Research Articles

Effects of heat treatment on some physical properties of poplar and plane wood specimens were investigated. The main aim was to compare effects of heat on some physical properties of low-density poplar wood and high-density oriental plane wood. Heat treatment was conducted at temperatures of 150 and 200 °C for 3 h in the presence of air at atmospheric pressure. After the heat treatment, the mass loss; oven-dried density; tangential, radial, and volumetric swelling; fiber saturation point; and moisture content were determined. Regression analyses between mass loss and volumetric swelling were performed. The findings were analyzed statistically with ANOVA and the T-test. The results showed that heat treatment at 200 °C influenced the physical properties of both poplar wood and plane tree wood. In addition, the heat treatment had a little greater effect on the swelling and fiber saturation point of poplar wood than it did on the properties of plane wood.

This study investigates the relative ability of natural bamboo fiber used in textile manufacturing to resist attack by bacteria and fungi. These tendencies were determined with the dynamic test method for evaluating antibacterial activity and were compared with the of other textile fibers, such as cotton, jute, flax, ramie, and regenerated bamboo fiber. The bacteria studied were Escherichia coli (8099) and Staphylococcus aureus (ATCC 6538), and the fungal species was Candida albicans (ATCC 10231). The relationships between the bacteriostatic ability of natural bamboo fiber and its physical state, hygroscopicity, and extractives were tested to explore the possible influencing factors. The results show that natural bamboo fiber has no natural antibacterial properties, as compared with natural cotton bacteriostatic rates against the bacteria were all zero. The physical state did not impact the natural resistance of natural bamboo fiber to the bacteria and the fungus. The resistance of the plant fiber may be related to its hygroscopicity, and some extraction methods could improve the ability of natural bamboo to resist microorganisms.

A novel superabsorbent was prepared by utilizing carboxymethyl starch and carboxymethyl cellulose biocomposites as a grafting backbone. The scheme of the CMS-CMC double backbone structure was speculated. It was proposed that the superabsorbent possesses a three-dimensional network with an interpenetrating structure. The response surface methodology was used to optimize the parameters. Interactions among the most influential variables, i.e., the dosage of CMC, the acrylic acid to acrylamide mass ratio, and the neutralization degree of acrylic acid were estimated. A mathematical model was developed, which fit the experimental results well for all of the response variables. The optimal conditions included 28.8 % of CMC dosage, a 1.6 mass ratio of acrylic acid to acrylamide, and 73.4 % of neutralization degree of acrylic acid to achieve 815.2 g/g of water absorbency.

Interest in using kapok (Ceiba pentandra L.)–based cellulose in composite preparation is growing due to its advantages, including cost- effectiveness, light weight, non-toxicity, and biodegradability. In this study, chloroform, sodium chlorite, and sodium hydroxide were used for wax removal, delignification, and hemicellulose removal, respectively. It was observed that the air entrapment inside kapok fiber disappeared after it was treated with alkali. The structure became completely flattened and similar to a flat ribbon-like shape when examined using a vapour pressure scanning electron microscope (VPSEM). Fourier transform infrared (FTIR) spectroscopy was used to characterize the untreated and treated kapok fibers. The peak at 898 cm−1, which is attributed to the glucose ring stretching in cellulose, was observed for the obtained cellulose samples. Peaks corresponding to lignin (1505 and 1597 cm^-1) and hemicellulose (1737 and 1248 cm^-1) disappeared. The results of differential scanning colorimetry (DSC) indicated that the degradation of cellulose appeared as an exothermic peak at about 300 to 350 °C. The activation energy for thermal decomposition of kapok cellulose and its hemicelluloses was 185 kJ/mol and 110 kJ/mol, respectively. The activation energy for thermal decomposition can be used as an alternative approach to determine the purity of cellulose.

Acids and alkalis are considered important catalysts in biomass pretreatment, which is essential to overcome the recalcitrance of lignocellulose for sugar release. In this study, the effects of various chemicals and temperatures on the pretreatment and subsequent enzymatic hydrolysis of wheat straw were investigated. The conversions of glucan and xylan during pretreatment and enzymatic hydrolysis were examined. The temperature and different ions in pretreatment govern the dissociation constant and hydrogen ion concentration. Due to higher dissociation at higher temperature, weak acids and weak alkalis can produce high glucose yields, similar to strong acids and alkalis. The concept of modified combined severity for weak acid pretreatment was explored. The pH value and real combined severity of weak acids at reaction temperatures were estimated according to xylan recovery during pretreatment. Glucose yield in enzymatic hydrolysis is mainly decided by xylan recovery for acidic pretreatment and by total content of xylan and acid-insoluble-lignin in solids for alkaline pretreatment.

