The relationship between bulk density and thermal conductivity in various korean woods

The article deals with the effects of bulk density on thermal conductivity in specimens of 15 Korean woods (Zelkova serrata, Pinus densiflora, Cornus controversa, Betula schmidtii, Betula platyphylla var. japonica, Ginkgo biloba L., Cedrela sinensis A. Juss., Fraxinus mandshurica, Ulmus davidiana var. japonica, Prunus sargentii Rehder, Paulownia tomentosa (Thunb.) Steud., Larix kaempferi (Lamb.) Carrière, Robinia pseudoacacia, Kalopanax septemlobus and Tilia amurensis). The results of this study were compared with previous studies performed on wood specimens from China, India, and Turkey. Consistent with these previous studies, bulk density and thermal conductivity were positively correlated in Korean woods, and a simple regression model with a very high correlation of R2 (94%) was obtained. Interestingly, we observed some variation between our simple regression models and those generated by previous researchers who had examined non-Korean woods.

Seasonal dynamic changes of sapwood and heartwood in larix gmelinii

This study describes the seasonal dynamic changes of heartwood transformation of Larix gmelinii by establishing the relationship between trunk radius, heartwood radius, sapwood width, trunk growth rings and heartwood growth rings in different heights during the growth season with regression analysis. The results showed that the initial age of heartwood formation was 7.25 years. Heartwood began to form when the trunk radius was greater than 2.6 cm, and then the heartwood radius grew 0.85 cm for every 1.00 cm growth of the trunk radius. It was also demonstrated that the significant change and growth rate of heartwood with month were higher than sapwood at the tree base and 1 m height, but lower than sapwood at 5 m and 9 m height. The absolute content of heartwood and sapwood area decreased with tree height, however, the relative content of sapwood area increased with the tree height.

Decay resistance of preservative injected poplar and its process of preventing white rot fungi infection

This study initially investigated decay resistance of preservative injected poplar and its infection mechanism of preventing white rot fungi. The living poplar was injected with different concentrations (0.0, 0.5, 1.0 and 1.5 wt.%) of alkaline copper quaternary (ACQ). Using the scanning electron microscopy, the process of preservative injected poplar wood preventing white rot fungi infection at different tree heights were examined. The decay resistance test results showed that the decay resistance of preservative injected poplar at different tree heights was significantly different. With the increase in tree height, the decay resistance decreased, and the higher the ACQ concentration, the better the decay resistance. The white rot fungi infested the poplar wood with the vessels as the breakthrough point, being spread to other cells through pits. The white rot fungi degraded wood cell walls by secreting enzymes and preferentially degraded the parenchyma cells.

Enhancing leucaena leucocephala wood preservation by steeping it in boron compounds and acetic acid to protect against termites

This study compared steeping Leucaena leucocephala wood with boron compounds and acetic acid to protect it from termites (Coptotermes gestroi). The experiment had a completely randomized design with 10 treatments involving three wood preservatives (acetic acid, boron compounds, and mixtures of both), three treatment lengths (1, 12, and 24 h), and untreated wood, with five replicates of each for a total of 50 conditions. The moisture content of the wood and the wood destroyed by termites were assessed. The L. leucocephala wood treated with boron compounds for 1 h resulted increase in moisture content and no termite damage.

Effects of differrent boron-based flame retardants on the combustibility of bamboo filaments

In this study, eight types of boron-based flame retardants were performed to evaluate the effects of different boron components on the combustibility of the bamboo filaments. Disodium octaborate tetrahydrate, boric acid/borax, and nano-ZnBO4 were used as the active flame retardant components. Besides, other inorganic flame retardants including nano-SiO2 and ammonium polyphosphate (APP) were also introduced in order to increase the flame retardant of these boron-based components. The combustibility of the bamboo filaments treated with different flame retardants were evaluated by cone calorimeter analysis. The results showed that the flame retardants including the heat release and smoke release resistance of the bamboo filaments with different boron-based components and nano-SiO2 or APP, could be significantly improved, especially, in the samples treated with the compound flame retardant composed of boric acid, borax and nano-SiO2, which was attributed to the synergistic effect of these flame retardant components.

