Research Articles

Walnut meal and polyethyleneimine (PEI) were used as raw materials for producing an environmentally friendly adhesive to bond plywood, and the shear strength was investigated. The results showed that the walnut meal-based mixture adhesive can successfully be used for the production of plywood. However, the shear strength of plywood clearly changed with different raw materials ratios. Both the wet and hot water strength were improved with increasing polyethyleneimine (PEI) content. This indicated that PEI had an important contribution to the water-resistance of the mixture system, and considering the cost of PEI, a walnut meal powder and PEI weight ratio of 70:30 was recommended. The effects of walnut protein solution thermal processing time and temperature were also studied. It was beneficial to enhance the wet and hot water shear strength of plywood to increase the thermal processing time and temperature. The investigation of curing characteristic of mixture system and monomer ingredient via differential scanning calorimetry (DSC) revealed that the curing peak temperature of the mixture system was similar to PEI, and that a chemical reaction should be made between them during the heating process. Lastly, the thermal characteristic of the mixture system was investigated via thermogravimetric (TG) analysis, where good thermal resistance was displayed.

Wood chip transportation is a widespread practice in Poland, with distances between forest sites and power or heating plants reaching 300 km and truck transport times of up to 6 h. Because the basic parameter affecting biomass quality for energy production is moisture content, the objective of the presented economic analysis was to determine its effect on the price of wood chips transported by semi-trailer trucks. This paper considered the possibility of drying biomass in the semi-trailer. No external energy consumption was envisioned; the heat needed for drying was obtained from the truck cooling or exhaust systems via heat exchangers. The moisture content of transported biomass had a dual effect on the final truckload price. While it increased biomass amount by adding to its weight, it decreased its price by lowering its calorific value. Mathematical analysis showed that a decrease in wood chip moisture content increased truckload price, justifying research on technological improvements of this process. Simulations indicated that by reducing moisture content during transportation, biomass suppliers increased their revenues approximately € 3.6 to € 30.0 per truckload, which translates into annual financial profit ranging from tens of thousands of euros (EUR) to more than € 23,810.

Poplar and black locust plantations are widely used for production of raw materials for biofuel. In this study, the main characteristics affecting energy content were evaluated for 2-year-old plantations obtained from 3 different sites of various qualities were evaluated. The ‘I-214’ poplar and the black locust had smaller (16 to 21%) bark ratios, while the ‘Kopecky’ poplar had a higher (22 to 26%) bark gain yield. The black locust had a higher basic density than that of the poplars, which were wood (446 kg/m3) and bark (402 kg/m3). The higher heating value of the bark of the black locust (19.51 to 19.59 MJ/kg) and of the ‘Kopecky’ (19.58 to 19.86 MJ/kg) was greater than that of the wood; in the case of the ‘I-214’ (19.59 to 19.81 MJ/kg), the higher heating value of the wood was higher. The ash content of the bark (4.50 to 8.22%) was several times greater in the case of poplars and black locust than that of the wood (0.46 to 1.29%). In the case of the wood, the ash content increased by the degradation of the site’s quality. There were remarkable differences between the black locust and the poplars, as well as the individual poplar clones among the main energetic characteristics.

In order to form a firm root plug for the mechanical transplantation, modified urea formaldehyde (UF) resins were applied to bond coir based substrate and form substrate blocks. The physical and chemical structure, thermal stability, and crystallinity of the substrate blocks before and after nursery seedlings were characterized. The results showed that the -NH2 and -OH in the substrate reacted with the modified UF resins to form macromolecular structures. There was almost no difference between the XRD spectra of substrate blocks before and after the growth of seedlings. The modified resins in the substrate block were cured in the form of colloidal particles. The substrate block contained 53.8 At% carbon, 15.0 At% nitrogen, and 23.5 At% oxygen. When compared with the original substrate, the height, stem diameter, root length, and leaf area of tomato seedlings grown in substrate block were improved by 56.1%, 43.3%, 1.3%, and 63.3%, respectively. The qualification percentage of the substrate block was 94.3%, which was well above that of the original substrate (83.4%) according to JB/T 10291 (2013) standards. The substrate block bonded by the modified UF resins was suitable for tomato seedlings growth.

Rice bran was introduced as an alternative nitrogen source to Hestrin and Schramm (HS) medium in HS Acetobacter xylinum culture media in bacterial cellulose (B.C) synthesis. The results indicated an unchanged composition of crude protein per increase in incubation days while diluted protein increased with incubation period. Fourier transform infrared spectroscopy (FTIR) results showed the absorbance of OH groups. It was confirmed that the BC yield was directly proportional to the rice bran content. A general observation indicated a gradual transformation from a highly crystalline structure to a very amorphous structure as rice bran content increased with the endothermic decomposition of samples being recorded between 113.5 °C and 125.6 °C.

