Volume 15 Issue 3

Aligned hydrogels have received increasing attention in tissue engineering and electrochemical fields due to their favorable structure. In this work, xanthan gum-based hydrogels (XGH) with aligned pores were prepared via photoinitiated free radical irradiation that used sodium acetate crystals as template. The microstructure, compressive strength, porosity, and absorption capacity of the hydrogel were studied and compared with the non-aligned hydrogels. Scanning electron microscope analysis confirmed the aligned porous structure of the hydrogel. The maximum compressive strength for the aligned hydrogel prepared with 12% acrylamide and 1.5% xanthan gum reached 0.439 MPa at a strain of 95%. Furthermore, aligned XGH exhibited better flexibility than non-aligned hydrogels, as indicated by the Young’s compressive modulus. The porosity of the aligned hydrogels ranged from 94.9% to 88.8% as the acrylamide concentration increased from 12% to 20%. Simulated body fluid absorption showed that hydrogels with aligned pores could attain absorption equilibrium within 5 min, and the maximum absorption capacity reached 33.6 g/g for the sample made with 0.5% xanthan gum and 12% acrylamide. In addition, exhibited preferable biocompatibility, as demonstrated by the cytotoxicity test.

Plant-derived biopolymers are renewable and readily available, thus making viable alternatives to synthetic polymers. The present study examined properties of biopolymers from cover crops such as rye, oat, clover, vetch, and barley, which were grown organically in a greenhouse. The yields of cellulose, hemicellulose, and lignin of the cover crops were calculated based on the dry weight. Structural variations and thermal properties of the isolated cellulose were characterized and compared with commercial cellulose using Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and Thermogravimetric analysis (TGA). The average yield percentages of cellulose, hemicellulose, and lignin were 19 to 27%, 9 to 25%, and 1.42 to 4.86%, respectively. The FTIR and Raman spectral analysis indicated that the isolated cellulose had similar peaks and patterns to commercial cellulose, and confirmed the removal of non-cellulosic constituents. The onset decomposition temperature occurred at 270 °C in all samples. Interestingly, the maximum degradation temperature beyond 370 °C in cellulose was isolated from black oat, which was higher than commercial cellulose (350 °C). The findings of this research suggest that cellulose isolated from cover crops may be a benefit to the polymer industry in the development of bio-based materials such as biofuels, bio-composites, and biomedical devices.

The objective of this research was to quantitate the amount of wood loss that occurs during the processing of freshly harvested fir roundwood into sawlogs. The influence of the felling damages and various growth defects, e.g., curvature, taper, and forked growth, were taken into consideration. The causes of wood loss and wood volume reduction during the three primary operations of this processing chain, under the considered limited conditions, were established. The greatest wood volume reduction recorded was an 11% decrease, which was caused by the crosscutting of the stems into shorter logs. Additional wood volume reductions were due to the selection (grading) of the sawable logs and to debarking (7% and 6%, respectively). Some recommendations, in terms of industrial applicability, i.e., methods to reduce the amount of wood loss, were also formulated.

Bio-oil can serve as an alternative fuel source or resource to extract high value-added chemicals. This paper focuses on the effect of six types of biomass (rape straw, corn straw, walnut shell, chestnut shell, camphor wood, and pine wood) and ZnCl2 catalyst on the bio-oil yield and chemicals in the bio-oil, including aldehydes, ketones, and four high-value chemicals (1-hydroxy-2-butanone, propionaldehyde, 5-HMF, 2(5H)-furanon). The results showed that the yields of bio-oil decreased when the ZnCl2 was the catalyst. The ZnCl2 promoted the production of aldehydes and ketones. The higher contents of aldehydes and ketones were obtained from camphor and pine wood, at 58.9 wt% and 42.0 wt%, respectively. The ZnCl2 catalyst exhibited an active influence on the production of 1-hydroxy-2-butanone, propionaldehyde, 5-HMF, and 2(5H)-furanon. Compared with the non-catalytic pyrolysis, the content of 1-hydroxy-2-butanone and 2(5H)-furanone in bio-oil increased by 936% and 612%, respectively. The contents of propionaldehyde and 5-HMF in catalytic bio-oil were the highest from rape straw and increased by 193% and 86%, respectively.

Polylactic acid (PLA) biocomposites were prepared by melt blending in an internal mixer with various types of rubber. The rubber was 90/10 wt% and was mixed before the addition of kenaf fiber (0 to 20 phr). Natural rubber (NR), nitrile butadiene rubber (NBR), and styrene butadiene rubber (SBR) were used. The effects of different types of rubber and kenaf loading were investigated based on processing torque, water absorption, mechanical properties, and fractured surface morphology. A similar trend in processing torque was observed throughout the composition of biocomposites. The stabilization torque was highest for the biocomposite with NR, followed by SBR and NBR. Water absorption increased as the kenaf loading increased. The polarity of NBR and SBR contributed to higher water absorption in the biocomposites compared to the NR. The strain-induced crystallization phenomenon and higher green strength of NR contributed to the highest tensile strength, elongation at break, and impact strength of the biocomposite compared to the NBR and SBR toughened PLA/kenaf biocomposite. More plastic deformation and less fiber pullout were observed in the fractured surface morphology. However, by increasing the kenaf loading, the mechanical properties decreased for all biocomposites, which was due to poor interfacial adhesion and agglomeration.