Analysis of moisture content variation on strength and stiffness properties of cedrella odorata wood species

In order to analyze the influence of moisture content variation on Cedrella odorata wood specie on strength and stiffness properties, considering 12% moisture content up to fiber saturation point (FSP). Most of strength and stiffness properties analyzed were significantly influenced by moisture content according statistical analysis. ANOVA, Anderson Darling and Multiple comparison tests were used at 5% significance level. Considering that most of properties were affected by moisture content, the equations to estimate wood properties according moisture decrease are quite precise, but most of estimations were higher than experimental values at 12% moisture content, indicating the need of a standard review for such estimators, which may lead to an unsafe timber structure design.

Properties of the water-resistant plywood glued with pf resin with the addition of tannin filler and nanoclay

The conducted study was aimed at finding the phenol-formaldehyde adhesive formulation containing both the nanoclay and the tannin filler which allows to manufacture water-resistant plywood characterized by the improved properties. The research assumed the application of six experimental variants having a different proportions of the mentioned components which were compared with the mixture prepared according to the industrial recipe. Properties of liquid mixtures such as their gelation time and viscosity were investigated. Moreover, the differential scanning calorimetry (DSC) was performed. The manufactured plywood panels were tested in terms of bonding quality, bending strength and modulus of elasticity. Studies have shown that after the adjustment in components proportions it is possible to achieve the proper viscosity level of adhesive mixtures. The results also indicated that the suitable amount of nanoclay can contribute to the acceleration of resin gel time, however, the DSC analysis showed no effect on its reactivity. The nanoclay concentrations ranging from 2 to 4 pbw (parts by weight) per 100 g of adhesive positively influenced the bonding quality of plywood. Furthermore, there was no clear tendency in case of the effect of applied formulation on the modulus of elasticity and bending strength of plywood. The mixture containing 3 pbw of nanoclay and 5.3 pbw of tannin filler was distinguished as the most beneficial taking into account the improvement in the properties of manufactured plywood.

Modelling a clt specimen protected with gypsum exposed to parametric fire curve heat flux

This paper models bench-scale experiments using computational fluid dynamics (CFD). The experiments measured the temperature profiles of fire-protected cross laminated timber (CLT) specimens exposed to parametric fire curve. The bench-scale experiment specimen is 250 x 250 mm and consists of a CLT panel 100 mm with three layers of gypsum plasterboard 15.5 mm as thermal and fire insulation The specimens were exposed to a heat flux generated by a heat-transfer rate inducing system (H-TRIS) device. Two numerical models were created in order to copy the experiment conditions, one by using basic modelling techniques and one using advanced method. Comparing the layer temperature values of the experiment and basic model, a great difference was found. The difference between experimental and model temperatures increases the closer the analysed layer is to the heat source. The results show a good agreement between the model and the experiments, especially for the advanced numerical model.

Study on flame retardant leach resistant of modified poplar wood

After flame retardant and enhancing treatment, fast-grown poplar face the problem of leaching of pharmacy, which affected the effective permanence of the retard and further use is limited. In this paper, we study the fixed effect of low molecule phenol-formaldehyde (PF) resin on nitrogen and phosphorus (N-P) inorganic flame retardant composite under the condition of high relative humidity. The change of lateral sizes and quality of the specimens were emphasized in the experiment. Results reveal that the greater the concentration of flame retardant was, the greater weight gain percentage of the samples was, and the more serious leach was in the test, after the specimen was modified with the flame retardant. When weight gain percentage of the specimens is same, the greater the concentration of PF resin test solution was, better effect of the leach resistant will be obtained with the concentration of PF test solution increased. The PF resin with 25% concentration had the best effect to reduce the leach of N-P inorganic composite retards. From the comparative analysis above, it was advisable to indicate the PF resin with 25% concentration had the best effect to reduce the leach of N-P inorganic composite retards.

Determination of mode I fracture behavior of southern yellow pine (Pinus taeda L.) wood using single-edge-notched bending test

The fracture behavior of southern yellow pine (Pinus taeda L.) was experimentally analyzed in the radial-longitudinal and the radial-tangential crack propagation systems using a single-edge-notched bending test method in mode I loading condition. Three fracture parameters, the initial slope, the fracture toughness, and the specific fracture energy, were determined from the obtained load-deformation curves of each test sample. The results were statistically analyzed and compared with each other using the independent samples t-test. The radial-longitudinal crack propagation system had a significantly greater fracture toughness than in the radial-tangential crack propagation system. The stiffness in the radial-longitudinal system was also significantly higher than in the radial-tangential system. It was observed that the crack growing in the tangential direction needed more energy per unit area to separate a wood sample into two halves. However, there was no significant difference between the specific fracture energy values of crack propagation systems.

