Volume 14 Issue 2

Three enzymatic treatments were compared for the depolymerization of cellulolytic enzyme lignin (CEL) from aspen; these systems used pyranose 2-oxidase and lignin-degrading peroxidases. The “P” system was mainly composed of pyranose 2-oxidase, lignin peroxidase (LiP), and manganese peroxidase (MnP). Catalase and vitamin C were added to the P system to decompose H2O2 to control the H2O2 concentration. The system to which catalase was added was called the “C” system. The system to which catalase and vitamin C were added together was called the “V” system. Ultraviolet-visible (UV-Vis) spectra of supernatants after aspen CEL treatment by the P, C, or V system was used to monitor the amount of water-soluble lignin fragments that were generated, which increased with system treatment time. A gel permeation chromatography (GPC) analysis showed that after 12 h of system treatment, the molecular weight (Mw) of CEL was efficiently lowered; the maximum Mw reduction of aspen CEL was 20% when compared to the blank and control runs. The residual enzymatic activity of the supernatant after the CEL treatment by the P, C, or V system indicated that MnP and LiP activity for lignin degradation was dependent upon the H2O2 concentration. Therefore, it is advised that MnP and LiP be applied separately for effective lignin degradation.

The article deals with data in the cutting process of wood-based materials. The cutting process influences the shape and dimensions of a cutting edge. The experiments were focused on monitoring the changes of the cutting edge in machining of particle board and the influence of cutting speed on the tool wear. Cutting tests were performed during milling at cutting rates in the range 7.95 to 17.9 m/s (477 to 1074 m/min), a depth of cut of 9.5 mm, and a tooth feed of 0.05 mm. The wear process of cutting wedge during particle board milling is characterized by a decrease in the cutting edge of insert blades. The comparative digital dial gauge was used for measurement of the cutting wedge recession. The course of the wear of wood based materials exhibited similarity in graphical representation with abrasive material cutting. The resulting dependency may be used for selection of the most suitable cutting conditions according to operator requirements.

In Malaysia, the depletion of raw materials has begun to impact mills, as their production could decrease or cease. This will impact the Malaysian wood-based economy, both locally and globally. Usage of trees with fast-growing characteristics is essential to add feedstock sources to mills. This study investigated the mechanical properties (MOR, MOR, IB, and screw withdrawal) of particleboard (density = 660 kg/m3) made of Leucaena leucocephala, rubberwood, and mixed tropical trees with different species ratios. The wood species ratios for the particleboards were 100% Leucaena, 50% Leucaena and 50% rubberwood, and 50% rubberwood and 50% mixed tropical wood. Boards with the dimensions 3680 mm × 2465 mm × 25 mm were produced. The results showed that all of the species ratios passed the minimum requirements for commercial use. The performance of the Leucaena particleboard was 17.40 MPa (MOR), 2654 MPa (MOE), 0.68 MPa (IB) and 623 N (Screw withdrawal). The Leucaena board performance matched that of the board made from the current raw materials used commercially (mixed tropical wood and rubberwood).

Leucaena leucocephala and Casuarina equisetifolia are two fast-growing deciduous tropical hardwoods that were characterized for their morphological and chemical characteristics to assess their suitability for pulp production. The effects of kraft pulping sulfidity, cooking time, and cooking temperature on screened pulp yield and Kappa number were studied. Handsheets made from these pulps showed a vessel picking problem during printing that was reduced by treating the pulp with 0.1% cellulase and beating the pulp at high consistency.

The water-retaining capabilities of bleached chemical pulps treated by the oven-, air-, vacuum-, and freeze-drying modes were determined with use of a reliable the headspace gas chromatographic method (HS-GC) developed recently. The results showed that reliable water retention data could be determined by the HS-GC method only in the case of air-dried pulp. This result was supplemented by observations of the surface morphology of the fibers from these drying processes. The present HS-GC method can be used for checking the differences of wettability (at a given equilibration time) of pulp specimens from different drying modes.

The objective of this work was to synthesize cellulose acetate from sorghum bagasse, a promising raw material for the production of chemical inputs, both from a photosynthetic point of view and the maturation speed compared with that of sugarcane. The bagasse was treated with hydrogen peroxide, and then cellulose was isolated using sodium chlorite, acetic acid, and sodium hydroxide. The cellulose was subjected to an acetylation reaction, from which cellulose triacetate was obtained. By means of statistical analysis, it was observed that the conditions that generated the highest solubilization of lignin (62%) and higher yield from cellulose extraction (39.5%) were 60 °C, a 6% peroxide concentration, and 4 h. Cellulose acetate was obtained with a degree of substitution of 3.66 at 25 °C and 24 h. Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, differential thermogravimetry, and differential scanning calorimetry analyses confirmed that the obtained cellulose presented specific characteristics of this material. Also, the reaction of acetylation was confirmed through these techniques.

