Volume 7 Issue 4

Tannin-boron wood preservatives were investigated for their resistance against outdoor agents. This work focused on the analysis of the causes that affect the durability of the tannin-hexamine-treated samples. In particular, dimensional stability, resistance to leaching, and resistance to biological agents were investigated. The combined effect of deterioration agents was evaluated by subjecting the treated samples to simulated and natural weathering tests. The study of the appearance and of the color components (L*, a*, and b*) according to CIELAB space of the exposed samples was monitored to assess the efficacy of the tannin-boron formulations for outdoor applications. Significant resistance against the action of water (EN 84, ENV 1250-2) and insects (EN 47) has been demonstrated in specific tests. Conversely, the continuous stress due to artificial and natural weathering deteriorates the color and the visible features of the treated specimens. The combined effect of moisture modifications, solar exposition, and leaching cycles damages the structure of the tannin-based polymeric network and subsequently it negatively affects its preservation properties.

Pretreatment of sawdust using a combination of sodium hydroxide (NaOH) and monochloroacetic acid (MCA) was investigated for the formation of reducing sugars. Optimum conditions for the pretreatment process were determined by the amount of reducing sugars formed during the enzymatic hydrolysis of the pretreated substrate. It was found that mercerization by NaOH played an important role in increasing the degree of substitution (DS) and that the maximum solubility was achieved during the etherification by MCA. A maximum amount of 34.2% lignin was removed in the process. As the DS of the substrate was increased, the efficiency of the hydrolysis process increased, leading to the higher yield of reducing sugars. The optimum operating conditions for the pretreatment process were determined to be 75 ºC at 90 rpm for 4 hours (2 hours for mercerization plus 2 hours for etherification). Under these operating conditions, with 1% (w/v) NaOH and 2% (w/w) MCA loading, a maximum DS of 0.2 and a solubility of 10.3% was attained. At 75 ºC and after 48 hours of the hydrolysis process, cellulases from Aspergillus niger resulted in the production of 2.88 g/L of glucose with a yield of 62.72% reducing sugars. X-ray diffraction (XRD) revealed reduced crystallinity of the sawdust and Scanning Electron Microscopy (SEM) showed distortion of the structure after pretreatment.

In this work, the physical and mechanical properties of bleached Eucalyptus pulp reinforced with nanofibrillated cellulose (NFC) are compared with those of traditional beaten pulp used in the making of writing/printing and offset printing papers. For this purpose, three different types of hardwood slurries were prepared: beaten pulps, unbeaten pulps reinforced with NFC, and slightly beaten pulps also reinforced with NFC. Physical and mechanical tests were performed on handsheets from these different slurries. The results showed that adding NFC to unbeaten pulps results in physical and mechanical properties similar to those in pulps used for printing/writing papers. Nevertheless, the best results were obtained in slurries previously beaten at slight conditions and subsequently reinforced with NFC. These results demonstrate that the addition of NFC allows a reduction in beating intensity without decreasing the desired mechanical properties for this specific purpose.

High-Density Polyethylene (HDPE)-based composites with alkaline copper quaternary (ACQ)- and micronized copper quaternary (MCQ)-treated wood fibers were manufactured through injection molding. The mechanical properties, water absorption, and biological resistance properties of the fabricated composites with different coupling treatments were investigated. Composites with ACQ- and MCQ-treated wood had mechanical properties comparable with those made of untreated wood. The different coupling agents worked well for the treated wood materials. Similar water absorption behaviors were observed for the HDPE composites containing treated wood and those containing untreated wood. The results of the termite test showed that the composites containing untreated wood had slightly more weight loss. The decay test revealed that the composites containing treated wood had less decay fungal growth on the surfaces, compared with samples from untreated wood, indicating enhanced decay resistance for the composites from the treated material. The stable mechanical properties and improved biological performances of the composites containing treated wood demonstrated the feasibility of making wood-plastic composites with pressure-treated wood materials, and thus offered a practical way to recycle treated wood into value-added composites.

In this study, the optical and mechanical properties of polyurethane were improved by modified nanocrystalline cellulose (NCC). The surface of NCC was modified by 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-methacryloxy-propyltrimethoxysilane (MPS) to overcome the lack of compatibility with polyurethane. Polyurethane with modified NCC was characterized by wetting property, X-ray powder diffraction, and thermogravimetric analysis. The pencil hardness, specular gloss, and abrasion resistance of modified polyurethane were determined using the methods of Chinese National Standards GB/T 6739-2006, GB/T 9754-2007, and GB/T 1768-2006. The wetting property of NCC modified by GPTMS increased by 25.9%, and modification from MPS resulted in a 22.5% decrease of the contact angle. MPS-modified NCC affected the crystal structure and thermal stability of polyurethane more significantly than NCC modified by GPTMS. The pencil hardness of polyurethane was enhanced with 1.5% modified NCC. The specular gloss and abrasion resistance of modified polyurethane increased by 253.1% (1.0% NCC modified by GPTMS) and 59.4% (1.5% NCC modified by GPTMS), respectively. MPS-modified NCC led to the inconspicuous improvements.

