Research Articles

This study focuses on the development of epoxy/luffa composites and the investigation of their mechanical and acoustical properties. The fibers underwent an alkalization treatment, and its effects on the mechanical and sound absorption properties of the composites were measured utilizing a universal testing machine and two-microphone transfer function impedance tube methods. The effects of chemical modifications on the fibers were studied using a scanning electron microscope (SEM). The thermal analyses of composites were conducted using thermo-gravimetric analysis (TGA). The composite’s functional group was identified and evaluated using Fourier transform infrared spectroscopy (FTIR). The sound absorption coefficient of untreated and treated composites across a range of frequencies was very similar. Untreated composites appeared to perform better than those that were treated. Compared with untreated fiber composites, there was an improvement in the tensile strength of the treated fiber composites. The SEM characterization showed that the alkaline treatment changed the morphology of the fibers, resulting in a decrease in the sound absorption coefficients of the composites. The thermal characterization of composites showed that dehydration and degradation of lignin occurred in a temperature range of 40 to 260 °C, and the maximum percentage of cellulose was found to decompose at 380 °C.

Fully degradable poly(L-lactic) acid (PLLA) and lignin blends were prepared using the melt blending method. The impact strength of PLLA was dramatically improved by 52.4% and 36.6% with the addition of 5 wt% and 10 wt% of lignin, respectively. Meanwhile, the Young’s modulus was maintained. Polarized optical microscopy (POM) results indicated that lignin served as a nucleating agent for the heterogeneous crystallization of PLLA in blends, which was responsible for the improvement in the impact strength. The introduced lignin also promoted the cold-crystallization of PLLA, which was demonstrated by differential scanning calorimetry (DSC). The blends of PLLA with lignin are considered to be a promising material because of the improved toughness, the full degradability, and the lower price compared with pure PLLA.

In this study, three different sealants (gelatinized starch (GS), gelatinized starch/wood flour mixture (GSWF), and soy-protein adhesive (SPA)) were used to seal the lathe checks in veneers before applying phenol formaldehyde adhesive. The shear strain distribution on the interphase of the lap joint specimens was measured by a digital image correlation technique. The results showed that the average shear strain along the bond line on the interphase was 1.94×10^-3 when the specimen had lathe checks. Sealing treatment can thus reduce the average shear strain effectively. Soy-protein adhesive seemed to have the greatest ability to decrease the average shear strain along the bond line, from 1.94×10^-3 to 0.94×10^-3. In contrast, gelatinized starch appeared to decrease the strain slightly to 1.61×10^-3. Average shear strain along the bond line of specimens treated with gelatinized starch/wood flour mixture was 1.00×10^-3, which was between the values of the other two sealants. Dry shear strength of samples treated by GS and SPA increased from 7.6 MPa to 9.65 MPa and 8.85 MPa, respectively. The mixture of GSWF decreased the strength to 6.32 MPa. Wet strength of treated samples were smaller than untreated ones.

Ganoderma lucidum has a well-developed ligninolytic enzyme system, where laccase is the dominant and sometimes only synthesizing enzyme, and therefore could find an application in the delignification of abundant plant raw materials and in food, feed, paper, and biofuel production. The questions that provided the goals for the present study were whether the profile of G. lucidum laccase depends on cultivation type and carbon source, as well as whether intraspecific diversity exists. Conditions of submerged cultivation proved more preferable for laccase activity compared with solid-state cultivations in all studied strains, while oak sawdust provided a better carbon source than wheat straw. Maximum laccase activity (7241.0 U/L) was measured on day 14 of oak sawdust submerged fermentation by strain BEOFB 431. Intraspecific diversity in synthesized proteins was more significant in wheat straw than in oak sawdust submerged fermentation. The profile of laccase isoforms was dependent on strain, plant residue, type, and period of cultivation. Four acidic laccase isoforms (pI 3.6) were detected in G. lucidum BEOFB 431 at the same cultivation point where maximal enzyme activity was measured.

This work analyses the anti-fungal efficacy and stability of 10 essential oils, as well as their colour stability, in wood. The efficacy of oils against the decay fungi Coniophora puteana and Trametes versicolor as well as the moulds Aspergillus niger and Penicillium brevicompactum was evaluated first on filter papers treated with 1, 3.5, 10%, or 100% concentrate, and then on beech wood treated with 10% solutions. Accelerated ageing of treated beech samples was done before mycological tests and consisted of heating, leaching followed by heating, and Xenotest followed by heating. The highest growth inhibition of moulds and C. puteana was caused by thyme, oregano, sweet flag, and clove oils, while the savory and birch oils were less effective. These oils are potentially useful for wood protection against brown-rot fungi and moulds, mostly in interior conditions. The essential oils had only a negligible effect against the white-rot fungus T. versicolor, which was more apparent after previous ageing of wood. Some essential oils with a yellow tone (birch, oregano, sweet flag, savory, and tea tree oils) significantly changed (p<0.05) the natural colour of beech wood, but the new colours were relatively stable and underwent only mild changes after accelerated ageing in Xenotest.

