Volume 13 Issue 4

Steam treatment was used in this work to correct the observed warp in dried core-wood radiata pine (Pinus radiata) lumber that appears during the industrial drying process at high temperatures. The experimental design considered seven tests and three process variables: temperature, overload, and treatment time. The warp and moisture content before and after the treatment were measured, which allowed for assessing the efficiency of the cup recovery process of the studied thermal treatment programs. Of the analyzed types of warp (twist, bow, crook and cup), only twist was observed to be relevant to the effects of the permissible wood quality classification. The results showed that the twist recovery depends on the temperature, treatment time and overload magnitude. The best treatment results were with a steaming temperature of 100 (°C) and an overload of 3 (ton/m³) applied for 6 (h), which allowed an average recovery value of approximately 43.1%. Moreover, there was an increase in the moisture content and wood density of 10% and 3%, respectively. Finally, the post-treatment of wood with superheated steam did not show a significant improvement to the warp recovery.

Nanocrystalline cellulose was prepared from bleached softwood kraft pulp using acid hydrolysis. Acetylated nanocellulose (AcNCC) and polylactic acid (PLA) were mixed together at different proportions under certain humidity conditions using a miscible method to prepare highly regular porous AcNCC/PLA composite films. The composites were characterized using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The PLA/Ac-NCC-4 showed a uniform pore diameter distribution with diameter of 1.0 μm to 5.0 μm. The mechanical properties and thermal stability of the PLA composites were improved with the addition of AcNCC. The pore structure was regular and well distributed. When the AcNCC loading was 4%, the tensile strength and Young’s modulus of the composites were 2.07 and 2.41 times higher than that of the pure PLA, respectively. The composites also exhibited high visible light transmission.

The moisture content of wood affects its physical properties. Many researchers have attempted to measure wood moisture contents nondestructively using near-infrared (NIR) spectroscopy. Wood is a natural material with anisotropic characteristics. There are three section types of cut wood surfaces, namely cross, radial, and tangential sections. In this study the NIR spectra of all three types of wood sections were measured and compared to determine how accurately the water content of softwood could be predicted. Two wood species were chosen and were cut into 30-mm cubes. The wood samples were stored for two weeks under various humidity conditions before they underwent NIR spectroscopy. The NIR spectra were obtained from three wood sections and principal component regression (PCR) was performed. Good calibration models for the three types of sections were then obtained. Furthermore, to expand the application of the PCR model for each section type, combinations of calibration models and prediction sets of the other sections were implemented. For the cross section models, there was no clear prediction capability when the test sets from the other two section types were used. However, for the radial and tangential sections, a high prediction accuracy was obtained using the other test set.

Anionic pectic substances in whitewater are harmful to the papermaking process and product quality. To diminish their negative effect, immobilized pectinase was prepared to treat pectic compounds in whitewater. Pectinase was immobilized on pulp fiber via a layer-by-layer assembly technique using polyethyleneimine. The activity of the immobilized enzyme varied nearly linearly, from 2876 U/g to 4838 U/g, until the number of layers reached four. The properties of the bound enzymes and their free counterparts were investigated. After being fixed on the pulp fiber, the optimum pH of the enzymes shifted from 4.4 to 4.0 and the optimum temperature increased by 5 °C to 50 °C. It was shown that the V_m value was slightly reduced for the immobilized enzymes, while the K_m value noticeably decreased. Furthermore, the immobilized enzyme was tested in papermaking whitewater treatment. The four-layer immobilized enzymes lowered the whitewater cationic demand by 18% and 30% at pH values of 7 and 4, respectively. The immobilized pectinase could potentially be employed to treat wastewater in the papermaking industry.

The effect of ethylene oxide (EO) sterilization and/or accelerated ageing on impact bending strength (IBS), tensile strength along and across the fiber (TSALF and TSACF), ultimate flexural strength along and across the fiber (FSAL and FSAC), and splitting resistance (SR) was tested in bulk and veneer wood. The IBS was greatly increased in beech but decreased in some oak samples. The EO treatment followed by ageing caused the TSACF to increase in bulk beech and to decrease in bulk oak. The EO treatment decreased the TSALF values in bulk oak, beech, and elm veneer. However, beech veneer samples exhibited increased TSALF. The ageing of EO treated samples decreased the TSALF values for veneers (oak and beech), while both bulk samples increased. A notable decline was observed due to EO treatment of oak and beech, along with post ageing decline for oak samples in FSAC values only. The FSAL values decreased after ageing of EO treated and untreated samples (oak and beech), while a post EO treatment decline was observed in oak samples only. The SR (R_w) values decreased in EO-only treated oak wood and increased in EO treated and aged samples (oak and beech).

