Volume 10 Issue 1

Hydrogels have been widely studied as tissue engineering scaffolds due to their swelling capabilities in water and other physical properties. In this study, phosphatized PVAs of varying degrees were prepared by esterification of phosphoric acid, and a freeze-thaw technique was introduced to fabricate hydrogels from hemicelluloses, poly(vinyl alcohol phosphate) (P-PVA), and chitin nanowhiskers. The obtained hydrogels were characterized by Fourier transform infrared (FT-IR) spectrometry, scanning electron microscopy (SEM), X-ray diffraction (XRD), and CP/MAS 13C nuclear magnetic resonance; their swelling properties and compressive strength were also determined. The repeated freeze-thaw cycles induced physically crosslinked chain packing among the three polymers by hydrogen bonds. The results showed that the hydrogels possessed higher swelling ratio and mechanical strength when the PVA was phosphatized by phosphoric acid and urea and more hydroxyl groups were introduced into the polymer matrices. This suggested that hydrogels with good mechanical properties were prepared successfully by the freeze-thaw technique.

Combining two kinds of fibers is a potential way to improve the essential properties of natural fiber-reinforced hybrid polymer composites. Biocomposites produced from natural resources are experiencing an increase in interest due to their high demand in the market for manufacturing, in addition to environmental and sustainability issues. In this study, natural fiber-reinforced hybrid polymer nanocomposites were prepared from coir fiber, wood fiber, polypropylene, and montmorillonite nanoclay using a hot press technique. The effects of fiber mixing and montmorillonite on their physico-mechanical and biodegradable properties were subsequently investigated. Before being used, both the wood and the coir fibers were alkali-treated to reduce their hydrophilicity. The mechanical properties of the fabricated composites were measured using a universal tensile testing machine and found to be enhanced after fiber mixing and nanoclay incorporation. Fourier transform infrared spectra indicated that the characteristic peaks of the composites shifted after fiber mixing. A new peak around 470 cm-1 was observed in the case of the nanocomposites, which confirmed the interaction between the fiber, polymer, and montmorillonite (MMT). Scanning electron microscopic analysis revealed that MMT strongly improved the adhesion and compatibility between the fiber and polymer matrix. The combining of fibers improved the biodegradability and water absorption properties, while MMT addition had the reverse effect on the same properties of the composites.

Lignin is an attractive, renewable raw material provided by all types of agricultural and silvicultural vegetation. The precipitation of lignin fractions through acidification of the black liquor was performed and the products characterized for the following parameters: C, H, N, and S elemental composition; zeta potential; electrophoretic mobility; heating value; molecular weight; content of non-conjugated, conjugated, and total phenolic hydroxyl groups; and total yield of oxidation products. Lignin was isolated from black liquor by adding sulphuric acid at four levels of concentration (5, 25, 50, and 72 wt%) and subsequently adjusting the pH to 5. A comparison study of the physico-chemical and surface properties was also performed. The acid concentration influenced the yield of precipitated lignin and had an effect on the properties of precipitated lignin and the content of non-conjugated, conjugated, and total amount of phenolic hydroxyl groups. However, the concentration of acid had no relevant effect on the heating value, molecular weight, polydispersity, total yield of oxidation products, or the elemental composition of isolated lignin.

The focus of this research was to study the utilization of residues from bamboo (Dendrocalamus giganteus) lamination in the manufacturing of panels for structural purposes. Bamboo particleboards were produced under three conditions: pure boards, reinforced with bamboo laminas, and with treated particles. Castor oil-based polyurethane was the resin binder, in view of using lower toxicity materials. The mechanical tests were performed according to Brazilian Standard (NBR) 14810-3 (2006) and European Standard (EN) 310 (2000). The results were superior to those recommended by these and other standards for internal adhesion resistance, modulus of rupture, and elasticity in static bending, as well as to the results of other studies. Starch treatment was an unnecessary stage. According to the conditions of this process, the studied panels showed a good potential for construction use. Moreover, the bamboo particleboards are an economically viable, environmentally friendly, and sustainable alternative for the use of waste generated during the processing of Dendrocalamus giganteus bamboo species, allied with castor oil-based polyurethane resin. The reinforced particleboard and its production process are being licensed as an Innovation Patent in Brazil, (BR 1020130133919-1-2013).

