This study focuses on manufacturing of medium density fibreboard (MDF) panels bonded with dextrin-based wood adhesive and crosslinked in situ with various weight ratios of synthetic (e.g., polymeric-methane diphenyl-diisocyanate, pMDI) or bio-based (e.g., glyoxal) crosslinkers. The physical and mechanical properties of the panels were evaluated and compared with those from panels without crosslinker (control). Modulus of rupture (MOR) and internal bond (IB) strength of the MDF panels were considerably increased by increasing the crosslinkers’ content. While, slight improvements were observed in modulus of elasticity (MOE) of the panels as a function of crosslinker type and content. Addition of crosslinkers clearly reduced the thickness swelling (TS) and water absorption (WA) of the panels, whereas, the panels with pMDI showed superior performances than the control and glyoxal added ones within 4 h and 24 h immersion in water. The results indicate the potential of dextrin as wood panel adhesive along with the use of appropriate crosslinkers.
Palmyra palm (Borassus aethiopum Mart.) is a large palm tree whose wood is often used for its mechanical resistance and weathering in buildings in Africa. In this work, the influence of fibre characteristics on the mechanical properties of wood was studied. For this purpose, the mechanical characteristics were determined and study of the micrograph of the sapwood and Duramen which are the useful parts of this wood were carried out. The results of this study show the mechanical properties of the palmyra are very influenced by the number and the mechanical characteristics of the fibres. The proposed polynomial model of the evolution of the mechanical characteristics gives the good results because the maximum relative mistakes of the prevision are 4.43% for the breaking strength and 0.40% for the Young’s modulus.
Experimental material was obtained from 43 trees of four tree species, namely pine, fir, larch and spruce from the territory of Slovakia. Wood and bark samples were taken from the discs in three locations on a stem and from small-wood, branches coming from tree crowns. The volume of fresh samples was measured in calibrated graduated cylinders with a precision of 1 ml; a dry matter was measured with a precision of 0.01 g. The statistically significant effect has been shown in tree species, fractions of biomass and locations on the tree using a special software based on ANOVA. The average basic density of wood for all species ranges from 373 to 508 kg. m-3. For bark it is 333-551 kg. m-3 and for small-wood outside bark it reaches 406-535 kg. m-3. The fir and larch have the lowest and highest values for wood density; pine and fir for bark density and pine and spruce species for small-wood density.
In this study, cyclic tests were performed on the larch CLT shear walls depending on the half lap reinforcement of half-lap connections and reinforced plywood of spline connections in order to evaluate the horizontal shear performance of the larch CLT walls. The test results show that there is no difference in residual strength depending on the reinforcement of half-lap connection, but their initial stiffness has been increased by 9%. There was no significant difference either in the residual strength of double spline connections depending on the application of reinforced plywood, while the spline reinforcement has failed to increase initial stiffness. All of the larch CLT walls constructed according to the edge connection shape were measured to have a strength reduction ratio of less than 10% in each horizontal displacement intervals and an equivalent viscous damping ratio of less than 10% for energy dissipation in the initial and final horizontal displacement intervals, thereby confirming that their excellent horizontal shear performance and seismic performance.
Four specimens of a thin-walled square steel tube/bamboo plywood composite hollow column with binding bars (SBCCB) were each subjected to an axial compressive creep test and a subsequent axial compression test to examine their axial compressive creep behavior and post-creep compressive failure modes as well as to analyze the effects of long-term loading on the ultimate axial compression-bearing capacity of the SBCCB. The results show that the axial compressive creep strain decreased with increasing slenderness ratio and increased with increasing axial compressive stress. The creep–time curves of the specimens with various slenderness ratios all exhibited a transient creep stage and a steady-stage stage. Temperature and humidity variations affected local creep behavior. Creep significantly affected the axial compression-bearing capacity as well as the axial and lateral deformability of the SBCCB. The rheological mechanics-based Burgers model can well predict the creep strain development of the SBCCB.
This study was designed to determine some selected parameters such as gloss, surface roughness, and color changes of Scots pine wood impregnated with commonly used fireretardant (FR) chemicals after UV irradiance. Sodium acetate (SA), ammonium chlorite (AC), zinc chlorite (ZC), ammoniumsulphate (AS), and di ammonium phosphate (DAP) were used as fire retardants. Wood specimens were prepared from Scots pine (Pinus sylvestris L.). Before test, wood specimens were impregnated with 5 % aqueous solution of chemicals according to ASTM D 1413-76 standard. Results showed that UV irradiance caused gloss loss and increase surface roughness of FR impregnated and un-treated (control) Scots pine specimen. DAP was the most effective chemical in terms of reducing gloss loss and surface roughness of Scots pine after 750 h UV irradiance exposure. UV irradiance caused a dark, reddish, and yellowish color of impregnated and un-treated (control) Scots pine specimen after all UV irradiance periods. Total color changes in color (∆E*) exhibited a systematic trend to higher values with increasing UV irradiance time. Total color changes of ZC impregnated Scots pine were the lowest after 750 h UV irradiance exposure.
