Research Articles

Activated carbon, graphite, and GO/gelatin composite films were prepared by the blending method. The properties of composites were characterized by tensile strength (TS), elongation at break (EB), water vapour permeability (WVP), water-absorption ability, contact angle, scanning electron microscopy (SEM), and moisture at different temperatures. The properties of GO/gelatin composite films were better when each of three kinds of carbon materials were used as reinforcement phases and added into the matrix gelatin. The results showed that EB and TS of GO/gelatin composite films were both excellent. The moisture of GO/gelatin composite films was greater than the others. SEM micrographs showed that GO had better compatibility and dispersibility with gelatin than activated carbon and graphite. The water absorption of GO/gelatin composite films were low, at 15 °C and 25 °C, and the WVP was low at 35 °C. The WVP of GO/gelatin composite films was lower than the others at different temperatures. The contact angle of GO/gelatin composite films was larger than the others.

A shape-stabilized composite phase change material (SCPCM) made of n-nonadecane infused by capillary forces in a compressed reduced graphene oxide-activated carbon matrix (EFB(rGOAC)-M) was prepared from oil palm empty fruit bunch. The composite exhibited improved thermal properties and was used to fabricate an SCPCM by impregnation, in which the pores of the EFB(rGOAC)-M served as the support, while n-nonadecane was the central envelope. The EFB(rGOAC)-M exhibited a specific surface area of 680 m2 g-1 and an average pore size of 22 Å. The successful infiltration of n-nonadecane into the pores of EFB(rGOAC)-M was confirmed via nitrogen gas adsorption-desorption isotherms and scanning electron micrographs. According to the differential scanning calorimeter analysis, the composite SCPCM-5 exhibited melting and freezing temperatures of 37.25 °C and 25.58 °C, respectively, and an associated latent heat value of 82.72 J g-1 and -62.22 J g-1, respectively. There was no seepage during the phase change process (from solid to liquid, as the n-nonadecane was uniformly dispersed in the pores of the carbon matrix (EFB(rGOAC)-M) and held by the capillary and the surface tension forces of the carbon matrix. This innovative, inexpensive and environmentally friendly shape-stabilized phase change material could be applied for thermal energy storage applications.

The potential of broom biomass to produce oligo- and monosaccharides was investigated using mild sulfite pretreatment conditions followed by enzymatic hydrolysis. Both treatments were analyzed via response surface methodology using an experimental central composite rotatable design 24 + star, which explored the following variables: sulfuric acid charge (0% to 3%), sodium sulfite charge (0% to 4%, maximum temperature (150 °C to 190 °C), and time at maximum temperature (0 min to 30 min). Oligo- and monosaccharides in the pretreatment hydrolysates were determined using high performance liquid chromatography. The amount of total extracted xylose, mannose, and galactose ranged from 3.5% to 15.8% of the initial biomass, while the model estimated optimal reaction conditions enabled the extraction of practically all hemicellulose in the raw material. However, the mildest pretreatment reaction conditions, with low temperature and low sulfuric acid charges, provided a hydrolysate where a major part of the extracted polysaccharides remained in oligomer form, enabling their separation by filtration. The cellulose-rich solid residue was submitted to enzymatic hydrolysis using a Novozymes® enzymatic cocktail. The enzymatic hydrolysis was successful, but some polysaccharides remained in the solid residue, mainly composed of lignin. An enzymatic yield of 60% was attained with no added sulfite in the pretreatment at 190 °C, despite the confirmed positive role of sulfur content in the solid residues.

Compression of alfalfa into briquettes is an effective way to solve the problem of storage and transportation. In the process of compression, heat is generated and the temperature is raised in the material. In fact, the appropriate temperature can improve the quality of alfalfa briquettes and reduce the energy consumption of densification. In this study, the effect of assisted vibration on the compression temperature was tested. The results showed that when the vibration frequency was below 15 Hz, the temperature at the center and side in compressed alfalfa increased slowly with compression time. When the vibration frequency was above 20 Hz, it increased first and then decreased with the increase of time. Moreover, the maximum temperature value increased remarkably when the frequency was above 20 Hz. In the same vibration frequency and compression time, the center temperature in the compressed alfalfa was higher than the side temperature. The experimental results provide a reference for the determination of reasonable vibration parameters, and explanation of the effect of vibration on reducing energy consumption.

A high-speed milling experiment on wood-plastic composites was performed using cemented carbide tools, and the resulting wear pattern was studied. The influence of the cutting parameters, the cutting speed, feed speed, and axial cutting depth on the tool wear was studied via response surface methodology, and the influence of the interaction of the cutting parameters on tool wear was analyzed. Three-dimensional surface graphs and contour plots of the tool wear results were established. According to the experimental results, a mathematical model of the tool wear based on the second-order response surface methodology was established, and the model was utilized to verify its feasibility. The results show that the nose width (NW) increases with the increase of the cutting speed and axial cutting depth and decreases with the increase of feed speed. Among the factors affecting tool wear, the cutting speed had the greatest influence, followed by the feed rate, with the axial cutting depth affecting tool wear the least. According to the results of the interaction between the tool wear and the cutting parameters, a low feed speed and small axial cutting depth can be selected to ensure long tool life; for low-speed cutting, a high feed speed and large axial cutting depth can be adopted to ensure tool life while improving machining efficiency.

