Research Articles

This study investigates the influence of carbon black from carbonized Jatropha seed shell as a filler that was obtained by furnace method at 600 °C on the material properties of vinyl ester based biocomposites. The biocomposites were characterized for mechanical, thermal, and morphological properties. The tensile strength was enhanced at 10 wt.% loading of filler material as compared to the virgin polymer and higher loading percentage. Flexural strength decreased with an increase in the carbon black loading percentage, while the tensile modulus and flexural modulus showed an opposite trend. Thermogravimetric analysis showed enhancement in the residual content of the composite materials, thereby ameliorating thermal stability. Glass transition and melting temperatures by DSC analysis were observed to increase up to 10 wt % loading of filler but to decrease subsequently at higher loading percentage. The morphological analysis showed smooth morphology with intermittent lumps of agglomeration at higher loading percentages.

Oil palm wood (OPW) is still difficult to utilize efficiently due to its low strength, non-durability, low dimensional stability, and poor machinability. This study was conducted to investigate semi-curing of OPW with low-molecular weight phenol formaldehyde (Lmw-PF) by a combination of oven and microwave heating. Four main processes in a modified compreg method were used, i.e. drying, impregnation, resin semi-curing heating, and hot-pressing densification. Heating type had a significant effect on the physical properties of treated OPW. The combination of the heating methods used a much shorter time compared to heating by oven only, where over 24 to 30 h were needed to dry the treated OPW.

In this study, the effect of an atmospheric-pressure plasma treatment on the surface properties of sugar maple (Acer saccharum March.) and black spruce (Picea mariana (Mill.) was analyzed by contact angle measurement and a water-based coating pull-off testing. The plasma gases used were Ar, N2, CO2, and air. It was found that the wettability with water and the coating adhesion of maple and spruce can be highly influenced by the nature of the plasma gas used and the plasma treatment time. For example, in the case of sugar maple, coating adhesion increased by 66% after 1.5 s of exposure to argon plasma. Repetition of the contact angle measurement one and two weeks after the initial plasma treatment showed that the plasma-induced modification is not permanent. Improvements in wettability and adhesion were also obtained with simpler, cheaper air plasmas, a result promising for the development of advanced plasma reactors operating at atmospheric pressure, specially designed for the wood industry.

Natural fiber is a renewable resource characterized by its low cost and environmental friendliness. However, flame retardant properties are one of the biggest limitations for the preparation of composite materials that need to be improved. In this work, a novel complex flame retardant consisting of aluminum hydroxide (ALH) and decabromine diphenyl oxide (PBDE) was proposed to inhibit the thermal decomposition. Flame-retarding paper was made from softwood pulp and complex flame retardant. The thermal properties of the flame retardants were studied using thermogravimetric analysis (TGA). The mechanical properties of paper treated at different temperatures were tested, while the surface characteristics of natural fiber were detected by a scanning electron microscope (SEM) and atomic force microscope (AFM); their specific surface areas were also measured. The optimum value of aluminum hydroxide to decabromine diphenyl oxide was 3 to 1, added at 70% based on dried natural fiber. It also had good flame retardant performance and mechanical properties at 200 °C for 5 min; meanwhile, the tensile index of the handsheet was 82.5 Nm/g, and the specific surface area was 0.414 m2/g.

Plywood samples treated with ammonium polyphosphate (APP) and 4A zeolite were prepared to investigate the effect of zeolite on wood’s burning behavior using a cone calorimeter under a heat flux of 35 kW/m2. Results showed that APP decreased the heat release rate (HRR), total heat release (THR), and mass loss rate (MLR) of treated plywood. However, APP significantly increased the total smoke release (TSR) and carbon monoxide (CO) yield. The addition of 4A zeolite reduced the HRR, peak HRR, and THR of the plywood treated with only APP. The second HRR peak in a typical plywood curve diminished with the addition of as little as 2% 4A zeolite. The average specific extinction area (ASEA) and CO yield decreased significantly with the presence of zeolite in the APP. The ignition time did not change significantly and the TSR increased when zeolite was present. Thus, a suitable amount of 4A zeolite works synergistically with APP in promoting flame retardancy in flame retardant plywood.