Ultimate compression strength parallel to grain (UCS) of wood is one of important performance to evaluate the structural security of old wood buildings. Poplar wood (Populus tomentosa Carrière), Chinese larch wood (Larix gmelinii (Rupr.) Kuzen.) and Chinese fir wood (Cunninghamia lanceolata (Lamb.) Hook) were selected as the models in this paper. The aim of study is to predict UCS of wood by using resistograph and screw withdrawal methods. Compared with the screw withdrawal method (SW), resistograph method (RM) is generally more reliable, but because of the expenses involved, SW should also be considered as a much cheaper alternative. The results showed that the correlation coefficient between the RM and the UCS ranged from 0.5 to 0.7. The correlation coefficient between the double-start thread screw withdrawal force (SWDST) and the UCS distributed from 0.1 to 0.65, while the values of coefficients for the singlestart thread screw withdrawal (SWSST) differed from 0.4 to 0.65. In screw withdrawal method, greater pitch of screw resulted in higher correlation coefficient.
The influence of porosity, relative bonded area and air permeability on water absorption of unbeaten and beaten bleached kraft pulps from different wood species used for tissue paper production was investigated. The water absorption was determined by four different methods such as absorption of water after immersion, initial water absorption, water absorption capacity and saturation rate with water. Linear dependences between water absorption parameters and the structural parameters of individual pulps as well as all tested pulps were obtained. The correlation coefficients obtained within individual bleached kraft pulps were from 0.95 to 1.00 and within the whole group of pulps were from 0.86 to 0.98. Relative bonded area and air permeability were found to be the most suitable parameters for predicting of initial water absorption and saturation rate with water.
This article investigated properties of different lignocellulosic biomasses. Both acidified and non-acidified sodium chlorite were used to treat wood chips and sugar cane bagasse. Images were part of characterizations that included X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). Interestingly the results indicated that biomasses followed the similar crystallinity trend while thermal stability and functional groups on the cellulose surface seemed to differ. All the FT-IR spectra showed 8 main peaks but spectra of bagasse have an additional peak. Stretching vibrations of the O-Hand the C-H stretching group in cellulose molecules were clear for all biomasses. The treatment clearly removed most of aromatic compounds normally attributed to lignin and hemicellulose.
In this paper we compare the anatomical features (number of fibrous elements in the pulp unit, fiber length, diameter of fibers and lumens, coefficients of slenderness, flexibility and the Runkel coefficient) of both Miscanthus giganteus and birch wood. The raw materials were tested prior to pulping, after pulping and after refining. Comparisons of defibering ability and selected strength properties (CMT, SCT, tear resistance, burst) allowed evaluating the papermaking potential of neutral sulfite pulps obtained from the above-mentioned raw materials.
This study aimed to determine the effects of alkaline solvent treatment on the physical properties of cork, and to analysis the filtrate components of cork after cooking treatment. Potassium hydroxide (KOH), alkaline hydrogen peroxide (AHP), and ammonium hydroxide (AOH) were used as solvents. The properties of treated cork including color, volume, hardness, compression resilience ratio, and filtrate components of different solvent treatments were investigated. The results showed an increase in the cork’s volume, changes in color, and decrease in lightness after three solvent treatments. Hardness and compression resilience decreased after three solvents cooking, and the difference in the compression resilience ratio between 15 min and 24 h was at a minimum when cork was cooked in KOH solvent. The analyses of filtrate components after KOH and AHP cooking treatments indicated that the hemicelluloses content was generally higher than lignin content. Moreover, water-soluble lignin, obtained from the three solvent filtrates, consisted of a small amount of monosaccharides, such as arabinan, galactan, glucan, and xylan. Nuclear magnetism (NMR) spectra analysis demonstrated that the lignin in KOH and AOH filtrates consisted of G units and H units, while S units only appeared in KOHimmersed lignin. This study shows that solvent treatment changes cork’s physical and chemical properties based on the solvent type and concentration.
