Volume 11 Issue 2

The main objective of this study was to determine the mold resistance and mechanical properties of fungicide-treated wood and bamboo flour/high density polyethylene (HDPE) composites. Zinc borate (ZB), 4,5-dichloro-2-octyl-isothiazolone (DCOIT), zinc pyrithione (ZPT), and carbendazim (MBC) were used as fungicides. Then, treated and untreated samples were exposed to mold fungi (Aspergillus niger, Trichoderma viride, Penicillium funiculosum, and Aureobasidium pullulans) for 28 days. Mechanical properties, including the tensile strength, modulus of elasticity (MOE), modulus of rupture (MOR), and impact strength of treated and untreated composites, were evaluated. The experimental results indicated that incorporation of all four fungicides greatly improved the mold resistance of wood flour/HDPE composites. ZB-, DCOIT-, and ZPT-treated bamboo flour/HDPE composites were also more resistant to mold fungi, while no inhibitory effect on mold growth was observed for MBC-treated bamboo flour/HDPE composites. In most cases, fungicides lowered the tensile strengths and MOR of wood flour/HDPE samples but increased the impact strengths of wood flour/HDPE composites and tensile strengths and MOE of bamboo flour/HDPE composites, while other mechanical properties behaved differently. Accordingly, some fungicides can be effectively used as preservatives for both wood flour/HDPE and bamboo flour/HDPE composites.

Aspen wood was subjected to autohydrolysis as a pre-treatment to characterize the structural changes occurring in lignin fractions during the pre-treatment process. Milled wood lignin (MWL) was isolated from both the native aspen wood and hydrolyzed wood chips, and its structural features were characterized by Fourier transform infrared (FT-IR), quantitative 13C, two-dimensional heteronuclear single quantum coherence (2D HSQC), and 31P nuclear magnetic resonance (NMR) spectroscopies, gel permeation chromatography/multi-angle laser light scattering (GPC-MALLS), and thermal analysis. The lignin remaining in the hydrolyzed wood chips revealed more phenolic OH groups, fewer aliphatic OH groups, higher syringyl/guaiacyl ratios (S/G), higher molecular weights, and narrower polydispersities than the native lignin of aspen wood. The inter-unit linkages of β-O-4 were noticeable cleaved, but the condensed structures in the lignin formed when undergoing autohydrolysis of high severity, resulting in elevated amounts of C-C linkages. Moreover, it was found that autohydrolysis promoted the removal of -OCH3 groups and increased the thermal stability of lignin fractions.

Effects of the type of biomass and temperature, with longer residence time, on physicochemical characteristics of hydrochar were investigated. Different carbonization conditions were applied with the goal of producing hydrochars having better physicochemical properties. After the carbonization process, the pyrolysis and combustion behaviors of hydrochar were evaluated. The effect of temperature on the chemical characteristics of hydrochar was obvious. The yield and heating value of hydrochar were high for raw materials. Even though the yield of hydrochar from water hyacinth was low, the morphology of this hydrochar was the best among all biomass samples tested. Hydrochar derived from water hyacinth can be used as a new kind of carbon material, which can improve the utilization of biomass resources. The pyrolysis and combustion behaviors of hydrochar were studied; the corresponding kinetic parameters were determined by thermogravimetric (TG) analysis. With increasing heating rate, the TG and differential thermogravimetric (DTG) curves moved to high temperatures. The combustion of hydrochar had two stages: volatilization and fixed carbon combustion. The activation energy of the wheat straw was 37 kJ/mol, and the activation energy of the water hyacinth was 51 kJ/mol. This data indicated that the combustion of water hyacinth hydrochar was difficult.

Xylanase treatment can be an environmentally friendly way to improve the formability and drainability of chemi-mechanical pulp (CMP). Improvements in xylanase treatment efficiency are possible with application of an ultrasonic wave via the cavitation effect. Results showed that the specific surface area (SSA) of the combined treated pulp increased by 14.6% at an ultrasonic treatment of 30 min and xylanase dosage of 10 U/g, in comparison to xylanase treatment alone. Also, the drainability of xylanase-treated pulp increased from 450 to 500 mL, and it further increased to 775 mL with ultrasonic-assisted xylanase treatment. Morphological characterization of pulps showed an enhanced fibrillation for the combined treatment, as shown by scanning electron microscope (SEM) images. In addition, the dimensions of treated fibers were negligibly affected.

In this study, sugar palm-derived cellulose (SPC) composites were prepared and utilized as reinforcement material to improve the mechanical and water vapor barrier properties of sugar palm starch (SPS)-based films. Cellulose-reinforced SPS composite films (SPS-C) were prepared with different SPC loadings (1 to 10 wt.%) using a solution casting method. The mechanical properties of the composite films showed increased tensile strength and modulus, while the elongation at break decreased with SPC loading. Adding 1 wt. % SPC loading significantly improved the water vapor permeability (WVP) of the composite film by 63.53% compared with the neat SPS film. This was ascribed to the high compatibility between the SPC and SPS matrices, which was supported by the field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) results.

