Volume 11 Issue 1

This study investigated the glueless preparation of biomass board using rape straw on a laboratory scale. The board-making process was broken down into four steps: soaking, refining, shape recovery, and hot-pressing. To observe the effect of pressure during the hot-press stage on the strength of the bio-board, five panels were manufactured at various pressures. Moreover, density functional theory (DFT) was used to explore how varying the pressure influenced the strength properties of the board. As pressure increased, the density of these five panels changed from 0.95 to 1.12 g/cm3. The mechanical tests showed that the bending rupture strength of these panels changed from 43 to 53 MPa, while the tensile rupture strength changed from 27 to 33 MPa. The bending strength of these biomass boards performed well enough to qualify them as Type-35 board, and their density classified them as hardboard, according to the Japanese industrial standards (JIS). This study showed that board-making was feasible using rape straw. The experimental results and the density functional theory results were consistent, in that the mechanical properties of the panels improved with increasing pressure. The DFT method was shown to be useful in exploring the factors that influenced the strength properties of the biomass board on the microscopic scale.

Although many studies have been conducted on the wood property and chemical changes caused by thermal modification, little has been reported on the microstructural and topochemical changes occurring in the cell wall during heat treatment. In this study, poplar (Populus cathayaha) was treated within a temperature range from 180 to 220 °C for 4 h. Chemical analyses by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) indicated that heat treatment resulted in deacetylation of hemicelluloses and cleavage of lignin chains, thus generating new carbonyl and phenolic linkages. Transformation of matrix substances contributed to microstructural changes that appeared in clearly distorted and collapsed fiber and vessel walls along with the delamination of compound middle lamella (CML) and secondary walls (S), which showed a reduced capability to resist deformation. It was also observed by fluorescence microscopy (FM) and scanning electron microscope coupled with energy dispersive X-ray analysis (SEM-EDXA) that the concentration of lignin increased, probably because of the degradation of hemicelluloses and the generation of new carbonyl groups. These results on cell wall microstructure and topochemistry can help explain the altered wood properties revealed by dynamic mechanical analysis (DMA) and equilibrium moisture content (EMC) testing after heat treatment.

This study aimed to develop a simple measuring method to determine Young’s modulus of a wooden bar by measuring its flexural vibration without measuring its weight. Before and after bonding an iron piece to a wooden rectangular bar, a free-free flexural vibration test and fixed-fixed flexural vibration test were performed to obtain Young’s modulus. Young’s modulus was calculated by substituting the ratio of the resonance frequencies of a wooden bar with and without a bonded iron piece into the frequency equation. The calculated results resembled the experimental values determined without the iron piece.

Circular moulds, which have multiple holes, are key components of biomass briquetting machines. The configuration parameters of the die holes determine the strength and the service life of the circular moulds. Special testing moulds were designed for this research, and the strain values of the specific points were detected using strain-gauge transducers. Then, the mechanical data of the points, including the positive pressures and the friction and distribution values, were calculated. Mechanical models were established to explore the stress change of the die holes by altering the rheological properties of the straw. In addition, the mechanical models provided the theoretical principles for analyzing their influence on biomass solidification by changing the forming pressure of the die holes during the biomass briquetting process.

With wheat-straw and inorganic binder as the major raw materials, inorganic wheat-straw composite board was manufactured by mold-pressing. The effect of wheat-straw loading on the physical and mechanical properties of inorganic wheat-straw composite board was studied. X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to characterize and evaluate the performance of the resulting composite board. Results showed that the optimal glue-straw ratio was 2.1. With the increase in glue-straw ratio during board maintenance, the inhibition effect was weaker during hydration reaction of inorganic materials. This accelerated the process of the hydration reaction in inorganic wheat-straw composite board such that the reaction was carried out more completely and produced more complete crystallization and more inorganic glue. Internal bond strength (IB) and thermal stability of inorganic wheat-straw composite board increased gradually, while TS decreased. Modulus of rupture (MOR) and modulus of elasticity (MOE) firstly increased and then decreased. In summary, the bonding interface between wheat-straw and inorganic adhesive performed well.

Moisture in wood acting as a plasticizer will strongly affect the wood’s viscoelastic properties. However, achieving the desired moisture content (MC) at elevated temperatures during creep tests is difficult. The aim of this study is to accurately and systematically investigate the creep behavior of birch wood at high temperatures. Experiments were conducted using a dynamic mechanical analyzer with a relative humidity accessory coupled with polyvinylidene chloride (PVDC) film for wrapping samples. Creep behavior was examined at six MCs (0%, 6%, 12%, 18%, 24%, >30%) and 11 temperatures (5 to 105 °C). The MC of wood was strictly and accurately controlled during creep tests. Instantaneous compliance (IC) and creep compliance (CC) increased with the increase of both temperature and MC, with significant changes at higher temperatures and MCs. The effects on IC and CC were more pronounced when the subject was influenced by MC, with readings approximately three times and one time greater than those influenced by temperature, respectively. Dramatic increases in CC were found at certain temperatures and MC values. There was a complex interaction between temperature and MC on IC and CC.