Design and performance of nail connection in wood framing shear walls

As the preferable lateral resistance system of a wood shear wall is attributed to the good lateral performance of nail connection, this paper aims at investigating the pull-out and shear performances of framing members’ nail connection in wood shear walls under monotonic loading. It was found that the main failure mode of the pull-out behavior of nail connection was the withdrawal of threaded nails from framing members. In addition, the shear behavior of nail connection was characterized by plastic hinge of threaded nails, local tear of spruce-pine-fir (SPF) on the top of nails, and nail caps that were obliquely embedded into the surface of SPF. The average ultimate load and displacement of shear mode were 1.48 times and 5.12 times higher than those of pull-out mode, respectively. According to the research results, the corresponding exponential numerical model was established, which provided basic data for the lateral performance research and finite element simulation analysis of wood shear walls nail connection.

Effect of wood flour content on the properties of flat pressed wood plastic composites

This study focused on the effect of wood flour content on some mechanical and physical properties of flat pressed wood plastic composites (WPC). The results revealed changes in the wood flour content affected the density of flat pressed WPC. Moreover, as exposure time increased, water absorption values were increased. The changes in the wood flour content considerably affected the mechanical properties of WPC. The decrease in the flexural strength reached up to 58%, while it was 61% for tensile strength. However, modulus of elasticity increased with increasing wood flour content. Meanwhile, the decrease was inevitable for screw withdrawal strength, where the increase in wood flour content resulted in a reduction of up to 50%. It was clearly determined that wood flour content above 60% evidently affects the physical and mechanical properties of flat pressed WPC, which should be considered in the utilization areas where high mechanical properties are critical.

The tactile perception evaluation of wood surface with different roughness and shapes: A study using galvanic skin response

By adopting the methods of PAD subjective emotion measurement and galvanic skin response physiological measurement, this study explores the differences in people’s tactile perception evaluation of the surfaces of beech materials with different roughness and shapes. The results show that females prefer beech samples with arc shapes, while males prefer the samples with rectangle shapes; participants’ emotional stability under a higher emotional arousal level can to a certain extent be maintained due to the beech materials with arc shapes. The tactile perception of males for beech materials has a greater range of emotional arousal than that of females, but the arousal speed of males’ emotions is lower than that of females’ emotions. Moreover, a better tactile perception experience can be created for participants when the roughness of beech materials is limited within a certain range of conditions, and a certain sense of “anxiousness” will be brought to participants if the surface of beech materials is too rough.

Study on thermal comfort of wood tabletop materials

The purpose of this study is to investigate the contact temperature and thermal comfort when the upper extremity touches a wooden table top, and to seek an efficient accurate simulation device instead of human testing. Therefore, three parts of this paper were conducted. First, 20 subjects were selected for the temperature test experiment. Secondly, the perceptual thermal comfort evaluation was quantified by recording the thermal comfort evaluation at a specific moment. Finally, a device was developed to replace the human forearm for upper limb thermal comfort study. The results show that the ambient temperature, type and thickness of material all have significant effects on the local contact temperature. In terms of thermal comfort evaluation, the correlation between temperature and thermal comfort was significant. The simulation device in the study is not only simple to operate, but also can continuously and stably replace the heat transfer process of the upper limb.

Methods of preparation of nanofibrillated cellulose for special filter papers with effective air filtration. Short notes

Nanofibrillated cellulose was prepared from distillery refuse based on maize starch using the extraction with NaOH and HCl involving centrifugation. SEM images of bleached kraft pulp with/without the addition of nanofibrillated cellulose were compared. The results showed that the application of nanofibrillated cellulose caused a visible reduction in the surface porosity. Conversely, mixing of the pulp with the nanofibrillated cellulose resulted in large pores among the fibres. The effect of the cationic retention aid on porosity was not significant, observed in the fines retention. A minimal difference in porosity was found among of fine and coarse fibres. When lyophilisation as drying method was used it yielded nanofibrillated cellulose with a size in the range of approximately 100 to 150 nm.