Volume 16 Issue 2

Using the methods of high-speed mixing, screw extrusion, and injection molding, wood-plastic composites (CS-PF-ASFX) with inorganic fibers (aluminum silicate fibers, ASF) and organic agricultural wastes (cotton stalk, CS) as reinforcing fillers were prepared. The effects of different contents of ASF on the properties of wood-plastic composites were analyzed. Materials were characterized by Fourier infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analyses. The creep, relaxation, and mechanical behavior were also tested. With the increase of ASF contents, the FT-IR peaks at approximately 1740 cm-1 shifted to lower wavenumber, indicating the potential interactions between ASF and CS. The XRD patterns of the composites implied that the crystal structures of each component were maintained. Moreover, the addition of ASF enhanced the mechanical properties and thermal stabilities of CS-PF-ASFX composites, and the tensile strength and impact strength reached maximum of approximately 39.4 MPa and approximately 3.89 kJ/m2, respectively.

Bamboo scrimber is a kind of artificial processing material with high compressive strength, large size, natural texture, and wide application. It is made by rolling and de-fibering bamboo into a loose reticulate bundle, which is unbroken transversely, and loosely interlaced in the longitudinal direction, followed by drying, gluing, assembling, and hot pressing. In this study, to better understand the application value of bamboo scrimber in construction engineering, the performance of axially compressed solid columns that have been completed with three full-scale solid bamboo scrimber columns of 100 mm width, 100 mm height, and 2000 mm length were subjected to creep tests for 3 months. The specimens J1, J2, and J3 were designed to carry the long-term load of 0.2, 0.4, and 0.6 times the short-term test failure load of the same batch of specimens, respectively. The experimental study found that the bamboo scrimber columns could not bear 0.6 times of the short-term test failure load Pu, and that temperature and humidity greatly influenced creep of the specimens. Finally, a creep constitutive equation was established using a three-parameter model, and the equation matched well with the creep test data.

Torrefaction pretreatment conducted at a low temperature is an important technique for refining the bio-oil and improving the production of some chemicals in the bio-oil (e.g. aromatic hydrocarbons). In this work, the effects of torrefaction temperature and catalysts on the yields of pyrolysis products and components distribution in the bio-oils were analyzed. The weak acid sites shifted to higher temperature as the HZSM-5 was modified by Mg2+ or Al3+. The catalytic pyrolysis from camphorwood was done at pyrolysis of 450 °C and torrefaction temperature of 200 °C. The catalysts remarkably influenced the yields of bio-oil and components distribution. The catalysts increased the production of phenols. The content of phenols in the resulting bio-oil exhibited the following trend: HZSM-5 < MgO-modified HZSM-5 < Al2O3-modified HZSM-5. In addition, the content of 2,6-dimethoxyphenol was the highest among all phenol components (5.58%). The production of aldehydes was remarkably improved by the Al2O3-modified HZSM-5, resulting in a maximum content of 8.21%. Thus the torrefaction temperature and catalysts would refine the bio-oil (such as the acid value decreased) and significantly improve the contents of components (such as D-allose, 2,6-dimethoxy-4-(2-propeny)-phenol, 1,2,4-trimethoxybenzene, and 2,6-dimethoxyphenol). The results provide a theoretical basis for the resource recovery of biomass.

Physical, mechanical, and formaldehyde emission properties were studied for medium density fiberboard (MDF) produced with oak (75%) and pine (25%) fibers that had been mechanically refined in the presence of calcite particles. The calcite slurry was prepared at two levels of solids, 1.5% and 3% (10 and 20 kg·m-³). Chips were cooked for 4 min at 185 °C, under 8 bar vapor pressure in an Andritz defibrillator. 1.8% liquid paraffin, 0.72% ammonium sulphate solution, and 11% urea-formaldehyde were added by percentage based on oven-dried wood fibers in the blowline at the exit of the defibrator. The fibers were dried to 11% moisture content. MDF boards (2100 mm × 2800 mm × 18 mm) were created using a continuous hot-press process. The addition of calcite in the course of MDF production resulted in improved physical properties, such as thickness swelling (ThS 24 hours) and water absorption (WA 24 hours). MDF boards prepared with calcite exhibited higher internal bond (IB), modulus of rupture (MOR), and modulus of elasticity (MOE). Resistance to axial withdrawal of screw also was increased by addition of 3% calcite. In addition, the lowest levels of formaldehyde emission were observed for MDF prepared with calcite at the 3% level.

The aim of this study was to investigate a potential biorefinery process to realize the high utilization of Camellia oleifera shell (COS), which is an agricultural by-product mainly composed of cellulose, hemicellulose, and lignin. Before treatment by steam explosion, the COS was impregnated with water, 3.0 wt% NaOH solution, or 3.0 wt% H2SO4 solution. The morphological structure and chemical composition of the steam-exploded COS pulp were investigated. The results indicated that the impregnation treatments increased the cellulose content of the steam-exploded COS pulp and decreased the hemicellulose and lignin content. The morphology of steam-exploded COS fiber was short, coarse and stiff. Hydrophobic and colorful handsheets were fabricated by mixing proportional bleached softwood fiber. This study demonstrated that COS was a potential material for the papermaking industry, and the combination of water impregnation and steam explosion treatment for COS was a good pulp process.

