Research Articles

There are health and safety risks involved in the production and storage of forest biomass. Fungi that are formed in the stored piles of wood chips pose a high potential risk for human health. Three experimental piles, containing wood chips from three species of trees, were created. They included European beech (Fagus sylvatica), common aspen (Populus tremula), and European spruce (Picea abies). The piles created were in the shape of a pyramid with the base measuring 4 m x 4 m. In each pyramid, 3 points of measurements were established at 0.5 m, 1.0 m, and 1.5 m above the ground. Temperature, relative moisture, and the number of microscopic fungi colonies were monitored at each point of measurement in the period between 13th December 2011 and 6th June 2012. The highest relative moisture content was recorded in the pile with the European spruce. The aim of the experiment was to identify the genus and species of fungi that are formed in the chip piles during long-term storage and which pose a potential risk for human health. In total, 5 species and 8 genera of fungi were identified in the collected samples, whereby there was significant growth only during the first 4 to 6 months of storage.

A fluorinated poly-acrylate emulsion with various fluorine contents was prepared by a seeded semi-continuous emulsion polymerization method and applied to filter paper for oil-water separation applications. The effects of surface wetting behavior on the oil-water separation efficiency of the prepared filter paper were studied. The results show that the prepared highly hydrophobic and superoleophilic filter paper presented 94.45 wt% water separation efficiency and strong mechanical strength. In addition, the oil-water separation stability and durability of the filter paper were also tested and shown to be suitable for use in real oil-water separation applications. These properties indicate that the filter paper has great potential applications in the oil-water separation industry.

The effect of time-dependent moisture absorption on the surface roughness in natural fiber/polypropylene composites after a hot-press molding was studied. The results showed that the moisture absorption in both bagasse and oil palm natural fiber composites correlated closely with time-dependent surface roughness in the composites. The surface roughness in all natural fiber composites increased with an increase of moisture absorption up to 50 d. The fibers absorbed moisture and swelled due to hydroxyl groups of celluloses in the natural fibers, which caused an increase in surface roughness. Time-dependent tests found that the surface roughness in long fiber composites was larger than that in short fiber composites due to inhomogeneous dispersion of long fibers in the vicinity of the surface of composites. The increase in surface roughness of oil palm composites was 55% that of the bagasse composites due to the lower temperature of thermal decomposition in oil palm fibers than in bagasse fibers. Thermal decomposition decreased the number of hydroxyl groups in fibers during heating and resulted in a decrease in moisture absorption in the palm fibers. Furthermore, the effect of the carbodiimide treatment on bagasse fibers was confirmed to reduce moisture absorption for both the fibers and the composites.

The in situ Fourier transform infrared (FTIR) spectroscopy technique was used as an online method for fundamental mechanistic studies of the pyrolysis of a lignin monomeric model compound. The formation of important reaction intermediates was revealed. Three major decomposition routes were shown: P1, dehydration at approximately 270 °C; P2.1, demethylation at approximately 350 °C; and P2.2, H-abstraction at approximately 430 °C. A free reaction of the pyrolysis of the lignin model compound was suggested based on the results. The comparative results showed that the methyl group was the initiator of many secondary reactions.

Columbian coffee trees are subject to frequent replacement plantings due to disease and local climate changes, which makes them an ideal source of wood fibers for wood plastic composites (WPC). Composites of polypropylene (PP) consisting of 25% and 40% by weight of coffee wood flour (CF) and 0% or 5% by weight of maleated PP (MAPP) were produced by twin screw compounding and injection molding. Composites containing MAPP had significantly improved tensile and flexural properties compared to neat PP or composites without MAPP. Excellent mechanical properties were obtained with CF relative to conventional wood fillers. Izod impact resistances of CF composites were significantly lower than neat PP although WPC containing MAPP were superior to WPC without MAPP. Bio-based fiber composites made by mixing CF in equal portions with other fiber sources were evaluated to determine the compatibility of using CF with other sources of filler materials. Soaking of tensile bars of the various CF blends in distilled water for 35 days may alter their mechanical properties and result in weight gain. Differential scanning calorimetry and thermogravimetric analysis were conducted on the neat PP and bio-composites to evaluate their thermal properties as they relate to potential degradation during conventional thermoplastic resin processing.

