Volume 10 Issue 2

Kraft lignin was used to prepare kraft lignin-N-isopropyl acrylamide hydrogel (KNIAH). The results indicated that using a 1:2 mass ratio of KL-to-N-isopropyl acrylamide (NIPAM), 48 h reaction time, and 1.5 mL of crosslinking agent yielded KNIAH with the maximum swelling degree (209.3%). The crosslinking reaction was verified by C-N shifting at 1272 cm-1 and increased C=O bonding at 1720 cm-1. KNIAH with a smooth and uniform surface was created. DSC demonstrated that free water combined with KNIAH at 200 °C, after which KNIAH began exothermic decomposition. TGA shows that KNIAH with good performance of heat resistance and degradation. Absorption was maximized at 20 °C; low temperature and neutral solution was conducive to water absorption. Decolorization increased with decreasing concentration and pH value.

Starch-based adhesives were developed by hydrolyzing starch with polyvinyl alcohol under alkaline and acidic conditions at various treatment temperatures. The chemical and physical structures of the corn starch and hydrolyzed starch were characterized with Fourier Transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and scanning electronic microscopy (SEM). Thermal degradation and bond strength were also evaluated. The results indicated that the bond strength of starch adhesives reached a maximum value at 40 °C. The FI-IR results showed that the amount of hydroxyl groups first increased and then decreased with increasing treatment temperature. When the treatment temperature was 55 °C the crystallinity of treated starch was the lowest and the thermal resistance also the weakest; it decreased by 10.1% and 13.6% respectively compared to untreated starch. Obvious erosion could be observed from the SEM images of treated starch. In addition, the interaction of polyvinyl alcohol (PVA) and starch also could be observed, and the results indicated that the compatibility between starch and PVA became better and better as the treated temperature was increased.

Eucalyptus regnans was subjected to thermal treatment. The samples were placed in superheated vapors at 120, 130, 140, 150, 160, 170, 180, 190, and 200 °C at ambient pressure to determine the effect of heat treatment on the physical-mechanical properties of Eucalyptus regnans. The results showed that heat treatment played an important role in the impact toughness, nail-holding ability, surface hardness, bending strength, and bending modulus of elasticity of E. regnans. The nail-holding ability, surface hardness, bending strength, and bending modulus of elasticity of E. regnanstreated at 120 and 130 °C increased related to untreated wood, but decreased at 140 to 200 °C. The impact toughness decreased after heat treatment from 120 to 200 °C, while the bending modulus of elasticity increased. Consequently, heating at 120 and 130 °C was found to be more suitable to ensure sufficient strength.

In this study, a new technical process for hardening wood fiber insulation boards is introduced. During the dry-process, the fibers are usually glued with polymeric-diphenylmethane-diisocyanate (pMDI) and hardened to wood fiber insulation boards using a steam-air mixture. However, the maximum temperature reached in the steam-air process was 100 °C, and it was impossible to use an alternative binding agent for the gluing of the wood fiber insulation boards other than pMDI. When incubated with laccase-mediator-system (LMS) as a naturally based bonding system, temperatures of over 120 °C are required because of the chemical wood composition, especially the lignin. In this case, the hot-air/hot-steam process offers new technical opportunities for realizing temperatures above 100 °C. In this study, wood fiber insulation boards were glued with LMS, vs. reference boards with inactivated LMS, laccase alone, and 4% pMDI. Then, the boards were hardened using one of three processes: with steam-air mixture, with hot-air, and with hot-air/hot-steam. Through the hot-air/hot-steam process, temperatures of well over 120 °C were attainable. All the insulation boards hardened using the hot-air/hot-steam process showed better physical and technical properties than those hardened with steam-air mixture or hot-air alone. The reason for this is a sudden increase of temperature after the adding of steam because high temperatures insure that the LMS activated wood fiber surface lignins are completely plasticized. As a result the physical-technological properties such as internal bond strength, compression strength, and short term water absorption of insulation boards treated with LMS were comparable to those boards treated with 4% pMDI.

Water retting is a traditional retting method that enables the low-cost production of bast fibers. This study investigated the retting of flax straws by distilled water for three different durations at room temperature in laboratory condition. The retting quality was evaluated in terms of the weight loss and degumming rate together with the fiber properties, which included color, linear density, and tensile properties. The degumming rate was defined as the percentage change in pectin content of phloem regions from the raw flax to water-retted flax. It was found that the dissolution of pectin and other contaminating materials during the beginning retting stage must have played an important role in pectin (content) and weight loss besides pectin degradation, and water retting gradually improved both the apparel properties, such as whiteness and fineness, and the mechanical properties of the fibers. Given the results, a water retting duration of six days should be sufficient to provide sound retting efficiency and reasonable fiber properties.

