Research Articles

Golf tees with a plastic head and wooden shaft were prepared by back injection moulding of a beech wood (Fagus sylvatica) shaft with different polymers (i.e. ionomer, polypropylene, and polyamide). In order to facilitate adhesion between the polymer melt and the wood surface, the wooden shafts were pre-treated with different primer substances, including a commercially available primer for ABS edges, a 10% solution of alkyl ketene dimer (AKD) in toluene and tumbling lacquer. The mechanical strength of the wood-plastic interphase was characterized by applying a pull-out test. Bond strength values of more than 9 N/mm² were observed for polyamide, whereas ionomer and polypropylene specimens achieved values between 0.7 and 3.8 N/mm². Surprisingly, the used primers failed to improve interfacial adhesion with the exception of the ionomer sample pre-treated with the commercial ABS-primer. Although light microscopy and SEM revealed some differences in the penetration behaviour of the different polymers as well as in the extent of plastic wood deformation imposed during injection moulding, the chemical nature of the polymer seems to be the most important determinant for the bond strength of wood-plastic hybrid components.

In order to improve the physical properties and brightness of poplar chemi-mechanical pulp, a new staged alkali and hydrogen peroxide treatment method was proposed and applied. Wood chips were impregnated and swelled with an alkali solution and then treated with a hydrogen peroxide bleaching liquor. A thorough evaluation and comparison of the physical properties and brightness of the pulps that underwent different treatment methods was conducted. The results showed that when the pulp was treated with an alkali and hydrogen peroxide treatment method with an alkali dosage of 6% and a hydrogen peroxide dosage of 6%, the tear index was 3.64 mN‧m2/g, the tensile strength was 3.61 kN/m, and the pulp brightness was 67.1% (ISO). The obtained physical properties and brightness of the alkali and hydrogen peroxide method treated pulp were greater than the traditional alkaline hydrogen peroxide method values, as well as the values of any other single treatment methods.

The volatile organic compounds (VOCs) emitted from wood-based panels are hazardous to indoor air quality. Usually, the VOCs are derived from the adhesive, chemical compounds, and wood components. However, there has been little research focusing on the effects of manufacture conditions on the VOC emissions. In this study, the effects of density, thickness, and resin content on total VOC (TVOC) and individual VOCs were investigated by the small chamber method and gas chromatography and mass spectrometry (GC/MS). The TVOC emission from the particleboard of each manufacturing condition decreased with extended exposure time. The higher density, thickness, and resin content of particleboard at each measured time caused higher concentrations of TVOC emissions. Most of the detected VOCs were aromatics. The esters, aldehydes, and ketones showed a high increasing level with increasing particleboard density, thickness, and resin content. This result indicated that these chemical compounds were most sensitive to changes in manufacturing conditions.

A series of novel benzofuran-1,3,4-oxadiazole hybrids were synthesized and evaluated as antifungal agents. The synthetic pathway was started from salicylaldehyde, which afforded 5-(substituted benzylthio)-1,3,4-oxadiazole derivatives in moderate to good yields. The compounds were investigated for their antifungal potential against white-rot, Trametes versicolor and brown-rot, Poria placenta and Coniophora puteana fungi at different concentrations (500, 1000 ppm). The obtaining results demonstrated that most of the compounds at 500 ppm concentration did not exhibit acceptable antifungal effects but they had better antifungal activity at 1000 ppm concentration. Compounds 5a, 5c, and 5i showed inhibition percentages of 14.6%, 23.0%, and 14.7%, against the growth of P. placenta and C. puteana, respectively. Among the compounds, the 2-(benzofuran-2-yl)-5-((2,6-difluorobenzyl)thio)-1,3,4-oxadiazole (5h) hybrid was the most active one.

The wood properties of Paulownia clones determine their ultimate price and uses. This study selected superior clones with good color and mechanical properties using selection indexes. Variation in 23 5-year-old Paulownia clones was analyzed using genetic parameters, correlation analysis, and a comprehensive assessment of two color characteristics [color difference (ΔE) and whiteness (WH)] and six mechanical properties [density (ρ), hardness of the tangential, radial, and end surfaces (Ht, Hr, and He), and cleavage strength of the tangential and radial surfaces (qt, qr)]. There were significant differences (p < 0.01) in each of the eight traits among the 23 clones. There were significant negative phenotypic and genetic correlations between ΔE and WH. The six mechanical properties were significantly positively correlated genetically, showing significant positive phenotypic correlations with each other, except for ρ, Ht, and qt. With a selection rate of 8.70%, clones MB04 and L01 were selected as superior using the comprehensive selection index. Compared with the control (9501), the genetic gains of clones MB04 and L01 in ΔE, WH, ρ, qr, qt, He, Hr, and Ht were 0.40, 0.21, 10.32, 12.57, 14.81, 26.05, 28.04, and 6.84%, respectively, and the actual gains were 0.59, 0.31, 17.21, 28.45, 28.09, 34.90, 40.08, and 11.12%.