Porous cellulose beads were prepared through a simple, facile, and inexpensive method. The resultant microspheres exhibited good spherical shape with a diameter of 1 to 2 mm. Their morphology, pore structure, and physical properties were characterized by scanning electron microscopy, X-ray diffraction, and nitrogen adsorption. The regenerated cellulose was shown by scanning electron microscopy images to have a three-dimensional porous structure, which led to a BET surface area as large as 108 m2/g. These qualities make the beads potentially useful as adsorbents or carriers. The beads remained in the cellulose I structure. Finally, the cellulose beads were tested for the adsorption of pectinase; adsorption was a favorable spontaneous process. Moreover, adsorption was in agreement with the Langmuir isotherm with a capacity of 7.40 mg/g, signifying that pectinase adsorption was a monolayer sorption. Adsorption followed an intraparticle diffusion kinetic model, indicating that intraparticle diffusion was the rate-controlling mechanism. This information will aid in the potential utilization of regenerated cellulose microspheres as supports for pectinase.

Rigid polyurethane (PUR) foam is one of the most important insulating materials used today in the construction industry and is the main insulation material used in the global appliances industry. This study developed rice straw fiber-filled PUF (RPUF) and wheat straw fiber-filled PUF (WPUF) and explored the morphology, sound absorption properties, heat transfer, and compressive strength of the PUF composites. The results indicated that, with the higher fiber content, more open cells were observed in SEM images of the composites. The average sound absorption coefficients (ASAC) of both WPUF and RPUF were significantly increased when 5 per hundred polyols (php) by weight and 10 php fiber contents were added. When fiber contents of 15 php and 20 php were utilized, ASAC reduced due to the tortuosity of cells and large holes in the foam. The sound absorption coefficient (SAC) first increased, then decreased, and increased finally as the sound frequency increased from 100 to 2000 Hz for the two composites. The thermal conductivities of both WPUF and RPUF first decreased and then increased as the fiber content increased from 0 to 20 php. When 5 and 10 php straw contents was added, the thermal conductivities were reduced by 25% to 50% compared to that of the pure PU form (0 php), indicating that the improved thermal insulation ability was obtained. The composite compressive strength was reduced by 19% to 28% due to the fiber addition.

Wood-plastic composites (WPCs) – one of a number of promising classes of materials in the manufacturing industries – are experiencing rapid market growth. However, the favorable characteristics of this material and the development of new production processes and post-production processes suggest even greater potential for utilization of WPCs. This paper evaluates the formability of an extruded WPC material comprising nearly 45% wood fiber, 50% thermoplastic, and 5% of other additives in a novel extrusion-based post-production process. The press-forming process described in this work is used to form and cut the pre-determined profile shape to obtain the final product. After preliminary tests to determine the suitable temperature range, dimensions, and roughness range for a post-extrusion hot-pressing process of a sample WPC product, a diverse set of product quality tests were then conducted on pre-heated sheets of WPC material using forming tools attached to a hydraulic press. The forming process had high accuracy with respect to dimensional precision and acceptable repeatability. The forming process also reduced the surface roughness of the material. The test results clearly demonstrated the dependence of final product quality on the quality of the original extruded WPC profiles used, e.g., with respect to the thickness variation of the material.

Crude extract samples of Pleurotus pulmonarius and Pycnoporus cinnabarinus were taken during growth in liquid broth in an airlift reactor. Growth was monitored indirectly by sugar consumption and pH profile. During growth Pleurotus pulmonarius consumed glucose more slowly than Pycnoporus cinnabarinus, reaching a final pH of 8.0. In contrast, Pycnoporus cinnabarinus started consuming glucose faster from the beginning to the end with a pH of 3.6, suggesting the production of different metabolites while they grow in the same culture broth. Additionally, antioxidant activity, polyphenol and flavonoid contents, as well as laccase and hydrolase activities were quantified in the culture extracts during the fermentation. Pleurotus pulmonarius showed higher antioxidant activity than Pycnoporus cinnabarinus. Both fungi have a very low polyphenol and flavonoid content. Values of amylase and pectinase activities were similar in crude extracts of both fungi; however, cellulase, xylanase, invertase, and laccase activities showed higher levels in crude extract of Pleurotus pulmonarius. Antimicrobial and insecticidal activities were also evaluated in each crude extract. In fact, Pycnoporus cinnabarinus presented a very strong bacteriostatic and bactericidal effect against Escherichia coli and Staphylococcus aureus and reliably killed Diatraea magnifactella larvae, while Pleurotus pulmonarius did not showed any negative effect on the growth of these bacteria or larvae.

In industrial wood grinding, logs are pressed against a rotating stone, with the logs and fiber axis parallel to the axis of the stone. The objective of this study is to clarify how the wood alignment affects the process and pulp properties. In this research, wood blocks were fed into a laboratory grinder with various alignments in relation to the surface of the grinding stone. The effects of the alignment on the properties of the pulp and the amount and quality of fines were measured. A grinding mechanism was proposed. The results show that the pulp quality is very sensitive to the angle between the stone surface and the log. In gentle refining, the fiber structure is loosened by fatigue before it is bent on the surface; pressure pulses produce fibrillar material, and fibers develop toward having good bonding ability. In forced grinding, the process is “violent”, and the fiber wears and becomes crushed immediately on the surface into small particles with low bonding ability.