Volume 14 Issue 2

Fast-growing species are gradually being used more in the Brazilian timber market. Such species are more susceptible to deterioration and require conservative treatment to prolong their service life. This work analyzed the influence of the chromated copper arsenate oxide (CCA-A) treatment on the physical-mechanical properties of the tropical woods Simarouba amara (C20), Cedrelinga catenaeformis (C30), and Erisma uncinatum (C40), which were chosen to cover the three lower strength classes, as prescribed by Brazilian Standard Norm. The CCA-A was applied to the wood with the vacuum-pressure process, which could increase the amount of surface defects and weaken the wood properties. To investigate the influence of this process, complete characterization of the species with and without CCA-A was performed, and a Tukey’s multiple comparisons test (5% significance level) was applied. Also, scanning electron microscopy (SEM) images and energy dispersive spectra (EDS) were obtained to investigate the behavior of the preservative at the cellular level. Through the obtained results, it was concluded that the CCA did not affect the physical-mechanical properties of the studied species.

Fibre metal laminates (FML) were reinforced with flax and sugar palm fibres in different stacking sequences and exposed to freezing conditions. The effects on the mechanical properties were explored. Both the stacking sequence and freezing condition affected the mechanical properties. The FML with flax fibres showed the highest strength and modulus under tension and bending, while the FML with sugar palm fibres showed the lowest strength and modulus. The FML with flax fibres experienced a fibre bridging effect and showed promising behaviour for aircraft applications by sustaining nearly 40000 cycles of fatigue load. Decreases in the strength, modulus, and fatigue life occurred when the FML specimens were exposed to freezing conditions. Micrographs from the tensile fractured specimens indicated delamination, fibre splitting, fibre breakage, and fibre/matrix de-bonding as the failure pattern for the pristine and conditioned laminates.

Nanoscale material has attracted the interest of many researchers because of its special physicochemical and surface properties. In this study, a nanocomposite was prepared based on cellulose nanocrystals (CNCs) in situ forming ultra-fine size gold nanoparticles. To form the gold nanoparticles, chloroauric acid was reduced with an aqueous mixture of ethanol and CNC. The gold nanoparticles were less than 8 nm in size, with 80% of them less than 5 nm. Nanocellulose in the preparation system acted as a stabilizer. The size and dispersity of the ultra-fine gold nanoparticles (UAuNPs) were controlled by adjusting the pH. The resulting UAuNPs/CNCs composite exhibited excellent catalytic performance to eliminate solubilized NaNO2 mixed with NH4Cl at room temperature. The apparent rate constant of the reaction was 4.12 × 10-5 s-1. The catalytic effect of the generated UAuNPs on NO2- reduction has potential use in many fields, particularly in the food and environmental sectors.

Changes were evaluated in cell wall components, hygroscopicity, and thermodynamic properties of Pinus sylvestris L. wood that had been in contact with salt (NaCl) for 300 years in a former saltworks storehouse in Gerri de la Sal (Lérida, Spain), comparing it with recently felled wood (new wood) of the same species. The wood in contact with salt (salt-covered wood) had higher equilibrium moisture content values except in the first interval of the adsorption isotherm, probably because of mechanical blocking of polar sites by salt crystals. The high fibre saturation point values of this wood are caused by the salt dissolved in water above water activity of about 0.75. More energy is invested in the desorption process, and the values are higher in the salt-covered wood.

Refining is a primary unit operation that has a large impact on the quality of paper products and cost of production. The refining process of cellulose fibers is the most energy-intensive step in the preparation of paper pulp. High energy consumption during the refining process has motivated researchers to improve the economics of the process without decreasing the strength of the paper produced. This objective can be realized through easily refined pulps that are produced from alternative vegetal fibrous raw materials. This work compares the energy consumption of refining soft, hardwood, and fast-growing fibrous materials to 30 °SR. The goal was to reduce energy consumption while maintaining the strength properties of the paper received. For this purpose, cellulose pulps from fast growing plants including poplar, larch, and grasses were used.

Ecofriendly biodegradable composites were developed to mitigate the impact they have on the environment. Composites made from completely biodegradable materials were prepared using kenaf fibres and polyhydroxybutyrate (PHB). The composites were mixed using a twin screw extruder and injection moulded into dumbbell-shaped specimens. The composites were subjected to thermal analysis via differential scanning calorimetry (DSC) and mechanical testing (tensile and flexural tests). The addition of alkali-treated kenaf fibre reduced the crystallinity of PHB (up to 6% reduction), making it more ductile. The rheological behaviour of PHB was modified with the addition of kenaf fibres. Additionally, the flexural modulus was improved by up to 11% with the addition of kenaf fibres, for both the treated and untreated kenaf fibres. However, it was also observed that to improve fibre matrix adhesion, an alkali treatment alone is insufficient, as shown by the 16% reduction of tensile strength in composites with 20% fibre loading.