A native strain of Pycnoporus sanguineus (CS2) was selected because of its lignocellulolytic potential on a color-based agar plate screening system; pectinolytic and amylolytic capabilities were also assessed. The effects of different lignocellulosic substrates under submerged cultures of selected fungi on the enzymatic production of cellulases, xylanases, amylases, and laccases were evaluated. Seven different treatments, in which different combinations of wheat straw (WS), wheat bran (WB), orange peels (OP), grapefruit peels (GP), and apple peels (AP) were used, were established. Controls of 2% (w/v) carboxymethyl-cellulose (CMC) and xylan were used in a rich medium for basidiomycetes (RMB). The highest titers were achieved using OP-based cultures, with large titers of CMCases (33.5 U), avicelases (15.7 U), ß-D-glucosidase (72.9U), and xylanases (18.3 U). The best levels of amylase and laccase activity were obtained in the RMB plus CMC (RMB-CMC) (7.2 U) and in the medium OF/AP/GP (6.4 U), respectively. The relative molecular sizes of cellulase, xylanase, and amylase were 66.2, 56.5, and 90.8 kDa, respectively. Laccase and amylase had maximum activities at 60 °C whereas cellulase and hemicellulase had maximum activities at 70 °C. The optimal pH for cellulases, xylanases, and amylases was 5.0 in every case, and more than 95% activity was observed at pH 6. These results reveal some efficient operating parameters for the application of these enzymatic extracts as adjuvants to improve animal nutrition.

Consecutive superheated steam-alkali treatment was introduced to modify oil palm mesocarp fiber (OPMF) prior to biocomposite fabrication. The biocomposite made up of 70 wt.% modified OPMF (SNOPMF) and 30 wt.% poly(butylene succinate) (PBS) was prepared by melt blending followed by compression molding. A silane coupling agent of 3-aminopropyltrimethoxysilane (APTMS) was also incorporated into the SNOPMF/PBS biocomposite during the compounding process to impart better adhesion at the SNOPMF-PBS interface. The experimental results revealed that the tensile, flexural, and impact strengths were enhanced by 16, 30, and 15%, respectively, after the introduction of 2 wt.% APTMS to the SNOPMF/PBS biocomposite. Similarly, the resistance to water uptake and thickness swelling of this biocomposite was improved by 34 and 49%, respectively, relative to SNOPMF/PBS biocomposite. The SEM observation of the tensile fracture surface showed that APTMS improved the interfacial adhesion between SNOPMF and PBS. Based on the results, it can be deduced that APTMS could be a good coupling agent for improving the SNOPMF-PBS adhesion and, thereby, lead to a water resistant biocomposite of enhanced mechanical properties.

Failure criteria from six theories were applied to estimate the shear strength of the adhesive line in terms of grain slope when under loaded tension stress. The shear stresses of the adhesive line as a function of the angle of the wood grain were determined by experimental tests. Specimens were obtained from 12 Eucalyptus saligna wood beams. They were prepared with varying angles of the grain (0°, 15°, 30°, 45°, 60°, 75°, and 90°) in relation to load application, following the requirements of the Brazilian standard. From the results of the six failure criteria and experimental results, robust statistical analysis was carried out; it was thus possible to adapt the models to determine the shear strength of the adhesive line as a function of the angle of the wood grain. The six mathematical models evaluated do not show statistical significance (p < 0.05) in their original format. With modifications, the models showed statistical significance only with the formulations of DIN 1052 and Karlsen.

Airflow and the type of biomass are the two most important factors influencing the performance of a biomass gasifier. In this research, the effects of air flow rate (air-fuel equivalence ratios of 0.21, 0.25, and 0.29) and biomass type (woody biomass, agricultural residue, and perennial grass) on the performance of an updraft biomass gasifier were evaluated based on its tar and producer gas generation. It was found that increasing airflow increased the formation of tar species for all biomass types studied, but no significant differences in producer gas composition were found when the air-fuel equivalence ratio was changed. Thus, air-fuel equivalence ratios ranging from 0.21 to 0.25 were deemed appropriate for minimal tar generation. The results also showed that different biomass types generated producer gas with significantly different tar contents: woodchips yielded the most tar, followed by sorghum stover and prairie hay. The higher heating value of producer gas from various biomass types was also significantly different. Wood chip-derived producer gas had the greatest higher heating value, followed by prairie hay and sorghum stover. The carbon monoxide content in the produce gas of the three biomass types also exhibited significant differences with varying biomass type, similar to the higher heating value, but there were no significant differences in the H2 content with varying biomass type or airflow.

Xylanase, pectinase complex, and BL11 pectinase were employed for the pretreatment of gampi and paper mulberry bast fiber pulps prior to chlorine dioxide bleaching. The bleaching efficiencies of the pulps with different enzymatic pretreatments were investigated. Accelerated aging by heat-humidity treatment was also conducted to evaluate yellowing phenomena and to estimate the prevention of brightness reversion (brightness retention) by enzymatic pretreatment. The order of active chlorine required with respect to pretreatment was pectinase complex > xylanase > BL11 pectinase for soda and soda/oxalate gampi pulps and pectinase complex > BL11 pectinase > xylanase for soda and soda/oxalate paper mulberry pulps. Higher brightness retention values were observed for soda/oxalate pulps compared to soda pulps. The brightness retention levels for gampi pulps and mulberry pulps after ClO2 bleaching with enzymatic pretreatment were higher than the levels of ClO2 and NaClO bleaching pulps. Enzymatic treatments were thus able to reduce the usage of ClO2 and to assist in producing photo-stable paper materials for art and artifact-repairing applications. Thus, enzymatic pretreatment of the pulp has the potential to meet world trends and environmental sustainability for pulp and paper industries.