Volume 14 Issue 1

Poplar veneers were treated with dielectric barrier discharge (DBD) plasma at atmospheric pressure, and the effects on the veneer surface feature were explored. The bonding strength of poplar plywood glued with different urea-formaldehyde resins of varying molar ratios was also investigated. The wettability and resin penetration of the veneer treated with DBD plasma were dramatically improved, especially for the UF resin with a higher formaldehyde to urea (F/U) molar ratio. The apparent contact angle of the veneer-treated plywood decreased and the resin penetration content increased as well. The bonding strength of the plywood increased in different degrees, and the wet bonding strength in particular sharply increased; when the F/U molar ratio was 1.3, the strength was improved by 138.2%. However, when the F/U molar ratio increased, the wet bonding strength improvement declined. The veneer surface image before and after the DBD treatment was invested via scanning electron microscopy, the surface was rougher and looser, which was beneficial for resin penetration. These all indicated that the balance between the characteristics of the resin and the penetration of the veneer surface is critical for an improvement in the bonding strength of plywood.

This study examined the effect of high temperature and Litsea cubeba oil with its main components against molds (Aspergillus niger, Aspergillus flavus, Penicillium sp., Penicillium cyclopium, Rhizopus sp., Fusarium sp., and Cladosporium sp.) on bamboo food packaging. Response surface methodology (RSM) with X1 (concentration of L. cubeba oil at 100, 300, and 500 mg g-1), X2 (temperature at 60, 80, and 100 °C), and X3 (time at 12, 14, and 16 h) was used to find the inhibitory periods of natural mold on packaging plates. The physical properties and the change of chemical components on the bamboo packaging plate before and after temperature treatment were determined to find the mode of action using gas chromatography–mass spectrometry (GC-MS). High temperature (at 100 °C) was a good inhibitor of all mold growth with the MIC (minimum inhibitory concentration) of 300 mg g-1; without heat treatment, no MIC was found. In addition, it was found that by using 300 mg g-1 of L. cubeba oil at 100 °C with an exposure time of 12 h, spore germination on the bamboo surfaces was completely inhibited for at least 290 days. After using high temperature, citral was detected on the surface of the packaging plates. Therefore, these components could be the key factors for inhibiting molds.

Pressboard samples with different aging degrees were prepared to study the material and discharge characteristics of pressboards with a shielding electrode. The step-up method was used for the subsequent experiment. The partial discharges of the pressboards with different aging degrees were compared and combined using Fourier transform infrared spectra, as well as electric field simulations and analysis. The microstructure of the aged pressboards was observed with scanning electron microscopy. The results showed that pre-discharge occurred mainly in the oil gap between the hemispherical electrode edge and pressboard. Aging the pressboard had no obvious effect on the discharge characteristics at the initial partial discharge stage. As the partial discharge developed, aging the pressboard resulted in a higher electric field intensity acting over a greater area, which led to a more intense discharge. Microscopic observation showed that aging and discharge destroyed the fibre, reduced the fibre width, and caused holes and fractures, which promoted further development of the discharge. The spectroscopic analysis showed that aging destroyed O-H functional groups and reduced the intermolecular forces and mechanical properties of the pressboard.

The purpose of this study was to determine how resin, a side compound of wood, and resin cleaning methods affect the adhesion strength of water-based varnishes. For this purpose, scots pine (Pinus sylvestris L.), black pine (Pinus nigra subsp.), larch (Larix decidua Mill.), and spruce (Picea abies (L.) H. Karst.), woods with different amounts of resin in their anatomical structure were examined. Physical and chemical resin cleaning procedures were applied to the samples using acetone, cellulosic (lacquer) thinner, sodium hydroxide (NaOH), sodium hydroxide + hydrogen peroxide (NaOH + H2O2), and soft soap chemicals. Later, single-component and double-component water-based varnishes were applied to these sample surfaces. The samples were then subjected to a hot and cold-check test in accordance with the principles set forth in ASTM D 1211 (1997). In the examples, the changes in adhesion strength were examined according to TS EN ISO 4624. According to the results, resin cleaning chemicals and methods reduce the adhesion strength of water-based varnishes.

Sludge-based activated carbon (SAC) was prepared with sewage sludge and Chinese medicine herbal residues (CMHR’s). An orthogonal experimental design method was used to determine the optimum preparation conditions. The effects of the impregnation ratio, activation temperature, activation time, and addition ratio of CMHR’s on the iodine value and Brunauer-Emmett-Teller surface area of activated carbon were studied. X-ray diffraction, Fourier-transform infrared spectrometer, and scanning electron microscopy were used to characterize the prepared SAC. The results showed that the optimal process conditions for preparing the SAC were as follows: an impregnation ratio of 1:4, an activation time of 30 min, an activation temperature of 700 °C, and an addition ratio of CMHR’s of 40%. The adsorption balance of the methylene blue dye was examined at room temperature. Adsorption isotherms were obtained by fitting the data using the Langmuir and Freundlich models, which showed that methylene blue adsorption was most suitable for the Langmuir equation. The results demonstrated that SAC prepared from SS and CMHR’s from a Chinese medicine factory could effectively expel dyes from wastewater.

