Volume 11 Issue 4

Sound absorption coefficient of oil palm trunk was explored using an impedance tube. Palm samples were taken from the central part of oil palm trunks with cut directions parallel and perpendicular to vascular bundles. Sound absorption was evaluated for palm panels with blind-holes with multiple radii and depths, as well as perforated and grooved panels and a panel with perforated holes at different distances from a solid backing. Measurements of sound absorption within the frequency range of 300-2000 Hz indicated that the sound absorption coefficient of the cross-cut biomass, ~0.15, was slightly greater than that of the parallel-cut panel, ~0.10. Samples with different depths of blind holes showed slight improvements in sound absorption coefficients as compared to the unmodified cross-cut panel. There was a significant improvement for 5-mm hole diameter with 10-mm depth, ~25% improvement as compared to that of 5-mm depth. The combination of the through-hole panel and grooved board allowed ~80% of sound to be absorbed for 1750 to 2000 Hz. Finally, the grooved board was removed and an air cavity backing was introduced by placing the through-hole panel 2-, 4-, and 6-mm away from the tube end. The sound absorption coefficients were then measured to be greater than 80% near the resonance frequencies, as calculated using the distributed Helmholtz resonator model.

Bamboo is used as a raw material for producing chopsticks, artifacts, utensils, plywood, fiberboard, and decorated multi-layered panels. The manufacturing process generates a large amount of bamboo residual waste. In this study, bamboo-derived fuels were prepared from the residual waste of Dendrocalamus latiflorus, Phyllostachys makinoi, and Phyllostachys pubescens. The combustion behaviors of bamboo-derived fuels were also investigated. The characteristics of derived fuels made from bamboo waste with engine oil waste showed that the ash content was less than 5% and that the calorific value reached 5,000 kcal/kg, which was higher than derived fuels standards. Additionally, the derived fuel of bamboo waste had a high combustion efficiency and low nitrogen, sulfur, and chlorine emission levels, which were lower than the derived fuels standards. Thus, bamboo-derived fuel prepared from Dendrocalamus latiflorus, Phyllostachys makinoi, and Phyllostachys pubescens waste mixed with engine oil waste is a suitable fuel alternative.

The physico-chemical properties of lignin isolated from lignocellulosic bioethanol residues and hardwood kraft black liquor were compared with two commercial lignins, kraft softwood lignin, and soda non-wood lignin. Lignin from the industrial residues was isolated through the acid precipitation method. The amount of lignin isolated was approximately 38% of the dry weight of lignocellulosic bioethanol residues and approximately 27% of the black liquor solids. The numbers of methoxyl groups and phenolic and aliphatic hydroxyls were determined to derive a molecular formula for each of the four lignins. The molecular weights of the lignins were measured by high performance size exclusion chromatography. Potential value-added applications of the lignins were summarized based on their molecular weights and physico-chemical characteristics.

Deep eutectic solvents (DESs) offer attractive options for the “green” dissolution of cellulose. However, the protic hydroxyl group causes weak dissolving ability of DESs, requiring the substitution of hydroxyl groups in the cation. In this study, a novel allyl-functionalized DES was synthesized and characterized, and its possible effect on improved dissolution of cellulose was investigated. The DES was synthesized by a eutectic mixture of allyl triethyl ammonium chloride ([ATEAm]Cl) and oxalic acid (Oxa) at a molar ratio of 1:1 and a freezing point of 49 °C. The [ATEAm]Cl-Oxa exhibited high polarity (56.40 kcal/mol), dipolarity/polarizability effects (1.10), hydrogen-bond donating acidity (0.41), hydrogen-bond basicity (0.89), and low viscosity (76 cP at 120 °C) owing to the π-π conjugative effect induced by the allyl group. The correlation between temperature and viscosity on the [ATEAm]Cl-Oxa fit the Arrhenius equation well. The [ATEAm]Cl-Oxa showed low pseudo activation energy for viscous flow (44.56 kJ/mol). The improved properties of the [ATEAm]Cl-Oxa noticeably promoted the solubility (6.48 wt.%) of cellulose.

High-fiber-content composites made from rice husk (RH) (from 50 up to 80 wt%) as well as a recycled thermoplastic blend (rTPB) were fabricated using a two-step extrusion and hot/cold press molding technique. The temperature dependency of the thermal degradation and dynamic-mechanical behavior was investigated using thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The long-term water absorption and orthotropic swelling were analyzed following immersion in distilled, tap, and sea water for 15 weeks. Improvements in the thermal stability, storage, and loss modulus, as well as reductions in dimensional stability, were observed as the alkali content of the RH in the rTPB composites was increased. The composites immersed in sea water showed the lowest water absorption, followed by those in distilled and then tap water. The thickness dimension of the composite specimens exhibited the highest swelling values, followed by width and then length dimensions. The tensile strength and elastic modulus showed the maximum values at 70 wt% RH (21.2 MPa and 1.6 GPa, respectively). The surface morphology, interfacial adherence, and bonding between the matrix-fiber phases in the composites were characterized using a scanning electron microscope (SEM).

Cellulose-based materials are good alternatives to petroleum-based materials in the packaging industry, considering their sufficient mechanical properties and sustainability; however, the barrier performances of cellulosic packaging materials against water and water vapor are generally poor due to the hydrophilic nature of cellulose. In this study, a soybean oil-based polymer was synthesized on the surface of several cellulosic materials through an acrylated-epoxidized soybean oil (AESO) reactive coating. The best conversion of the reaction was observed when a suitable reaction temperature, curing time, initiator dosing, and monomer content were selected. Five different types of cellulosic packaging materials were used as substrates for the reactive coating, and their barrier performances were investigated. The improvement in water barrier properties was indicated by the change in water droplet contact angle (CA). The water vapor permeability (WVP) of the substrates was reduced significantly after coating. The water vapor barrier properties of the coating were highly dependent on the tested substrate. A comparison of CA and WVP showed that the change in water vapor barrier did not correspond to surface hydrophobicity.