Starch microparticles (SM) were prepared by delivering ethanol as the precipitant into a starch paste solution dropwise. Chemically modified starch microparticles (CSM) were fabricated by a reaction with malic acid using the dry-preparation technique. Composites were prepared using CSM and various cellulose materials as fillers within glycerol plasticized–corn starch matrix through the casting process. Microcrystalline cellulose (MC, as reference filler) and two cellulose-enriched materials, namely Asclepias syriaca L. seed hairs (ASSH) and Populus alba L. seed hairs (PSH), were compared in terms of morphology and performance when incorporated within the CSM/S thermoplastic matrix. The effects of cellulose fillers on the morphology, surface, water sorption, and mechanical properties were investigated. The surface water resistance of composite materials was slightly improved through addition of cellulose fillers. Samples containing cellulose fillers presented higher tensile strength but lower elongation values compared with those without fillers.

Aspergillus niger, Penicillam citrinum, and Trichoderma viride were investigated. The results showed that Na-MMT was successfully transformed to OMMT inside WF. Owing to the hydrophobic nature and barrier effect of OMMT on water permeability, the composites showed some improvements in water resistance, dimensional stabilities and antibiotic performance. MMT concentration was also an important factor. The water repellency and dimensional stability were improved with increasing MMT concentration at first and then dropped after the MMT concentration exceeded 0.5%. However, the mold resistance of the composites increased along with increasing MMT concentration. With 1% MMT treated, the mold growth rating decreased to 1 (mold covering of 0-25%). These results suggested that OMMT modified WF had a positive effect on restricting water absorption, swelling, and mold susceptibility for the WF/PP composites.

An attempt was made to chemically modify palm kernel shell (MPKS) to increase adsorption affinity towards Reactive Black 5 (RB5). Granulated palm kernel shell (PKS) was quaternized successfully by treating with N-(3-chloro-2-hydroxypropyl)trimethylammonium chloride under alkaline conditions and was characterized. Surface characterization by Scanning Electron Microscopy (SEM) and BET analysis confirmed the surface pore enlargement from mesospores to macropores after modification. Fourier Transform-Infrared (FTIR) Spectrometer and CHN analysis revealed that the quaternary ammonia group (NR4+) was successfully reacted on MPKS fiber. pH 4 is the optimum for removal of RB5 on MPKS. Equilibrium isotherms were analyzed by the Langmuir, Freundlich, and Redlich-Peterson models. The Redlich-Peterson model was found to fit well with the data. The maximum adsorption capacity of MPKS was 207.5 mg/g for adsorption of RB5.

An ultraviolet (UV)-curable coating is one of the best finishing methods in the paper and packaging industries for protecting ink layers from physical and mechanical defects. The purpose of this study was to investigate the mechanical and optical properties of CMYK printed paperboard after coating it with the UV-curable varnish. Commercial duplex paperboard (glazed grayback paperboard, 230 g/m²) was printed with a CMYK offset printing process. After conditioning the printed samples, they were coated with a commercial UV-curable varnish (consisting of a liquor-to-solvent ratio of 50:50) using an industrial screen-coating machine. The samples were then dried using a UV lamp in an industrial UV drying machine. The discoloration of the CMYK ink layers was measured spectrophotometrically using CIELab parameters (L*, a*, b*, and ΔE) before and after the coating process. The whiteness, brightness, and fold and tear resistance of the ink films were also measured. Color change (ΔE) was recorded for all tested samples, and the least amount of discoloration was observed in CYAN ink. The highest variances of the relative optical parameters were found in the MAGENTA, YELLOW, and BLACK ink films, which resulted in yellowing of the coated paperboard. It can therefore be concluded that the coating process significantly decreased the fold and tear resistance of the samples.

Various chemometric techniques were used to establish the relationship between the autohydrolysis conditions prior to pulping and the chemical compositions of the soluble organic materials removed from Scots pine (Pinus sylvestris) wood chips. The aqueous chip pre-treatments (autohydrolysis) were administered at 130 °C and 150 °C for 30, 60, 90, and 120 min, and the hydrolysates obtained were characterized in terms of total carbohydrates (various mono-, oligo-, and polysaccharides together with uronic acid side groups), volatile acids (acetic and formic acids), lignin, and furans (furfural and 5-(hydroxymethyl)furfural). Based on the analytical data gathered, a relatively accurate model for pine chip autohydrolysis was developed.