A novel combined process, consisting of thermal-alkali pretreatment, enzymatic hydrolysis, and anaerobic digestion (AD) was utilized to methanize corn straw (CS) and cattle manure (CM) efficiently. This study aimed to identify the carbon/nitrogen (C/N) ratio of the mixed hydrolysates of CS and CM that maximized methane production in an AD reactor. Additionally, pretreatment conditions for CS and CM were evaluated. The optimum condition of pH 10 was 80 °C and 3 h of thermal-alkali pretreatment to produce 42% of hydrolysis efficiency, while a further enzymatic process increased the efficiency to 72%. The C/N ratio was optimized during the co-digestion of the mixed hydrolysates, and better performances were obtained with a C/N ratio of 11 to 30 having specific methane production from 180 to 280 mL/g CODadded. The maximum methane production reached to 280 mL/g CODadded at the C/N ratio of 20. Approximately 75% of the total organic matter from the liquid fractions of mixed hydrolysates was converted to methane. Trace elements in CM hydrolysates may also promote the methane yield. This community structure change was proposed to be an internal response for different C/N ratio adaptation. An inappropriate C/N ratio may cause accumulation of free ammonia or volatile fatty acids, which would inhibit methanogens, but not affect the acidogens.

New possibilities offered by recent modelling software allow the design of organic shapes that are appealing to architects and engineers but may encompass serious issues such as an overconsumption of materials. In this context, there is a renewed interest in systems allowing the materialization of curved surfaces such as timber gridshells, which can be defined as shells with their structures concentrated in strips. However, gridshell design becomes highly challenging if complex grid configurations and new material possibilities are combinedly explored with form generations. These upheavals highlight the need for a classification system to seize the potential and the limitations of timber gridshells to address complex geometries. The classification of 60 timber gridshells enables a critical examination in the course of the ceaseless quest for complexity in architecture by evaluating current building possibilities and predict future building opportunities in terms of form, structure, and materiality.

Efficient pretreatment and enzymatic hydrolysis is critical to achieve effective utilization of lignocellulosic biomass. In this study, the cellulase composition for lignocellulosic biomass hydrolysis was strategically optimized to improve the efficiency of vinasse saccharification and thus enhance L-lactic acid production. The results showed that the supplementation of β-glycosidase (BG) increased sugar production, and the glucose concentration exceeded cellobiose concentration after 48 h of hydrolysis. These results suggested that the addition of BG aided the hydrolysis of cellobiose and reduced the inhibitory effects caused by sugar accumulation. After 72 h to 96 h of hydrolysis, the BG supplementation improved cellobiose and glucose production by 25.7% and 27.4%, respectively. The effect of BG supplementation on L-lactic acid production during the fermentation of microwave-alkali pretreated vinasse was also investigated. Here, the L-lactic acid production from simultaneous saccharification and fermentation (SSF) with the addition of BG was 20.8% higher than that without BG addition, and was also 37.0% higher than production from separate hydrolysis and fermentation with BG addition. These results indicated the utilization efficiency of lignocellulosic biomass for L-lactic acid production could be enhanced by supplementation of BG in SSF.

Research interest has shifted from synthetic fiber to natural fiber due to environmental concerns and government regulation. This study evaluated the physical and mechanical properties of kenaf(K)/bamboo(B) fiber mat reinforced epoxy hybrid composites. Kenaf, bamboo, and kenaf/bamboo hybrid composites were prepared using the hand lay-up method at 40% wt total fiber loading. Different ratios of kenaf to bamboo fibers, such as 70:30(3B7K), 50:50(BK), and 30:70(7B3K), were used to fabricate the hybrid composites. Kenaf composite and bamboo composite were fabricated as controls. Mechanical (flexural and impact), morphological, and physical properties (thickness swelling, water absorption, and density) were examined. The density, water absorption and thickness swelling of the composites increased as the kenaf weight ratio increased. The flexural properties of kenaf composites were improved by hybridization with bamboo fiber, whereas the impact properties of bamboo were improved by hybridization with a woven kenaf mat. Hybrid composites with a 50:50 ratio showed the highest flexural and impact strength. Scanning electron microscopy (SEM) of flexural fracture showed that 50:50(BK) displayed better interfacial adhesion than the other two ratios. The woven kenaf/bamboo hybrid composite is suitable for use in the fabrication of automotive components.

An environmentally friendly starch-based wood adhesive was developed using cassava starch (CS) and polyvinyl alcohol (PVOH). A set amount of polymethylene polyphenylene isocyanate (PAPI, modified in the laboratory) was used as the cross-linking agent to improve the water resistance. To evaluate the mechanical properties of the adhesive, the shear strength was measured by a mechanical testing machine. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were used to characterize the properties of the adhesive and the curing products. The results indicated that the adhesive using PVOH with a low alcoholysis degree was better than high alcoholysis degree and adding 7 wt% PVOH1 (RS-1717) could obtain good mechanical properties; the dry shear strength was 7.77 MPa, reaching 1.36 MPa in the wet state. The favorable results were attributed to reactive hydrogens in the wood and CS, which can form a cross-linking network with the -NCO groups of PAPI to obtain excellent shear strength and water resistance.