The goal of this study was to develop and test an appropriate method for the evaluation of surface quality and to identify and quantify the quality of a surface modified by 3D molding. New software was developed to evaluate the surface quality based on the identification of macroscopic defects such as cracks within a scanned area. The influence of specific factors that affect the development of cracks during the uneven pressing process was assessed. Based on the measured and evaluated results, a process combination of factors was designed which yielded an embossed surface that was formed with the lowest proportion of cracks and with sufficient shape stability. In this work, 432 groups of test pieces were monitored, with each piece exposed to different combination of factors. Based on the measured and evaluated results, we found a combination that provided the lowest crack ratio. This innovative method will contribute to the knowledge of embossed surface quality and to the improvement of the uneven pressing process for wood surfaces.

, industrial alkaline lignin/poly (vinyl alcohol) (PVOH) cross-linked films, industrial alkaline lignin/poly (vinyl alcohol) blend films, and neat poly (vinyl alcohol) films were prepared by casting. The films were investigated by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry analysis (TGA), and dynamic mechanical analysis (DMA). The water contact angles for the three kinds of films were studied as well. The crosslinking reaction between alkaline lignin and PVOH was strong, which was attributed to the high hydrolysis degree of PVOH and the high reactivity of formaldehyde. Compared with the neat PVOH film, the crystallinity of the cross-linked film decreased slightly; the thermal stability of the cross-linked film was higher; DMA analysis showed that the Tg and the tanδ magnitude of the alkaline lignin/PVOH reaction film both decreased slightly. Lignin and the cross-linking reaction both improved the water resistance of films. Therefore, this research has provided a detailed analysis of the characterization of the films while exploring the potential of direct usage of industrial alkaline lignin in polymer materials.

An effective strategy for sugar production from corn stover was established through a combination of green liquor pretreatment (8% total titratable alkali charge, 40% sulfidity, 140 °C, and 1 h) and enzymatic hydrolysis with a specialized enzyme cocktail. Green liquor pretreatment was demonstrated as an effective first step for sugar production due to the selective removal of lignin (39.70%), high carbohydrate recovery yield (81.53%), and obvious enhancement of enzymatic hydrolysis after pretreatment. When a specialized enzyme cocktail (cellulase, β-glucosidase, and xylanase at a ratio of 1:1.88:6.61, supplemented with 0.05 g of PEG 6000 per g of glucan) was applied, near-theoretical hydrolysis yield was achieved (glucan hydrolysis yield of 93.53% and xylan hydrolysis yield of 86.00%). A total fermentable sugar production of 50.14 g was obtained per 100 g of dry corn stover, including 36.08 g of glucose and 14.06 g of xylose.

Paper sheets were dipped in maleic anhydride-acylated chitosan (MAAC) to enhance their wet strength and antibacterial performance. The wet strength of paper sheets treated with MAAC or chitosan solutions and cured at 90 and 170 °C was investigated. Escherichia coli was used to evaluate the antibacterial performance of the treated paper sheets. The antibacterial performance was determined by measuring the absorbance at 610 nm based on the turbidity of the bacterial suspension on the surface of the treated paper sheets. The MAAC performed better than chitosan in improving wet strength, especially in the case of permanent wet strength. Paper sheets treated with MAAC under certain conditions resulted in 23 to 33% improvements in the permanent wet strength. As a result of the surface treatment, a reduction of at least 80% in E. coli growth was observed. The MAAC was more efficient in inhibiting the growth of E. coli than chitosan.

A simple, rapid, accurate, and practical headspace gas chromatographic method is proposed for the determination of hydrogen peroxide residues in bleaching effluent. of hydrogen peroxide with ceric sulfate, under acidic conditions, where hydrogen peroxide is converted to oxygen, which is then measured using headspace gas chromatography (HS-GC) coupled with a thermal conductivity detector (TCD). The results show that a complete conversion of hydrogen peroxide to oxygen can be achieved within 3 min at a temperature of 70 °C and a H2SO4 concentration of 0.2 M. Under optimized conditions, the method has an excellent measurement precision (relative standard deviation = 0.78%) and good recovery (100.2 ± 2.6%). does not require the use of organic reagents.