Bamboo-willow is a type of fast-growing wood with a high hemicellulose content. In the present study, the effects of phosphoric acid addition on the main components of bamboo-willow and pre-hydrolysis liquor (PHL) were explored, and subsequently the pre-hydrolyzed bamboo-willow chips were cooked, O–H–P bleached, and acid post-treated to produce dissolving pulp. The results showed that adding phosphoric acid to the pre-hydrolysis stage effectively removed hemicellulose and increased the cellulose content of the pre-hydrolyzed bamboo-willow. The major component of the hemicelluloses was xylan/xylose, which represented approximately 62% to 78% of the total sugars in the PHL. Glucose was the most abundant sugar that was produced, apart from xylose, and represented approximately 12% to 25% of the total sugars in the PHL. Additionally, 73% to 83% of the total sugars in the PHL were in an oligomeric form. The obtained bamboo-willow dissolving pulp could be used to produce viscose rayon with a 92.1% α-cellulose content, 4.77% hemicellulose content, and 675 degree of polymerization.

The stability of cellulase in the presence of ionic liquids (ILs) is pivotal for the in situ saccharification of cellulose. This study investigated the effects of various carbon sources on the cellulase production of Paenibacillus sp. LLZ1. The results showed that the activities of both the total cellulase and endoglucanase induced by microcrystalline cellulose were higher than those induced by other examined carbon sources. Simultaneously, a zymography analysis revealed the presence of seven protein bands (carboxymethylcelluloses 3, 4 and 6 through 10) with endoglucanase activity when MCC was used as the carbon source for culturing Paenibacillus sp. LLZ1. The endoglucanase induced by MCC showed stability in a 25% solids 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP) solution. Furthermore, the addition of metal ions and surfactants increased the endoglucanase activity in the [Emim]DEP solution, where 0.5 mM of Fe2+ and 0.1% of polysorbate (PSM 60) led to 11% and 29% increases in filter paper activity, respectively. Finally, three types of biomass (MCC, bagasse cellulose, and bagasse) were used as raw materials for in situ enzymatic hydrolysis when involved 5% [Emim]DEP and 0.1% polyoxyethylene (60) sorbitan monostearate (PSM 60). Fourier-transform infrared spectroscopy and specific surface area measurements were used to explain the effects of PSM 60 on the hydrolysis efficiency of these three biomasses.

The extraction process was optimized and compositional analysis was carried out for bioflocculant produced by Klebsiella M1. Single factor and response surface tests were adopted to optimize extraction of the bioflocculant. Physical and chemical tests were performed to qualitatively and quantitatively determine the chemical components of the bioflocculant. The molecular structure was analyzed by ultraviolet spectroscopy, Fourier transform infrared spectroscopy, gas chromatography, nuclear magnetic resonance spectroscopy, gel chromatography, and scanning electron microscopy. The optimum extraction conditions for the flocculant produced from Klebsiella M1 bacteria were as follows: anhydrous ethanol as the extractant, a material to liquid ratio of 1.54:1, pH of 9.06, and an extraction time of 12 h. The flocculant yield was up to 3.91 g/L. The bioflocculant was composed mainly of polysaccharides (65.9%) and proteins (19.7%). The polysaccharide molecular weight was 4.78 × 106 D, and it was comprised of L-rhamnose, L-arabinose, L-fucose, D-xylose, D-mannose, D-glucose, and D-galactose at the ratio 0.29:0.36:1:0.31:0.47:0.57:1.01. The polysaccharide contained hydroxyl and oxygen-containing functional groups (δ = 3.5 to 4.5 ppm) and aromatic groups (δ = 7 ppm). Thus, the bioflocculant produced by M1 bacteria was a polysaccharide type and anhydrous ethanol was a suitable extractant.

Rubber tree and oil palm are industrial crops cultivated in the same climate and environment. These plants are used to prepare nanocomposites of natural rubber and cellulose from empty fruit bunches, an abundant residue in the palm oil industry. For this study, the cellulose particles were extracted from the bunches and subjected to enzymatic hydrolysis or microfibrillation to produce nanostructured particles. The nanoparticles were blended with natural rubber latex in an aqueous medium, and the mixture was dried. The properties of the nanocomposites were compared to those of pure natural rubber and unprocessed cellulose composites. The mechanical properties of the natural rubber can be modified by the cellulose content and morphology. As a consequence, it is possible to modulate the material properties by changing only the filler morphology. The use of microfibrillated cellulose had stronger reinforcement effects. The thermal properties of natural rubber were not affected by the addition of cellulose.