Bark is much underutilized material. Most of the bark is used as fuel and for landscaping but there are still significant amounts of unused bark, hence creating a problem when disposed. Due to the aspects like colour, shape/size and ratio, and mechanical properties, bark is not a desired constituent for particleboard production. One of the possible uses of bark is related to its chemical compositions, specifically due to the phenolic-like components, bark can be used as formaldehyde scavenger.The aim of the paper is to present the usability of bark as particleboard formaldehyde scavenger. Single-layer particleboard made from wood particles spruce (Picea abies) and pine (Pinus sp.) bark mixture using urea-formaldehyde and melamine-urea formaldehyde as resin were tested for formaldehyde release. The formaldehyde release was determined by the Perforator method (EN 12460-5), gas analysis (EN 12460-3) and Flask method (EN 717-3). The experiment showed that the presence of bark lowers the formaldehyde release.
Wooden activated carbon hollow fiber (WACHF) is successfully synthesized from liquefied rubber wood (Hevea brasiliensis) using H2O activation. The structures of WACHF are studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and N2 adsorption. The effects of activation temperature on methylene blue (MB) and iodine adsorption property were also studied. Results show that both wood hollow fiber (WHF) and WACHF have a smooth surface and hollow fibrous structure with an average hollowness of about 76.43%. With increased activation temperature, the graphite-like microcrystalline structure has been formed. In addition, WACHF has high Brunauer-Emmett-Teller (BET) surface area (1949 m2.g-1) and total pore volume (1.246 cm3.g-1), where the contribution for micropores is 47.4% and 46.3% for the mesopores. At 800°C, the MB adsorption and iodine adsorption of WACHF reach the maximal values of 412.6 mg. g-1 and 1123.7 mg. g-1, respectively. As a result, WACHF with double surface structures has great BET surface area and excellent adsorption property.
This article describes in detail the construction and operation of the test rig employed for experimental pulse-jet filtration of air polluted with small wood particles created during machining. It enables evaluation of filter media used for wood dust separation and examination of influence of filtration conditions on the filter performance. Exemplary results of some experiments were presented to illustrate research possibilities of the testing filter and the method. More detailed results of studies on the filtration mechanisms and key parameters which determine the performance of a filter will be presented in further papers.
This study was conducted to determine the lignin and sugars contents of yellow poplar (YP) sawdust immersed in tap water (TW), sulfuric acid (AC) and sodium hydroxide (AK) solutions. Klason lignin content of TW- and AC-immersed YP sawdust was higher than that of AK-immersed YP sawdust. Glucose showed the highest content among sugars extracted from YP sawdust. Durability of non-immersed YP pellets was the highest, followed by TW-, AC- and AK-immersed YP pellets. YP pellets became more durable by increasing the Klason lignin and xylose contents as well as decreasing the glucose content. Through microscopic observations and quantitative analysis of lignin distribution, lignin content on the surface of non-immersed YP pellets was higher than that of TW-, AC- and AK-immersed YP pellets. In conclusion, there are significant correlations between lignin or sugars contents of YP sawdust and fuel characteristics of wood pellets fabricated with the YP sawdust.
An analysis of accidents has shown that many fatal and serious accidents during woodworking result from kickback. This study assessed the influence of cutting conditions on hazards associated with kickback in milling wood materials. The research concerned the severity of hazards but not the probability of kickback. The speed of kickback was accepted as the quantitative measure of these hazards. An original method of kickback experimental testing on unique research test stand was applied. The speed of kickback was measured in different cutting conditions. The experiment involved controlled changes in cutting conditions, such as the type of cutting tool, cutting speed, machined material, and tool wear. Statistical analysis of the results verified some common opinions and ideas on the impact of basic cutting conditions on the hazards resulting from kickback during milling of wood materials. In some cases, the results of empirical testing did not confirm the commonplace opinions.
Rubberwood (Hevea brasiliensis) was thermal modified by hot pressing in an open system at three different temperatures (170, 185, 200°C) and two different durations (1.5, 3 h), and the effect on the physical and mechanical properties was studied. Results show that the thermal modification increased the oven-dried density and decreased the EMC (equilibrium moisture content) by 7.93% and 37.15%, respectively, and the dimensions stability was improved. Hardness, bending strength, modulus of bending and compressive strength parallel to grain of modified samples basically decreased with increasing temperature and time, but they showed a meaningful increase compared to control samples. However, impacting bending and nail withdrawal resistance decreased after hot pressing and thermal treatment, and the failure of the compensation for the impairment was the rubberwood hot pressed and thermal treated in the presence of air, and the participation of oxygen provoked rapid degradation reactions during the treatment.