In this paper, a kinetic model of the first chlorine dioxide bleaching stage (D0) in an elemental chlorine-free (ECF) bleaching sequence is presented for bagasse pulps. The model is based on the rate of adsorbable organic halogen (AOX) formation. The effects of the chlorine dioxide dosage, the sulfuric acid dosage, and the reaction temperature on the AOX content of wastewater are examined. The reaction of AOX formation could be divided into two periods. A large amount of AOX was formed rapidly within the first 10 min. Ten minutes later, the AOX formation rate significantly decreased. The kinetics could be expressed as: , where W is the AOX content, t is the bleaching time (min), T is the temperature (K), is the dosage of chlorine dioxide (kg/odt), and is the dosage of sulfuric acid (kg/odt). The fit of the experiment results obtained for different temperatures, initial chlorine dioxide dosages, initial sulfuric acid dosages, and AOX content were very good, revealing the ability of the model to predict typical mill operating conditions.

Co-gasification of biomass (rice straw) and polyethylene (PE) was conducted in a lab-scale entrained-flow gasifier. The influences of PE proportion, reaction temperature, and equivalence ratio on producer gas composition, gasification index, and tar yield were investigated. In addition, the effects of dolomite and ) catalysts on the co-gasification process were also examined. Increased PE proportion led to an increased lower heating value (LHV) of producer gas as well as an increase in tar yield. In addition, a higher reaction temperature could improve both gas quality and gasification indices significantly. An equivalence ratio (ER) of 0.25 led to a relatively high LHV and low tar yield. Na2CO3 showed a better tar removal efficiency than dolomite. Dolomite increased the LHV of producer gas, while Na2CO3 decreased the LHV. The difference in the catalyst proportion did not cause any significant change in the gas composition and gasification indices. The producer gas with the highest LHV and lowest tar yield was obtained by the co-gasification of 80% (w/w) straw, 20% (w/w) PE, and 3% (w/w) dolomite.

Syngas from biomass gasifiers contains impurities such as tars and particulates, which can create difficulties for the downstream processes (e.g., internal combustion engines and the Fischer-Tropsch process). To design an efficient and effective gas cleaning system, it is important to accurately quantify the tars and particulates. The absence of an ASTM procedure for tars and particulates produced from a gasifier led to the development and testing of the protocol presented in this study. Syngas was generated from woodchips using a pilot-scale downdraft gasifier, which was designed and constructed in-house. The sampled impurities were analyzed using mass gravimetry, solvent evaporation, and weight differential methods. The higher heating value of the exiting gases was estimated from the syngas composition. The average tar and particulate concentrations of the sample runs were 1.8 to 3.1 g/m³ and 5.2 to 6.4 g/m³, respectively. The higher heating values of the syngas ranged between 4.38 and 4.55 MJ/m³.

The utilization of kapok husk (KH) as a reinforcing filler can enhance the properties of soy protein isolate (SPI)/kapok husk (KH) films. The properties of soy protein isolate/kapok husk films with and without the cross-linking agent glutaraldehyde (GLA) were investigated. Films with different KH contents were prepared through a solvent casting method. The addition of KH to SPI films increased the tensile strength, modulus of elasticity, and thermal stability, but reduced the elongation at break. The presence of glutaraldehyde improved the tensile and thermal properties of SPI/KH films. The tensile strength of modified SPI/KH films at 40 wt% increased by 30% compared to unmodified films. The improvement of interfacial interaction between the KH and SPI was demonstrated using a morphology study. Fourier transmission infrared spectroscopy (FTIR) analysis indicated the presence of ethylenic (C=C) groups and imine (C=N) groups. An enzymatic degradation test of SPI/KH films was performed for 14 days in a diatase buffer solution at 37 °C. The enzymatic degradation weight loss of unmodified films decreased with increasing KH content. In contrast, the modified SPI/KH films with glutaraldehyde retained about 50% of their original weight.

Pretreating bamboo is essential to overcome the recalcitrance of lignocellulose for bioethanol production. In this study, the effectiveness of formic, acetic, and sulfuric acids in pretreating bamboo were compared. To measure pretreatment efficiency, the enzymatic digestibility of the pretreated bamboo substrates was determined. Monomeric glucose conversion yield was measured after enzymatic hydrolysis. Additionally, the sugar degradation products fermentation inhibitors were measured after pretreatment. After conducting many tests, it was determined that pretreatment with dilute formic acid at 180 °C and 30 min can be an acceptable alternative to dilute sulfuric acid pretreatment.