Volume 7 Issue 4

Two of the drawbacks of using natural-based composites in industrial applications are thermal instability and water uptake capacity. In this work, mechanical wood pulp was used to reinforce polypropylene at a level of 20 to 50 wt. %. Composites were mixed by means of a Brabender internal mixer for both non-coupled and coupled formulations. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the thermal properties of the composites. The water uptake behavior was evaluated by immersion of the composites in water until an equilibrium state was reached. Results of water absorption tests revealed that the amount of water absorption was clearly dependent upon the fiber content. The coupled composites showed lower water absorption compared to the uncoupled composites. The incorporation of mechanical wood pulp into the polypropylene matrix produced a clear nucleating effect by increasing the crystallinity degree of the polymer and also increasing the temperature of polymer degradation. The maximum degradation temperature for stone ground wood pulp–reinforced composites was in the range of 330 to 345 ºC.

Chitosan (CS)/cellulose (BC) blend films were successfully prepared using ZnCl2·3H2O as a solvent. Homogeneous structures without obvious phase separation between CS and BC for all blend films were observed by scanning electron microscope (SEM) analysis. The tensile strengths of CS/BC blend films decreased with the increase of chitosan content. The results of X-ray diffraction (XRD) analysis indicated that the crystal structures of BC and CS were disrupted during the processes of dissolving and regeneration. Also, the reformation of hydrogen bonds between CS and BC during dissolution and regeneration processes resulted in the shift of diffraction peaks. Fourier transforms infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) analysis results confirmed this observation. Moreover, obvious antimicrobial capability of CS/BC blend films against E. coli has been observed, indicating that antibacterial activity of chitosan has not been significantly inactivated while using ZnCl2·3H2O as a solvent. Therefore, ZnCl2·3H2O can be regarded as a promising solvent to prepare degradable films with antibacterial properties.

Grasses are abundant in many climatic regions of the world and have been regarded as weeds by many. This work investigated the use of Pennisetum purpureum (Napier grass) in the production of bioethanol. Two pretreated grasses were compared as the initial substance in the hydrolysis process followed by bacteria fermentation. For the purpose of breaking down lignin, alkali pretreatment, where grass was soaked in 7% NaOH, was used. For biological pretreatment, grass was incubated for 3 weeks with the white-rot fungus, Phanerochaete chrysosporium. Both types of pretreated materials were subjected to Trichoderma reesei ATCC 26921 enzyme hydrolysis. Glucose content from alkali-pretreated samples was 1.6-fold higher than fungus-pretreated samples. Hydrolysates from the pretreatments were fermented using the ethanol insensitive strain Escherichia coli K011. After 24 hours of fermentation, the ethanol yield from alkali-pretreated material was 1.5 times higher than the biological-pretreated material. It can be concluded that NaOH-pretreated enzyme hydrolysate had a better ethanol yield compared to biological-pretreated enzyme hydrolysate, but biological-pretreated enzyme hydrolysate had better ethanol conversion efficiency, which was 18.5 g/g. These results indicated that wild grass is capable of becoming an important biomass for small local bioethanol production.

Coextruded wood-plastic composites (WPCs) with glass-fiber (GF) filled shells were manufactured, and their thermal expansion behavior was studied. A three-dimensional finite element model (FEM) considering differential properties of both shell and core layers was developed to predict the linear coefficient of thermal expansion (LCTE) of the material. It was shown that the LCTE values varied with composite structure and composition (i.e., core-shell thicknesses and materials). The use of GF-filled shells helped lower overall composite LCTE values. The imbalance of shell and core LCTE, and their moduli led to complex stress fields within a given composite system. The FEM predicted a trend of LCTE change with varying composite structures, which was in good agreement with the experimental data. This study provides for the first time a finite element modeling technique to optimize raw material composition and composite structure for optimizing thermal expansion behavior of co-extruded WPCs.

Common metrics for evaluating the efficiency of oxygen delignification include the kappa number and Klason lignin content. As a change in xylan content often leads to a change in HexA content, the kappa number must be corrected for the HexA contribution before evaluating the degree of oxygen delignification when trying to understand the process in detail. Questions could also be raised about the accuracy of the Klason lignin method for oxygen-delignified hardwood kraft pulps, since the amount of residual lignin is small in such pulp. This study investigates the influence of xylan content on oxygen delignification efficiency in Eucalyptus urograndis kraft pulps. Xylan content was varied using two methods: treatment with xylanase and with acid prehydrolysis for various times before kraft cooking. The degree of oxygen delignification, expressed as the HexA-corrected kappa number, indicated no significant trend with xylan removal, and no significant trend was evident when expressed as Klason lignin content.