Copper ion adsorption was studied using an activated carbon from winemaking wastes. The pH, temperature, activated carbon amount, and initial copper concentration were varied based on a full factorial 2k experimental design. Kinetic and thermodynamic studies were also performed. The adsorption kinetics followed a pseudo-second-order model. The adsorption data fit best to the Langmuir isotherm, compared with the Freundlich and Temkin models. The analysis of variance demonstrated that the pH and the activated carbon dosage had the greatest influences on the copper adsorption. The obtained activation energy suggested that the copper adsorption was physisorption. The best fit to a linear correlation was the moving boundary equation, which controls the kinetics of the adsorption of copper ions onto the activated carbon. X-ray photoelectron spectroscopy revealed the existence of different copper species (Cu2+, and Cu+ and/or Cu0) on the surface of the carbonaceous adsorbent after the adsorption, which could suggest a simultaneous reduction process.

In order to improve the detection precision of internal defect in the ancient wooden structures, defect simulation tests on pine and elm commonly used in ancient buildings were performed by using stress wave detection and drilling resistance detection. Based on detection data, three typical evaluation criteria, which are the information entropy, the correlation coefficient, and residual sum of squares, were selected as a priori information. Combining with the expert’s fuzzy evaluation value, Bayesian formula was used to modify the prior information to determine the weight coefficients of the two detection methods, and a combined prediction model was established. The results show that the combination of subjectivity and objectivity enables the revised weights to more reasonably and accurately reflect the relative importance of each detection method in prediction evaluation, which reduces the forecasting error. Specifically speaking, the mean error of the combined model was reduced by 49.8% and 59.8%, respectively, compared with stress wave detection and drilling resistance detection. Moreover, the five error indicators of this combined forecasting model are the smallest in all methods, indicating the proposed method has a better forecasting effect. It provides an effective application tool for the practice of forecasting the internal defects of wooden components in ancient buildings.

Cellulose nanocrystals (CNC) were successfully isolated from oil palm empty fruit bunch (EFB) using sulphuric acid hydrolysis preceded by alkaline deep eutectic solvent (DES) pretreatment and bleaching. In this study, an alkaline DES consisting of potassium carbonate and glycerol (molar ratio of 1:7) was used as the pretreatment solvent to promote the dissolution of lignin and hemicellulose. The processing parameters of acid hydrolysis were optimized using Box-Behnken Design. The results showed that the yield of CNC was 37.1%, under the optimal conditions of 60.0 wt% acid concentration at 46.1 °C for 58.5 min. The field emission scanning electron microscopy (FESEM), chemical composition analysis, and Fourier transform infrared (FTIR) results indicated that unwanted impurities, such as hemicellulose and lignin, were efficiently eliminated from the raw EFB fibers by DES pretreatment and bleaching. The average diameter of CNC was less than 10 nm. The raw EFB fiber, treated cellulose, and CNC showed crystallinities of 38.7%, 51.2%, and 65.3%, respectively. The CNC had lower thermal stability, which was ascribed to the sulphate group present on the CNC surface.

Based on the experimental idea of reverse simulation, a quantitative area of hole was excavated at the sectional center of a wood specimen. The excavation area was 1/32S, 1/16S, 1/8S, 1/4S, and 1/2S (where S represents cross-sectional area of the complete specimen) and stress wave nondestructive testing of six sensors was performed. The stress wave propagation paths were statistically summarized to obtain the stress wave propagation velocity (Va) for two adjacent sensors, the stress wave propagation velocity (Vb) for two separated sensors, and the stress wave propagation velocity (Vc) for two opposite sensors. Furthermore, by analyzing the advantages and disadvantages of grey relation and stepwise discriminant model when both of them were used alone, a coupling model generated from them was established to dispose the test data. The attenuation ratios Ψa, Ψb, and Ψc of stress wave under three propagation paths and their relation ratios Va/Vb, Vb/Vc, and Va/Vc, a total of six groups of measured data, were selected as discriminant factors for the hole area grade of the wood specimen. The verification results showed that the discriminant accuracy of the coupling model was 100%, and it was concluded that the attenuation ratio (Ψb) of the stress wave propagation velocity for two separated sensors had the strongest discriminant ability against cross-sectional area of the specimen.

The kinetics of pyrolysis of apricot stone and its main components, i.e., lignin, cellulose, and hemicellulose, were investigated via distributed activation energy mode. Experiments were done in a thermogravimetric analyzer at heating rates of 10, 20, 30, and 40 K·min-1 under nitrogen. The activation energy distribution peaks for the apricot stone, lignin, cellulose, and hemicellulose were centered at 246, 318, 364, and 170 kJ·mol-1, respectively. The activation energy distribution for the apricot stone slightly changed; lignin exhibited the widest distribution; and cellulose exhibited the highest activation energy at a conversion degree (α) of less than 0.75. At low pyrolysis temperatures (400 K to 600 K), the pyrolysis of hemicellulose was the main pyrolysis reaction. The apparent activation energy for the apricot stone mainly depended on the pyrolysis of hemicellulose and a small amount of lignin, and the activation energy was low in the early stage of pyrolysis. With the continuous increase in the pyrolysis temperatures (600 K to 660 K), the thermal weight loss of cellulose and lignin was intense. The apparent activation energy for the apricot stone mainly resulted from the pyrolysis of cellulose and lignin, and a higher activation energy was observed in the later stage of pyrolysis.