In an effort to resolve problems related to the difficulty of degradation of the chelating agents EDTA and DTPA, this study used a kind of water treatment agent, 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP), as the chelating agent in the OPQP bleaching sequence of Acacia mangium kraft pulp. The Q stage was optimized with the use of response surface methodology (RSM) based on the Box-Behnken design (BBD). The results showed that the optimum chelating conditions for subsequent hydrogen peroxide bleaching were the following: Temperature of 54 °C, hold time 32 min, and dosage of agents 0.4%. These conditions resulted in the highest brightness value of 80.12% ISO and the selectivity coefficient of 0.46. Under these optimum chelating conditions, the results showed that the effect of HEDP in bleaching is better than that of EDTA with regard to viscosity of pulp, and that HEDP is similar to EDTA and DTPA in other properties.

Furfural residues produced from the furfural industry were investigated as a substrate for lactic acid production by simultaneous saccharification and fermentation (SSF). Alkaline peroxide was used for delignification of furfural residues to improve the final lactic acid concentration. The residue was treated with 1.3% to 1.7% hydrogen peroxide at 80 °C for 1 h with a substrate concentration of 3.33%. SSF of furfural residues with different delignification degrees were carried out to evaluate the effect of delignification degree on lactic acid production. Using corn hydrolysates/ furfural residues as substrates, SSF with different media were carried out to investigate the effect of lignin on the interaction between enzymes and lactic acid bacteria. Lactic acid bacteria had a negative effect on cellulase, thus resulting in the reduction of enzyme activity. Lignin and nutrients slowed down the decreasing trend of enzyme activity. A higher delignification resulted in a slower fermentation rate and lower yield due to degradation products of lignin and the effect of lignin on the interaction between enzymes and lactic acid bacteria. For the purpose of lactic acid production, a moderate delignification (furfural residues with the lignin content of 14.8%) was optimum.

This paper presents the development of particleboard based on common reed, reproducing the industry standard manufacturing process applied to wood chipboard. One of the main properties of the resulting board was its resistance to water, due to the hydrophobic properties of the common reed, despite there being no incorporation of melamine or any other waterproofing additive. The boards that were developed were analyzed using 2 mm and 4 mm sieves for fibre selection, a manufacturing pressure of 3 N/mm² and 25 N/mm², and a volume of urea formaldehyde resin content ranging from 5.2% to 13% (8 to 20% liquid format). Standard destructive tests were performed. It was found that under certain applied conditions, namely high pressure and adequate resin proportion (a pressure of over 3 N/mm² and over 15% liquid resin), Arundo donax L. particleboard demonstrated full recovery from the swelling test. This finding highlights an unmatched property in terms of recovery from the swelling test of the designed board. This property confers a interesting property to be used in high humidity environments without the need for special resin or waterproofing process.

The structural characteristics of corn stalks hemicelluloses during the active oxygen cooking process as a pretreatment of biomass conversion were investigated in this work. The hemicelluloses obtained from the corn stalks, pulp, and yellow liquor were evaluated by high-performance anion-exchange chromatography (HPAEC), Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and ¹H-¹³C 2D hetero-nuclear single quantum coherence (HSQC) spectroscopy. Based on the sugar and GPC analysis, FT-IR, and NMR spectroscopy, it could be concluded that the hemicelluloses were composed of backbones of (1→4)-β-D-xylopyranose substituted α-L-arabinofuranose and 4-O-methyl-α-D-glucuronic acid. During the cooking process, the hemicelluloses with more side chains were removed from raw material. The backbones were significantly damaged as well. Additionally, the ester linkages in the raw material were completely broken after the cooking.

An alkali-thermo-tolerant crude xylanase from Coprinellus disseminatus SW-1 NTCC1165 produced under solid-state fermentation conditions improves the brightness of sugarcane bagasse soda-AQ pulp by 7.3, 4.7, 6.1, and 8.2% in XODED, XOD(EOP)DP, OX(EOP)P, and XO(EOP)P bleaching sequences, respectively, at an enzyme dose of 8IU/g, a reaction time of 120 min, a consistency of 10%, and a pH of 6.4 at 55 °C. An improvement in brightness by 2.1% for pulp bleached by XO(EOP)P compared to OX(EOP)P sequence validates that xylanase treatment is more effective for hydrolysing lignin-carbohydrates complexes before oxygen treatment. AOX after XODED and XOD(EOP)DP sequences is reduced by 41.43 and 40%, respectively, compared to controls, but an increase in COD and color in studied bleaching sequences is attributable to the hydrolysis of hemicelluloses and the release of lignin-carbohydrates complexes after xylanase treatment. Xylanase treatment modifies fibre surface by introducing cracks, peelings, swelling, and external fibrillation, which facilitates faster penetration of bleach chemicals by disrupting physical barriers, as revealed by scanning electron microscopy.