rpm) and three different feed rates (3000, 4000, and 6000 mm/min) using two different end mill tools (spiral and straight) on the CNC machine. The end mill type significantly affected the roughness values of the untreated and thermally treated specimens in both directions. Lower roughness values were found in the specimens (especially pine) machined with the straight end mill compared to those machined with the spiral end mill. Roughness generally decreased in the thermally treated specimens. However, thermal treatment temperature did not have a notable effect on roughness. As the spindle speed increased, the roughness values of all specimens decreased. In contrast, as the feed rate increased, the roughness values increased. Therefore, the end mill type, feed rate, and spindle speed were the most influential parameters on the roughness.Research Fund of Duzce UniversityDuzce University [BAP-2018.07.01.742]The authors are grateful for the support of the Research Fund of Duzce University, Grant No. BAP-2018.07.01.742.WOS:00068834260002

Effects of Heat Post-Treatment on Dimensional Stability and Water Absorption Behaviours of Mechanically Densified Uludag Fir and Black Poplar Woods

One of the most persistent problems with mechanically densified wood is its inherent dimensional instability. The effects of heat post-treatment on the changes in spring-back (SB), compression ratio recovery (CRR), thickness swelling (TS), and water absorption (WA) of newly-tested Uludag fir (Abies bornmuelleriana Mattf.) and black poplar (Populus nigra L.) wood samples that had been thermo-mechanically densified were investigated. Samples were densified with compression ratios of 25\% and 50\% with temperatures of 100 and 140 degrees C, respectively. Then, the heat post-treatment was applied to the samples at 185 and 212 degrees C for 2 h. For the two newly-tested wood types, results of the preliminary study show that SB and TS were higher at a 50\% compression ratio compared with 25\%. Regarding densification temperature, TS was lower in samples densified at 140 degrees C, while SB was higher. WA values were lower in compressed samples (50\%) at high rates. The effect of the densification temperature on WA was insignificant. Heat post-treatment had a considerable effect on the dimensional stability and hygroscopicity of the densified Uludag fir and black poplar samples. With an increase in heat treatment temperature, the dimensional stability increased, while the hygroscopicity of densified samples decreased. As a result of heat post-treatment applied at 212 degrees C, SB, CRR, TS, and WA decreased by 88\%, 85\%, 79\%, and 53\%, respectively

Effects of Thermomechanical Densification and Heat Treatment on Density and Brinell Hardness of Scots Pine (Pinus sylvestris L.) and Eastern Beech (Fagus orientalis L.)

The effects of thermomechanical densification (TMD) and heat treatment on density and Brinell hardness of Scots pine (Pinus sylvestris L.) and Eastern beech (Fagus orientalis L.) woods were investigated. Samples were densified using a specially designed hydraulic press with target compression ratios of 20 and 40\%, and at 110 degrees C and 150 degrees C. Then, the heat treatment was applied to the samples at three different temperatures. To determine whether the changes occurred because of technological properties, tests of Brinell hardness and air-dry density were conducted. Increases of 42 and 35\% were obtained for the density of Scots pine and beech samples, respectively. After the densification process, increases in radial and tangential hardness values were obtained. Decreases were observed in the density and hardness values of the samples because of the increase in temperature during heat treatment. After heat treatment, there were 4 and 5\% decreases in the respective densities of Scots pine and beech, and decreases in their radial and tangential hardness values

The Effects of Densification and Heat Post-Treatment on Hardness and Morphological Properties of Wood Materials

This study investigated the effects of densification and heat post-treatment on the Janka hardness and microscopic structure of relatively low-density Uludag fir, linden, and black poplar woods. Wood samples were densified with compression ratios of 25\% and 50\% at 100 degrees C and 140 degrees C, respectively. Heat post-treatment was then applied to the samples at 185 degrees C and 212 degrees C for 2 h. The hardness in the radial and tangential directions was determined, and morphological changes in the cell structures were analyzed using scanning electron microscopy (SEM). The hardness values in the radial and tangential directions of the densified samples increased depending on the compression rate and treatment temperature. The hardness values in both directions were higher in the 50\% compressed samples. For samples compressed at 140 degrees C, the hardness values were higher in the tangential direction, whereas the samples compressed at 100 degrees C were higher in the radial direction. After the heat post-treatment process, the hardness values of all samples decreased. As the treatment temperature increased, more adverse effects on the hardness was noted. According to the SEM analyses, the densification and heat post-treatment deteriorated the cell structure of the samples. The more cell deformation was observed in the samples densified at 100 degrees C with compression ratio 50\% and high heat post-treatment temperature