The influence of birch false heartwood was investigated relative to the physical and mechanical properties of wood-plastic composites. Birch wood (sapwood and false heartwood) particles were modified with 5 wt% NaOH (by wood content) and 5 wt% 3-aminopropyl-triethoxysilane (by wood content) before being compounded with polypropylene in a co-rotating twin-screw extruder. The compounded composites were then injection moulded into standard test samples. The resulting composites were grouped into four categories: birch sapwood, modified birch sapwood, false heartwood, and modified false heartwood. Neat polypropylene samples were produced as a reference. The samples were tested for their tensile and flexural properties, water absorption, thickness swelling, and ultraviolet aging. The compositions of the composites were analysed using Fourier transform infrared spectroscopy. The results showed that the tensile strength of all of the samples decreased after water absorption. Water absorption decreased the impact strength of all of the composites. Ultraviolet radiation degraded the neat polypropylene and lowered the mechanical properties of all of the composites. Surface chalking was observed in all of the wood-plastic composites exposed to ultraviolet aging, with colours ranging from brown and brownish black to white.

The use of lignocellulosic softwood residues as feedstock for the production of bioethanol and other value-added chemical products has been limited by its high recalcitrance. Alkaline or organosolvent pretreatments have been used to remove recalcitrance in softwoods. Although these methods partially remove lignin and hemicellulose, they also result in low glucose recovery. In the first case, there is low cellulose hydrolizability, and in the second, there is a loss of cellulose. This study evaluated both methods combined into one step: alkaline hydrolysis of the biomass in the presence of an organosolvent. Different conditions of temperature and residence times were assayed. The efficiency of these conditions was quantified as the percentage of lignin and hemicellulose removed from the biomass without loss of cellulose. The substrate produced with the most efficient conditions removed 91% of the lignin and 89.1% of the hemicellulose with no loss of cellulose. Enzymatic hydrolysis of this biomass was 90% to 95%, with a substrate concentration of 3% and with five filter paper units per gram of cellulose (FPU/g cellulose). These results indicated that this one-step alkaline-organsolvent process, applied as a pretreatment to softwood, allows highly efficient lignin and hemicellulose removal. 100% of cellulose was recovered, and there was between 90 and 95% glucose yield after enzymatic digestion.

The inclusion of old newspaper as reinforcement in composites promotes the use of environmentally friendly materials, reduces landfilling, decreases chemical treatments to bleach the recycled paper, and provides alternatives to glass fiber. While there are studies on the tensile strength and stiffness of old newspaper reinforced materials, there is a lack of analysis of their flexural properties. Considering that bending loads are very common, the flexural stiffness of the materials must be examined prior to industrial use. In this study, the flexural moduli of composites made from old newspaper fibers and polypropylene were compared with other composites. The composites showed moduli ranging from 2.1 to 4.1 GPa, and a composite with 50% newspaper content had a flexural modulus comparable to 10% glass fiber composite. These values allow an industrial use of the composites for semi-structural purposes. A method to assess the intrinsic flexural modulus of the reinforcements was presented and evaluated against other micromechanics models. The value of the efficiency factors and a mean orientation angle were also obtained.

A novel miniaturized, transparent reactor system for use as either a research or educational tool was developed for investigating biomass char gasification with oxygen to determine the kinetic parameters. Parametric temperature and pressure data taken can be used to distinguish the validity of assumptions inherent in the Avrami, the random pore (RPM), the unreacted core shrinking (UCSM), and a UCSM hybrid models (HM). The results demonstrate the UCSM for spherical and cylindrical geometries, and an HM variation with a best-fit exponent, that yields residual sums of squares 2 to 4 orders of magnitude lower than other models. An Arrhenius evaluation yielded an activation energy of 84.8 kJ/mol and pre-exponential factor of 1.34  103 s-1. An O2 reaction order of 0.85 indicates O2 adsorption on the char surface is the primary rate-controlling step. Data are consistent with a rapidly decreasing surface area as the reaction nears completion, suggesting available corresponding active sites for rapid chemisorption decrease as the reaction progresses. More importantly, the design of the system is safe to take into the classroom while simultaneously allowing students to view real-time reactions and produce repeatable data; this pushes the bounds on classroom interventions and learning.