Xanthan gum (XG) is a polysaccharide produced by Xanthomonas campestris. The aim of the present study was to modify the xanthan by hydrolysis and grafting with acrylamide through microwave irradiation for different time intervals. Pure xanthan was partially hydrolyzed via enzymatic and chemical treatments followed by optional grafting. Proximate composition analysis, moisture content, and carbohydrate, protein, lipid, and fiber contents were determined. The morphological characteristics, structural composition, functional groups, and heat resistance of the crude, hydrolyzed, and grafted gum were evaluated using SEM, XRD, FTIR spectroscopy, and TGA. Morphological studies revealed that xanthan was broken down into smaller fragments as a result of hydrolysis and became somewhat smoother. Thermal analysis studies indicated a larger heat tolerance in the grafted xanthan relative to that of the native and hydrolyzed gums. Xanthan bound to a triamcinolone drug was evaluated in the context of controlled drug release. Controlled drug release correlated well with the exposure time to microwaves used to graft the gum.

Combustion characteristics and thermal dynamic characteristics of blends of inferior coal and core plywood under different oxygen-enriched atmospheres were investigated using thermogravimetric (TG) analysis. According to the results, with increasing oxygen concentration, TG and DTG curves tended to move to a lower temperature region. The comprehensive combustion characteristic index SM was first proposed in this work, suggesting that the enriched oxygen concentration can significantly improve the combustion conditions. Apparent activation energies were also put into the calculation and analysis, which showed that the apparent activation energy increases with an increasing oxygen concentration. The factor Fc was defined for the first time, and it was found that Fc can represent the temperature at which combustion can proceed under the same blend ratio condition.

This article is focused on the impact of different binder mixtures on the performances of paper surface and printability. The coating properties were studied with the chosen silica pigment, and the binder consisted of vinyl acetate copolymer and polyvinyl alcohol with different ratios, followed by the measurement of smoothness, whiteness, and surface strength. The inkjet image quality was assessed using water-based inks. The print density, dot gain, and line quality were analyzed. The results showed that the surface performance and printability were affected by the composition of the binder. With the decrease of vinyl acetate copolymer and the increase of polyvinyl alcohol, the surface smoothness and strength decreased, and the penetration and diffusion of the ink changed as well. When the binder mixture was used with proper ratio, a larger solid density, smaller dot gain, and higher definition can be achieved, which were better than using either one of them alone.

Sawing small diameter logs results in lower yield compared to sawing large diameter logs. This is due to geometry; fitting rectangular blocks inside an approximately cylindrical shape is more difficult for small than for large diameters. If small diameter logs were sawn in a way that follows the outer shape, yield would increase. The present study considers whether this can be done by sawing flitches into trapeze shapes. These can be glued together into rectangular products. Cross laminated timber (CLT) products are suitable for this. The study was based on 4,860 softwood logs that where scanned, and the scanning data was used for sawing simulation. The log top diameters ranged from 92 to 434 mm. The volume yield of CLT production using trapeze edging was compared to cant sawing of boards. The trapeze edging and CLT production process improved yield compared to cant sawing by 17.4 percent units, for logs of a top diameter smaller than 185 mm. For all logs, the yield decreased using the trapeze edging method. To conclude, a trapeze edging method shows promise in terms of increasing volume yield for small diameter logs, if boards can be properly taken care of in a CLT production process.

This study aimed to investigate the changes in the fiber characteristics, relative crystallinity, and impact toughness of heat-treated Eucalyptus urophylla × E. camaldulensis. Samples were treated in a superheated steam kiln at 160, 180, 200, and 220 °C for 3 h. The crystallinity, length-width ratio of fibers, and impact toughness of the heat-treated and untreated wood were determined. The cellulose crystalline regions experienced no obvious change. However, the length-width ratio and the relative crystallinity of the fibers increased as the temperature increased. Results indicated a clear inverse trend in the impact toughness and relative crystallinity. Finally, the results could provide a new method for non-destructive testing of wood.

In the present study, polypropylene, recycled natural rubber gloves, and oil palm ash composites (PP/rNRg/OPA) were prepared using an internal mixer. The effects that OPA loading had on the processability, tensile properties, morphology, and thermal stability of the PP/rNRg/OPA composites were investigated. The stabilization torque, tensile modulus, and thermal stability all increased; however, the elongation at break decreased as the OPA loading increased. The tensile strength increased to a maximum of 4 parts per hundred rubber (phr) OPA loading, and subsequently decreased. At 4 phr OPA, the filler was well-dispersed and had a good interaction with the matrix, whereas the agglomeration and detachment of OPA was observed at high loading rates of OPA in the PP/rNRg/OPA composite. Thermogravimetric analysis (TGA) indicated that the thermal stability of the composite increased as the OPA loading increased. Further evidence for the increased thermal stability can be found when analyzing the decomposition temperatures at different stages and maximum weight loss, where higher decomposition temperatures corresponded to composites with higher OPA loadings.