Starch and celluloses are biodegradable resources of great importance in terms of marketing. These biopolymers can be used to generate films with interesting mechanical, optical, and thermal properties, which can substitute for plastic films in certain applications, e.g., packaging materials. This study describes the preparation of pure plasticized starch films, prepared from soluble starch and glycerol, and the preparation of microfibrillated cellulose films from oil palm empty fruit bunches fabricated via casting. Composites made of plasticized starch were also prepared with microfibrillated cellulose added in 10% increments. The density, color difference, opacity, morphology, water activity, water affinity, and thermal and mechanical characteristics of the films were investigated. Plasticized starch is a translucent material with contact transparency; it is fragile and has relatively high water and glycerol contents. The thermogravimetric analysis of materials displayed up to four stages of weight loss related to water evaporation, glycerol, starch, and cellulose thermal degradation. As a consequence, the materials with higher cellulose content exhibited better thermal resistance. The composites with 90% of microfibrillated cellulose resulted in increased tensile strength when compared to the pure materials. The pure microfibrillated cellulose presented the highest values of Young modulus. The addition of plasticized starch to microfibrillated cellulose improved the maximum strain of the composites.

The forestry sector in Portugal faces important challenges, resulting in an increased incidence of fires and the action of pathogens, which puts the sustainability of forest resources at risk. Due to the economic, social, and environmental importance of forests, this work assessed the land use environmental impact of maritime pine and eucalypt standing in Portuguese forests. SimaPro software was used to translate the inventory table results into land use impact category. The ILCD 2011 Midpoint+ method was chosen to assess the “land use” environmental impact that focuses on soil quality and its indicator (kg carbon deficit), which describes the changes in soil organic matter associated with land interventions. The results showed that for the first rotation time, the land use impact category per cubic meter of maritime pine is 18423 kg C deficit and 23430 kg C deficit for eucalypt, which means that the land use impact category of eucalypt is 27% higher than the impact of maritime pine.

Pterocarya stenoptera bark extract (PSBE) was assessed for its chemical constituents, antioxidant activity, and antibacterial activity. The total phenolic content (TPC) in the PSBE was 272.92 ± 3.22 mg gallic acid equivalent (GAE)/g. Three phenolic compounds (quercetin-3-O-(2″-O-galloyl)-rhamnoside, quercetin, and juglone) were identified in the PSBE via ultraperformance liquid chromatography/mass spectroscopy (UPLC/MS) analysis. The PSBE possessed remarkable antioxidant activity in the DPPH and ABTS+ radicals scavenging system, with IC50 values of 96.25 ± 3.82 μg/mL and 158.26 ± 6.08 μg/mL, respectively. Moreover, the PSBE had high antibacterial activity, which was especially sensitive to Staphylococcus aureus. The antibacterial mechanism of the PSBE on the S. aureus was related to the deformation of the cell morphology and the destruction of the cell membrane structure, which was confirmed using a BacLight Viability Kit and scanning electron microscope (SEM) observations. These findings suggest that the strong antioxidant and antibacterial properties of the bark extract from P. stenoptera make the tree species suitable as a natural additive in the pharmaceutical, food, and cosmetic industries.

The possibility of using beech wood sawdust and hazelnut husk waste generated during the cultivation of Pleurotus ostreatus mushrooms as a filler in polycaprolactone (PCL)-based biocomposite films was investigated. Chemical and physical properties of the PCL biocomposites were determined. The beech sawdust and hazelnut husk were exposed to degradation for 73 d and 78 d, respectively, in slightly acidic environments at a relative humidity of 75%. The degraded materials caused the holocellulose and lignin contents in the PCL biocomposites to decrease, while the cellulose and α-cellulose contents increased. In general, as the lignocellulosic waste content increased, the tensile strength (TS) and elongation at break (EatB) values decreased and the tensile modulus (TM) and water absorption (WA) values increased. It was determined that the PCL biocomposite with the degraded beech sawdust absorbed more water than the composite with the undegraded beech sawdust. On the other hand, the PCL biocomposite with the degraded hazelnut husk absorbed less water than the composite with the raw hazelnut husk.

Lignocellulolytic white-rot fungi allow the bioconversion of agricultural wastes into value-added products that are used in a myriad of applications. The aim of this work was to use corn residues (Zea mays L.) to produce valuable products under solid-state fermentation (SSF) with Pleurotus ostreatus. White-rot fungus P. ostreatus was isolated from maize silage (MS) and thereafter it was inoculated on MS as substrate and compared with maize stover (MSt) and maize cobs (MC) to determine the best lignocellulosic substrate for the production of lignocellulolytic enzymes and extracellular protein. The MS gave the highest productivity of CMCase (368.2 U/mL), FPase (170.5 U/mL), laccase (11.4 U/mL), and MnPase (6.6 U/mL). This is compared to productivity on MSt of 222 U/mL, 50.2 U/mL, 4.55 U/mL, and 2.57 U/mL, respectively; and productivity on MC at the same incubation period as 150.5 U/mL, 48.2 U/mL, 3.58 U/mL, and 2.5 U/mL, respectively. The levels of enzyme production declined with increasing incubation period after 15 and 20 days using MS and MC, respectively, as substrates. Maximum liberated extracellular protein content (754 to 878 µg/mL) was recorded using MS, while a low amount (343 to 408 µg/mL) was liberated with using MSt and MC.