Three healthy Citrus sinensis (orange) trees in Babol, Iran, were randomly selected and cut. Two discs of 5 cm thickness were prepared along the tree (breast height and crown). In the transverse direction, the test specimens were cut 2 × 2 cm to 3 cm from the pith to the bark sequentially and examined. The biometric and physical properties were measured, and microscopic sections of wood near the bark were studied using light microscopy according to the International Association of Wood Anatomists’ (IAWA) List. Anatomical examination of the C. sinensis wood showed that the species was a diffuse porous hardwood, with indistinct growth rings, simple perforation plates, alternate intervessel pits, and banded parenchyma. The basic density and oven-dry density increased from the pith towards the tree bark and from the bottom of the tree towards the crown. There was a significant difference in both the transverse and longitudinal directions of the C. sinensis tree in terms of fiber length, fiber lumen diameter, fiber diameter, and cell wall thickness. The mean fiber length, fiber diameter, fiber lumen diameter, and cell wall thickness were 0.76 mm, 23.64 µm, 9.23 µm, and 14.41 µm, respectively.

A new type of sustainable material, i.e., a sisal fiber/poly-ether sulfone composite (SFPC), which is energy-efficient, environmentally friendly, and has a low cost, was developed for laser sintering additive manufacturing. This study was performed to explore the effects of the processing parameters on the SFPC composite parts produced via selective laser sintering (SLS). The effects of the laser sintering processing parameters, i.e., the preheating temperature, laser power, and scan speed, were studied. Bending and tensile testing of the SFPC specimens was successfully performed via SLS. The effect of the processing parameters on the SLS in terms of the mechanical strength of the laser-sintered parts was investigated. The results determined that the processing parameters had a significant effect on the mechanical strength of the sintered SFPC parts. When the preheating temperature and laser power were increased in the processing SLS system, the mechanical strength of the sintered SFPC parts was significantly increased. However, the scanning speed had an inverse proportional relationship to the mechanical strength of the SFPC SLS parts.

Glued laminated timber (glulam) is a wood-based product with frequent use in timber construction. Maritime pine (Pinus pinaster Ait.) is a species suitable for glulam production and is available with abundance in Portuguese forests. This study assessed the influence of the phase in which the preservative treatment is applied in the surface bonding performance. Several elements were produced considering different treatment scenarios: timber without treatment, timber treated before gluing, and timber treated after gluing. The bonding quality was tested by both shear strength and delamination tests, following the indications given in EN 14080 (2013). Glulam elements treated after gluing (TAG) presented less delamination when compared with the ones treated before gluing (TBG). However, TBG elements presented higher shear strength values than TAG elements. Despite the recorded differences, all the considered sets performed adequately both for delamination and shear strength tests.

A widely applicable electromagnetic interference (EMI) shielding and decorative thin veneer containing copper was prepared with simple electroless technology. Copper was used as the structural and EMI reflection component to reinforce the mechanical strength and EMI shielding effectiveness. Both the texture and structural properties of copper deposited on poplar wood were characterized. The X-ray diffraction patterns indicated that the copper deposited on poplar wood had a crystallite size between 7.9 nm and 15.9 nm, and the copper crystallites grew rapidly as the number of electroless runs increased, which was consistent with the resistivity and microscopy analyses. The mechanical and EMI shielding effectiveness results showed that after two electroless runs, the wood veneer surface was completely covered, which improved the EMI shielding effectiveness and mechanical properties of wood veneer. The material could be bent 360° without being damaged and had a good decorative effect.

The effects of lignocellulosic filler type and filler loading levels were investigated relative to selected properties of thermoplastic polyurethane (TPU)-based composites. Teak wood (TK), rice husks (RH), and microcrystalline cellulose (MCC) were used as lignocellulosic fillers at 15 wt% and 30 wt% filler loading levels. Test specimens were manufactured using both extrusion and injection molding, except for abrasion resistance samples that were manufactured using a compression molding process. Density, tensile, flexural, and impact properties, and hardness and abrasion resistance values, of the specimens were determined. The composites’ morphology was studied using scanning electron microscopy analysis; results showed all filler types and filler loading levels were affected by the TPU’s density and mechanical properties. The TPU composites were successfully produced using TK, RH, and MCC as lignocellulosic fillers. Regardless of filler type, addition of 15% filler to TPU yielded excellent mechanical properties. With 30% MCC filler, composite properties increased due to their higher surface area, while properties of TK- and RH-containing specimens were, at 30%, reduced. There was a proportional correlation between hardness and modulus, with both increasing with a rising filler loading level. Abrasion resistance of TPU decreased with the presence of filler. Regardless of filler type, abrasion resistance continued to drop at higher filler loading levels. Scanning electron micrographs showed better MCC distribution in the TPU matrix.