Cornstalk cellulose was liquefied in sub- and supercritical ethanol using an autoclave at 320 °C with 160 mL of ethanol. The effects of reaction time on esters formation during cellulose liquefaction were investigated. The yield of esters was 10.0% at 30 min, increasing to 19.1% after 60 min. Ethanol favored esters formation from cellulose liquefaction. The liquid products at different reaction time were analyzed by FT-IR and GC/MS. The results showed that many free radicals were produced in sub-/super-critical ethanol interactions. Cellulose was converted to active cellulose, which was transformed into large molecular acids by dehydration, decomposition, ring-opening reactions, isomerization, and aldol condensation, and then formed ethyl esters such as ethyl lactate by esterification. In addition, ethyl esters were decomposed to acids, alcohols, and other compounds with increasing reaction time in the presence of ethanol free radicals. Using these results, a reaction network for the formation of ethyl esters from cellulose in sub- and supercritical ethanol was proposed.

Autohydrolysis pre-treatments were performed for the production of hemicellulose-rich autohydrolysates from silver birch (Betula pendula) chips prior to chemical pulping. Pre-treatment conditions were varied with respect to time (from 30 to 120 min) and temperature (130 and 150 °C), covering a P-factor range from 10 to 238. Hydrolysates were analyzed in terms of carbohydrates, lignin, volatile organic acids, and furanoic compounds. The analytical data were subjected to various chemometric techniques to establish the relationships between dissolved organic components, hardwood and softwood used in the experiments, and applied pre-treatment conditions. Using this method, differences between the wood species could be clearly seen, and a relatively accurate model for the autohydrolysis of birch chips was developed.

A crosslinked chitosan membrane (I) and a hydroxymethylated lignin-chitosan crosslinked membrane (II) were prepared using glutaraldehyde as the crosslinking agent. Fourier transform infrared spectroscopy (FTIR) was used to identify the chemical structures of the crosslinked membranes and the presence of an absorption peak at 1515 cm^-1 indicated the presence of lignin. Scanning electron microscope (SEM) images revealed that membrane (I) possessed a smooth surface, while membrane (II) exhibited a homogeneous embossed surface without any agglomeration. The Cu(II) ion adsorption properties of both membranes were analyzed. The results indicated that the static adsorption capacities of membranes (I) and (II) were 195 mg Cu(II)/cm² and 275 mg Cu(II)/cm², respectively, and their dynamic chelation capacities were 2.89 mg Cu(II)/cm² and 4.59 mg Cu(II)/cm², respectively. Membrane (I) was suitable only for use in aqueous solutions with pH values of 3.5 to 9.0, while membrane (II) maintained its shape even in concentrated hydrochloric acid or 1 M NaOH solution. The Cu(II) ion absorption properties and resistance to acid and alkali of membrane (II) were superior to those of membrane (I), indicating that hydroxymethylation of the lignin-chitosan crosslinked membrane is worthy of further investigation.

Peanut shell char (PSC) was converted into active carbon monoliths (ACMs) by adding a binder that was easy to make. The conversion process involved adding the PSC into H3PO4-loaded sawdust, extruding the mixture, and finally heating the resulting monoliths for different times. The properties of the resulting ACMs were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared analysis, nitrogen adsorption-desorption, X-ray diffraction, and thermogravimetric analysis. The H3PO4-loaded sawdust could be used as a binder for converting powdered PSC into well-shaped ACMs without visual cracks. The resulting ACMs maintained their monolithic shape, even in water. The ACMs showed a much higher specific surface area (SSA, 850 to 915 m²/g) than the PSC (105 m²/g). The largest SSA (915 m²/g) was achieved by activation for 50 min. Increasing the activation time decreased the SSA and apparent density, but only slightly impacted the carbon structure. This research might lead to value-added conversion of bio-chars.

A comprehensive process was developed to make full use of the solid and liquid products during the production of activated carbon. Almond shell waste was modified with phosphoric acid and thermally treated to give activated carbon. Wood vinegar was generated and collected within the temperature range of 90 to 500 °C, and the maximum amount of the wood vinegar was in the range of 170 to 370 °C, which also gave the strongest anti-pathogens activities with the lowest pH and the highest organic acid content. The remaining residue after wood vinegar generation was further calcined in inert atmosphere to obtain high surface area activated carbon. The pre-treatment of almond shell with H3PO4 leads to the higher surface area, but H3PO4 solution with concentration more than 40% does not increase the surface area further. The impregnation of H3PO4 helps the formation of pores in the almond shell during the calcination, and gives higher iodine number and methylene blue sorption capacity of the resultant activated carbon materials.