Oleoresin from Pinus merkusii is one of the most important forest products in Indonesia. The objective of this study was to examine the effects of various stimulants and environmental factors on oleoresin yield. The first factor was the stimulant treatment, i.e., SAEt1 (20% sulfuric acid + 1% Ethephon); SAEt2 (20% sulfuric acid + 2% Ethephon); SR4 (mainly composed by sulfuric acid); ETRAT (mainly composed by ethylene and citric acid); and without stimulant spraying. The second factor was the site with different altitudes, i.e., West Banyumas (326 m asl), East Banyumas (797 m asl), and West Pekalongan (1150 m asl). Through analysis of variance, the relation between stimulant and site was highly significant in regards to the average daily oleoresin yield. The results indicated that the combination of sulfuric acid and Ethephon increased oleoresin production 1.69- to 2.85-fold compared with untreated trees, depending on the sites. The trees with SAEt1 and SAEt2 treatments yielded an equivalent amount of oleoresin compared to that of trees exposed to the SR4. The ETRAT showed the lowest resin yields compared to the other stimulants. The values of daily relative humidity and temperature did not show similar responses in all sites when correlated with daily oleoresin yield.

Agarwood (Aquilaria crassna) (ACW) waste is widely available as a by-product of agarwood essential oil production. In this study, ACW waste was ball milled into ACW powder (passed through 120 mesh) and used as filler in natural rubber latex foam (NRLF) prepared by the Dunlop method. The effects of the ACW filler on cell morphology and properties of the NRLF were determined. It was found that the ACW filler loading affected cell morphology of the NRLF. The cell size of the ACW-filled NRLF increased with ACW loadings of 1.5 parts per hundred parts of latex (phr) and 2.5 phr, compared with that of control NRLF. A bimodal cell size distribution (with large and small cells) was dominant in the ACW-filled NRLF at loadings of 3.5 phr, 4.5 phr, 5.5 phr, and 6.5 phr. The cell walls also became thicker, causing inferior compression set behavior. In addition, the density and hardness of the ACW-filled NRLF increased with ACW filler loading.

KHSO4 was used for furfural production, and the catalyst was recovered. The wet solid mixture after reaction was subjected to hot water washing and solid-liquid separation to recover the catalyst into the filtrate. Methods for determination of the catalyst content in both liquid and solid phases were invented. The effect of the mass ratio of hot water to the wet solid mixture, washing time, and number of washing times on the catalyst recovery were investigated. The total recovery of the catalyst into the filtrate was up to 87.7% when using the optimum conditions. The catalyst was reused in laboratory experiments up to 5 successive times. The recovered catalyst had the same activity for furfural production as the fresh catalyst on the same dosage level. Thermal gravimetric and X-ray diffractometer analyses of the catalyst showed that the catalyst was stable and reusable.

Fibrillated cellulose has been frequently used for making nanopapers and thin films. However, limited work has been carried out in the construction of such materials using native lignocellulosic biomass. Making papers from fibrillated biomass allows complete utilization of whole plant material and may reduce chemical and energy consumption. Ultra-friction grinding was used to directly fibrillate knife-milled poplar into micro- to nano-sized biomass fibers. Papers were made using the fibrillated biomass containing nanofibrillated biomass and their mechanical properties were tested. Biomass papers made via press-drying had higher tensile strength than papers made by air-drying. A higher press-drying temperature of 180 °C produced stronger papers than at 150 °C. Guar gum substantially increased the strength of the press-dried papers in comparison to cationic starch. Press-drying increased the thermogravimetric peak decomposition temperature by 13 °C in comparison to air-drying.

Nickel catalyst supported on honeycomb cinder (Ni/HC) was prepared by a homogeneous precipitation method. The catalyst was applied to produce hydrogen-rich combustible gas by catalytic pyrolysis of soybean straw and plastic (PE) mixture. The straw and plastic materials were analyzed by elemental analysis and industrial analysis. The support and catalyst were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2 adsorption-desorption isotherm (BET). The analysis showed that NiO was well loaded on the surface of honeycomb coal slag carrier. The effects of Ni loading, pyrolysis temperature, holding time, and calcination temperature on the experimental results were studied. The results showed that the preparation of the catalyst was feasible and that it had a good catalytic effect. When Ni loading was 15 wt.%, catalytic pyrolysis temperature was 700 °C, holding time was 20 min, and calcination temperature of catalyst was 400 °C, H2 concentration increased from 20.6 to 52.8 vol.%, and while H2 yield was 302 mL/g, CH4 concentration decreased from 51.1 to 22.6 vol.% and CO concentration increased from 10.8 to 17.8 vol.%. After the catalyst was regenerated 6 times, the H2 concentration still reached 40 vol.% and the combustible gas concentration was still above 80 vol.%. The catalyst still had good catalytic activity.