The dissolving properties of softwood in an aqueous solution of the ionic liquid tetra-n-butylphosphonium hydroxide ([P4,4,4,4]OH) were studied. Cedar wood meal and 40% [P4,4,4,4]OH aqueous solution were mixed in a glass tube and treated at 121 °C and 2 atm in an ordinary autoclave. As the treatment time increased, the residue content decreased to 68.7%, 49.4%, and 37.0% after 1, 5, and 20 h, respectively. Following the 20-h treatment time, 97.0% of the residue was determined to be holocellulose and 96.3% of the constituent monosaccharide in the residue was glucose. UV analysis showed that most of the lignin had dissolved in the [P4,4,4,4]OH solution. Phenolic hydroxyl group analysis of the dissolved lignin suggested that the macromolecular structures of the lignin were considerably degraded. The results of this study suggest the possibility of developing a simple multi-sample analysis method for lignin content using a single-step autoclave treatment in a glass tube using an aqueous solution of [P4,4,4,4]OH.

Whole cell biocatalysts for biodiesel production have garnered significant attention in recent years, as they can help avoid the complex procedures of isolation, purification, and immobilization of extracellular lipase. Because of its renewability and biodegradability, loofah (Luffa cylindrica) sponge is an advantageous substitute for traditional biomass carriers in whole cell immobilization. Rhizopus oryzae mycelia can spontaneously attach onto loofah sponge particles (LSPs) during cell cultivation. The highest immobilized R. oryzae cells concentration can reach up to 1.40 g/1 g of LSPs. The effects of biocatalyst addition and water content on methanolysis for biodiesel production were investigated in this paper. The operational stability of glutaraldehyde-treated biocatalyst at 35 °C, using a 1:1 oil-to-methanol ratio, was assayed, revealing a 3.4-fold increase in half-life compared with the untreated biocatalyst. Under optimized conditions, the yield of methyl esters in the reaction mixture reached 82.2% to 92.2% in each cycle. These results suggested that loofah sponge is a potential fungi carrier for an immobilized whole-cell biocatalyst.

Effects of modifying oil palm mesocarp fibers (OPMF) by methacrylate silane on polylactic acid (PLA)/ polycaprolactone (PCL)/clay/OPMF hybrid composites were investigated. The composites were prepared by a melt blending technique and characterized by dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The silane-treated OPMF hybrid composites showed better tensile strength, tensile modulus, and elongation at break than unmodified OPMF hybrid composites. DMA analysis showed an increase in storage modulus when silane-treated OPMF was added to a hybrid composite. The loss modulus curve showed that the incorporation of silane-treated OPMF into a hybrid composite shifted the two glass transition temperatures (Tg) of composites closer to each other. The low tan δ peak indicated good fiber/matrix adhesion for the silane-treated OPMF hybrid composites. SEM micrographs revealed that silane-treated OPMF hybrid composites showed better fiber/matrix adhesion than unmodified OPMF hybrid composites because of absence of gap between silane-treated OPMF and the matrix in the composite.

Regenerated cellulose (RC) biocomposite films from oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were prepared using ionic liquid. N,N-Dimethylacetamide (DMAc) and Lithium Chloride (LiCl) were used to dissolve the regenerated cellulose at room temperature. The effects of OPEFB content and chemical modification using methacrylic acid (MAA) on the X-ray diffraction, tensile properties, morphology, thermal properties, and Fourier transform infrared spectroscopy (FTIR) results for RC biocomposite films were investigated. The chemical modification of OPEFB using MAA enhanced the properties of the treated RC biocomposite films. At 2 wt.% of OPEFB both of the RC biocomposite films showed the highest crystallinity index, tensile strength, modulus of elasticity, and thermal stability. The treated RC biocomposite films had a higher crystallinity index, tensile strength, modulus of elasticity, and thermal properties than the untreated RC biocomposite films. The Tdmax of treated RC biocomposite films with MAA was higher than that of untreated RC biocomposite films. This indicates that treated biocomposite films had higher thermal stability. The enhancement of interfacial interaction and the dispersion of treated RC biocomposite films with MAA were revealed by scanning electron microscopy (SEM). The FTIR spectra of treated RC biocomposite films indicated interaction between cellulose from OPEFB and MCC with MAA.