To effectively utilize sawmill slab residues, self-manufactured combing equipment was used to transform residues into individual bundle sticks. The scrimber was prepared from Chinese fir by hot pressing the resulting bundle sticks. In this study, the combing process and effects of density on the mechanical and physical properties of the scrimber were investigated. The morphology of the scrimber was tested with computed tomography. The results showed that a rotary speed of 120 rpm for the coarse roller and a rotary speed of 360 rpm for the fine roller combed along the grain were the optimum combing parameters to prepare a uniform individual bundle of sticks. The moisture content of the feeding sawmill residues was above 30%. The scrimber prepared via bundle sticks is a new type of structural scrimber, and the density of the scrimber influenced the physical and mechanical properties. As the scrimber density increased, the modulus of rupture, modulus of elasticity, and internal bond gradually increased, while the 24-h thickness swell decreased. The studied method enhanced the density and improved the physical and mechanical properties. The striped structural characteristic of the scrimber was evident, and the density distribution varied for different faults.

To extract essential oil from Melaleuca bracteata leaves without thermal degradation, ultrasound-assisted extraction (UAE) was developed and optimized using a response surface method (RSM) based on the Box-Behnken design (BBD). Under the optimized extraction conditions, a higher essential oil yield of 4.55% was achieved in comparison to that of 1.02% via the conventional hydrodistillation extraction method, which suggested that UAE could be used as an alternative and efficient extraction method for the essential oil from M. bracteata leaves. Furthermore, the composition of the essential oil extract was analyzed by gas chromatography-mass spectrometry. The results showed that 42 constituents, including methyl eugenol (86.5%), methyl cinnamate (4.33%), 3,4,5-trimethoxybenzoic acid, methyl ester (1.77%), and germacrene D (1.24%) were identified in the essential oil of M. bracteata leaves. The essential oil showed strong 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity, and reducing property. Additionally, remarkable bacteriostatic activity was observed against the tested pathogens, including Chromobacterium violaceum ATCC31532, Pseudomonas aeruginosa PAO1, Serratia marcescens MG1, and Serratia marcescens H30. These results indicated that the essential oil from M. bracteata leaves had potential applications due to its antioxidative and antimicrobial activities.

The efficiency and kinetics of methane fermentation were evaluated for six energy crops when cultivated at three different nitrogen (N) fertilization levels, specifically, maize, sorghum, sunflower, triticale, reed canary grass (RCG), and Virginia mallow (VM). In the case of the perennials, RCG and VM, the impacts of individual swath and cutting frequency were examined. A new model for predicting the methane yield based on the substrate chemical composition was developed and validated. A raised N fertilization dose increased the biogas, methane yield, and the specific rate of their production. The highest increase in methane yield was observed in VM from 145 to 197 dm³ kg^-1 of volatile solids (VS) due to a 15% rise in biodegradability. This resulted from a decrease in the lignin content and favorable changes in the lignin to structural carbohydrates ratio. Moreover, in the case of perennials, more efficient biogas production was observed for the biomass collected at an earlier stage. The results in this investigation are important for the production of high-quality biomass for biogas plants, without competition for arable land areas with food and feed production.

A novel mathematical model is reported for end-point control during displacement kraft pulping. The model was based on an on-line process that measured the dissolved lignin content in cooking liquor using an attenuated total reflection ultraviolet spectroscopy method that had been developed previously, from which a relationship between the pulp kappa number and integrated dissolved lignin content was established. The results showed that there was good agreement between the pulp kappa numbers measured by the presented model and TAPPI standard method. The presented method is straightforward and accurate and has the potential for on-line process control in mill operation.

Multilayer Plycork Aluminum (Al) composites were produced via vacuum bonding using a vacuum membrane press. The cladding material of the Plycork Al composites was an aluminum sheet, while the core material consisted of a natural cork agglomerate with varying thicknesses. Fire resistance tests and comparative static four-point bending tests were conducted on the Plycork Al composite samples. In addition, the characteristics of the deformation caused by the bending stress were compared between the Plycork Al composite and birch plywood. It was evident that this light composite can be applied as a structural material for transport purposes in railway vehicles due to its specific desirable properties. Additionally, the use of Plycork Al composites posed no toxic risk regarding the gases released during a fire and ensured vital operational safety because sharp edges did not form when the material was destroyed. In conclusion, this light multilayer composite can be frequently used to replace conventional materials employed in the transportation industry.