Activated carbons (ACs) were obtained from roots of Salvia miltiorrhiza Bunge (Danshen) followed by chemical activation with potassium hydroxide (KOH). The ACs were characterized by nitrogen adsorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and electrochemical testing. Results showed that ACs from cultivation sites in Pingyi (ASPY), possessed many micropores, a dominant amount of mesopores, and few macropores. They achieved a value of 1615 m2/g of specific surface area calculated by the Brunauer-Emmett-Teller (BET) method with numerous oxygen-containing functional groups. Electrodes fabricated with ASPY particles exhibited excellent double-layer specific capacitance (245 F/g), while the other two marked as ASFC (ACs from Fangcheng) and ASZJ (ACs from Zhongjiang) reached values of 163 F/g and 81 F/g, respectively, at a current density of 1 A/g in 6 mol/L KOH electrolytes. Electrodes made by ASPY had a good cyclic stability for 1000 cycles at a potential range from -1 V to 0 V and lower equivalent series resistance (ESR). Meanwhile, the authors found that roots of Danshen that grew in different cultivation sites were remarkably different while they were activated, which was the same with electrochemical properties of the electrodes fabricated by ACs.

Microwave assisted maleic acid (MA) pretreatment is a potential method for biomass processing. The aim of the present study was to determine the optimum conditions for pretreatment of oil palm empty fruit bunch (OPEFB) for bioethanol production, as well as to understand the changes of functional groups in the pretreated OPEFB. The optimum pretreatment conditions with the highest reducing sugar yield (RSY) (47.21%) were 190 °C for 2.5 min with 1% MA. The temperature had more influence on the chemical components and RSY than the other pretreatment parameters. More severe pretreatment conditions tended to dissolve more sugar into the hydrolysates. Structural changes occurred in the OPEFB pretreated with MA and sulfuric acid, which were observed by the absence of certain functional groups. The simultaneous saccharification and fermentation (SSF) of MA-pretreated OPEFB produced ethanol with a concentration of 18.9 g/L and yield of 0.43 g ethanol/g cellulose after pretreatment, or equivalent to 76.6% of theoretical maximum yield. Microwave assisted MA pretreatment of OPEFB successfully increased the RSY about 300% compared to the untreated one. The MA pretreatment removed hemicellulose and lignin. The highest ethanol concentration and yield were produced after 48 h of SSF of the OPEFB pretreated with MA.

Recently, polymer nanocomposites have been fabricated using carbon nanotubes (CNTs) as reinforcement nanofillers. However, the effect of incorporating CNT/polymer into hybrid composites with natural fibre is not clear. This study investigated the effect of using multi-walled carbon nanotube material (MWCNT) as the nanofiller on the tensile and flexural properties of bamboo/glass fibre hybrid composites. Composites containing various weight fractions of CNTs (0.1 wt.%, 0.3 wt.%, 0.5 wt.%, and 1.0 wt.%) were compared with the control hybrid composites. The hybrid composites were prepared with epoxy resin. The experimental results revealed an increase in the tensile strength of the composites with the addition of up to 0.5 wt.% CNTs (+7.7% over the control hybrid). However, beyond this value, i.e., with 1.0 wt.% CNT additives, the composite strength showed a remarkable decrease (-36.8% compared with the control hybrid). Moreover, introducing CNTs into hybrid composites resulted reduced the flexural properties with increasing weight fractions as low as 8.45% compared with the controls. In sum, the tensile properties increased with the addition of up to 0.5 wt.% CNTs, but there was a decrease in the flexural properties.

In terms of manufacturing cost and weight, current bulletproof vests are simply not optimized. This means that consumers and manufacturers alike desire a bulletproof vest that is more user-friendly, cheaper, and lighter. This study considered the tensile and flexural characterization of new lighter and cheaper hybrid composite materials to replace the existing insert panel for the currently available bulletproof vest. The materials chosen included a natural fibre, i.e., kenaf fibre, chemically treated with sodium hydroxide solution, and, as a means of recycling, used x-ray films with a surface treatment. Using the traditional hand lay-up method, the materials were fabricated into seven layers of different configurations, which were then subjected to tensile and flexural tests. The findings showed that one of the configurations that consisted of both treated materials had a tensile strength of 396.9 MPa, which is quite strong, and a flexural modulus of 6.24 GPa, which makes it flexible enough to be made into wearable equipment. This configuration was then chosen to be the base design for the specimen subjected to impact test. The interfacial bond between the two distinct materials proved to be a major issue, even with the help of fibre treatment. Therefore, some improvements need to be made for the material to be comparable to existing materials performance-wise hence making this configuration suitable for ballistic application. However, the design did show promising results by stopping a bullet with speed up to 230 m/s.

A mesoporous carbon as solid acid catalyst was prepared from kraft lignin via one-step phosphoric acid activation. The catalyst was characterized by acid–base titration, N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermal gravity analysis (TGA). The results showed that the prepared solid acid catalyst had high thermal stability, large specific surface area (850 m2/g), and a mesopore structure with the average pore diameter of 4.7 nm. The acid-base titration result of the catalyst revealed high surface acidity (5.36 mmol/g), indicating high catalytic activity. The prepared solid acid catalyst was used to catalyze dehydration of fructose to 5-hydroxymethylfurfural (HMF). The influence of reaction temperature and reaction time on HMF yield was investigated. The results indicated that a HMF yield of 80.1% was obtained with a reaction time of 3 h at 140 °C.