This paper puts forward a novel non-ionic augmentation system, namely, gelation of native starch in the presence of borax and papermaking fibers. Native starch was blended with high concentration pulp and auxiliary agents. After pasting, the starch gel adhered onto fiber surfaces. However, an excess dosage of agents led to a rigid structure and poor gel strength. Starch became gelatinized and then cross-linked by borax and cured as an adhesive layer through the process of pressing and drying under a high temperature. This provided close and uniform contact between starch and fibers. As a result, the strength of the paper was increased after forming.

Activated carbon fibers were prepared from liquefied wood through stream activation. The effects of activation temperature and time on the microstructure and surface functional groups of the liquefied wood activated carbon fibers (LWACFs) were studied using analysis of burning behavior, X-ray diffraction, nitrogen adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and SEM. The results showed that the burn-off value of the LWACFs increased gradually with the increase in temperature or time. All the LWACFs were far from being structurally graphitized, and in general, as temperature or time increased, the degree of graphitization and thickness of crystal structure increased. In addition, the LWACFs possessed rich micropores, and their specific surface area, pore volume, micropore size, and mesopore quantity were directly related to the activation temperature or time. The maximum specific surface area was found to be 2641 m2/g. The fractal dimension values of all samples were close to 3, indicating that their surfaces were very rough. Furthermore, with an increase in temperature or time, the elemental content of carbon increased, while that of oxygen decreased. Meanwhile, as the temperature or time increased, the relative content of graphitic carbon decreased, whereas that of carbon bonded to oxygen-containing functions increased. The surface of samples prepared at higher temperature or with longer time formed a considerable amount of holes.

The effect of the degree of deacetylation of chitosan on the chemical structure, thermal properties, and compatibility of chitosan/polyamide66 (CS/PA66) blends were investigated. Blends of CS with PA66 were prepared via the solution casting technique by using 85% formic acid. Structural interaction between PA66, CS, and CS/PA66 blends were analyzed by infrared spectroscopy. FT-IR spectra showed displacement of the carbonyl band of the amide group of chitosan toward smaller wave numbers, indicating possible existence of hydrogen bonding between the two macromolecules. Thermal and morphological behavior of films containing chitosan with degree of deacetylation (DD) ranging from 52.9% to 85% in the polymer blends were investigated by thermogravimetric analysis and scanning electron microscopy. Thermal analysis showed that the CS/PA66 blends became more thermally stable than pure chitosan. The morphological behavior observed by scanning electron microscopy indicated phase segregation in all types of blending. Acetyl content in chitosan was found to influence the degree of compatibility. Decreasing the acetyl group or increasing the DD of chitosan increases the compatibility of the CS/PA66 blends.

As wood’s density increases, strength properties tend to increase due to a decrease in cavity volume. This study aimed to determine the effect of temperature levels in the densification process with an open-system thermomechanical method on the density, bending, modulus of elasticity in bending, compression, shear strength, and Brinell hardness in radial/tangential directions of Scots pine. The densification process significantly increased the strength properties of Scots pine. This increase stemmed from the decrease in the rate of cavities with the densification process, which also resulted in an increase in cell wall elements that have load-bearing properties per unit volume. An increase in densification temperature decreased strength properties. The decrease in the strength values can be explained by increasing chemical degradation with a rise in the temperature level. The most suitable temperature level was 120 ºC for a higher bending, shear, and compression strength, and it was 140 ºC for a higher radial and tangential hardness in the densification of Scots pine. Increases of 42% in the bending strength, 20% in the shear strength, 47% in the compression strength, 242% in the radial hardness, and 268% in the tangential hardness were obtained after densification.

The emotional and psychological activities associated with the visual perception of macroscopic and microscopic structure patterns of wood were investigated. The macroscopic and microscopic structure patterns of 18 different timber tree species of northeast China were selected as the research objects, and these were divided into eight categories for event-related potential analysis. The 30 effective subjects’ tasks were to watch the wood structure stimuli patterns and evaluate them on a 7-point bipolar scale. The results showed that the emotional valence of the wood structure stimuli patterns of the eight categories evoked P2 and late positive potential (LPP) composition in a specific area of the brain. P2 refers to an early perception analysis processing for visual perception of the wood stimuli patterns, while LPP refers to late processing and reflects evaluations when people face different wood stimuli patterns. The results also indicated that people prefer to connect the understanding of macroscopic and microscopic patterns of wood with their own mood. Evaluation processing for macroscopic and microscopic structure patterns of wood were based on visual perception analyses, which were judged by personal feelings and decisions. People made active emotional assessments of the macroscopic and microscopic structure patterns of wood.