Volume 14 Issue 4

Enzymatic degradation products of lignin, having potential for added value, were obtained by extraction and subsequent enzymatic treatments of oil palm empty fruit bunch (OPEFB). The objective was to optimize the production of OPEFB lignin degradation products and study the effects of different enzymes and reaction media. Powder of OPEFB lignin was recovered from organsolv black liquor by using methanol, acidified water, and deionized water, respectively. OPEFB lignin was later subjected to enzymatic hydrolysis in an incubator shaker for 24 h using laccase and cutinase in various reaction media, including phenol, water, and acetate buffer. Nine compounds were recovered as OPEFB lignin degradation products, namely hydroxybenzoic acid, hydroxybenzaldehyde, vanillic acid, vanillin, syringic acid, syringaldehyde, coumaric acid, ferulic acid, and guaiacyl alcohol. When laccase was used in water, the product with the highest concentration was syringaldehyde (4061.1 ± 89.9 mg/L), and followed by hydroxybenzoic acid (1029.8 ± 50.2 mg/L). Vanillic acid was the product with the highest concentration (126 ± 97.5 g/L) found when laccase was used in phenol. When cutinase was used in water, products with the highest concentrations in the medium were syringaldehyde (4837.6 ± 156.4 mg/L) and syringic acid (2387.7 ± 105.3 mg/L). High performance liquid chromatography (HPLC) was used to quantify the OPEFB lignin degradation products.

The pulping of birch wood using dilute aqueous nitric acid solution under atmospheric pressure was studied. The pulping conditions, delignification reaction course, and waste-liquid recovery were studied in detail. The optimum cooking conditions were 9.2% nitric acid for 4.3 h at 85 °C. The pulp yield at these conditions was 51.1%, the lignin content was 5.1%, and the brightness was 50%. The delignification course during the pulping involved two phases, namely, bulk and residual phases. The bulk phase was 0 to 1.5 h long, and the delignification level was 92.6% of the total dissolved lignin. The residual phase was 1.5 h to 4.5 h long, and the delignification level reached about 7.4% of the total dissolved lignin. The waste liquid could no longer be used after six rounds of recycling. The contents of nitrogen and organic matter in the organic fertilizer prepared using the final-round of recycled waste liquid were in line with the indicators for the preparation of organic fertilizer.

In order to detect the size and shape of defects inside wood, a propagation velocity model of stress wave in the longitudinal section of trees in different direction angles was proposed and evaluated. The propagation velocity model was established through theoretical analysis. Four representative tree species in the northeast region of China were taken as test samples. The propagation velocity of stress wave in the longitudinal section of trees in different directions was measured using a nondestructive testing instrument. The corresponding regression model was obtained, which was in good agreement with the theoretical mathematical model. For the larch log samples, a healthy multiple regression model (z = 109.2×2 – 182.1y2 + 36.78x2y2 – 34.76x2y4 + 1627) with correlation coefficient R2 = 0.97 and root mean square error RMSE =17.81 was used to conduct two-dimensional imaging of defective logs. Based on the results of two-dimensional imaging, the highest fitness of the images was 94.24%, and the lowest error rates of defect cavities was 6.11%. The imaging results showed that this method accurately detected the internal defects of trees and was not affected by the size of defects.

Sodium carboxymethyl cellulose (CMC) is a major cellulosic derivative that has a wide variety of applications. The solubility of CMC is affected by the degree of substitution (DS) of carboxymethyl groups and their distribution along the CMC molecular chain. In this study, an enzymatic hydrolysis technique was used to determine the distribution of carboxymethyl substituents. Two key parameters, namely the average length of the molecular chain segments not susceptible to enzymatic hydrolysis by cellulases (L ̅Sn, including chains fully substituted or containing single unsubstituted unit) and the average length for the molecular chain segments susceptible to enzymatic hydrolysis (L ̅Gn, unsubstituted chains segments), were obtained. This approach was subsequently applied to characterize four CMC samples having similar DS values (~0.80). The distributions of carboxymethyl substituents along the CMC molecular chain were found to be drastically different. The L ̅Sn varied from 9.6 to 49.5, while the L ̅Gn was almost constant (from 4.5 to 5.4). This information was correlated to the CMC solubility. The swelling ratio and the dynamic contact angle revealed that the CMC samples with higher L ̅Sn exhibited stronger swelling and wettability than those with lower L ̅Sn. The dissolving time of the CMC molecule decreased substantially with the increase in L ̅Sn.

The effect of nanofibrillated cellulose (NFC) was investigated relative to the strength of chemi-mechanical pulp (CMP) and paper. The NFC was added at five levels: 0%, 2%, 4%, 6%, and 8%. Handsheets with a basis weight of 60 g/m2 were prepared, and the physical properties (air resistance and surface roughness), the mechanical properties (tensile strength, burst strength, and tear strength), and the optical properties (brightness, opacity, and yellowness) were measured according to TAPPI standards. By increasing the NFC content, the tensile strength, burst strength, air resistance, brightness, and whiteness increased by 10.9%, 12.5%, 23.6%, 0.6%, 3.5%, and 6.8%, respectively, compared to the control (0% NFC) samples. By increasing the NFC content, the tear strength, roughness, and opacity decreased by 10.4%, 11.1%, and 0.6% compared to the control samples.

A three-component flame-retardant system was prepared based on in situ polymerization of ammonium polyphosphate (APP), diatomite (DE), and aluminium trihydroxide (ATH) to improve the flame retardance and smoke suppression properties of fibrous materials. Compared to the two-component system of APP-DE, the addition of APP-10% DE-4% ATH dosed at a filler load of 20% of the fibrous material reached a limited oxygen index of 27.5%, which was approximately 9.1% higher than the two-component system. The lower mass loss rate and higher residual mass at high temperatures resulted in excellent flame retardance. The synergistic effect on alleviating combustion and reducing heat release was shown by the 16.6%, 22.1%, and 12.5% decreases in the peak heat release rate, total heat release, and average effective heat combustion, respectively. Superior fire resistance was demonstrated by a higher fire performance index and a lower mass loss. A smoke suppression effect was shown by the peak smoke release rate and the total smoke release results that were 28.7% and 15.8% lower than the two-component system, respectively. Based on the porous structure of DE and generated aluminum oxide (Al2O3), the outstanding adsorption effect and flame-retardant effect was also demonstrated by the production rate of carbon monoxide (CO) and carbon dioxide (CO2).

Four additives including two specimens of kaolin clay, limestone, and a byproduct of a sugar mill (BSM) (mainly CaCO3) were utilized to increase ash fusion temperature (AFT) of corn straw. The results showed that the ash softening temperature (ST) was increased by 250 to 380 °C and agglomeration or slagging could be avoided during combustion with each additive. Meanwhile, the slagging/fouling tendency of all ash samples fell within the “low” range according to alkali index. Lime was shown to have the best effect, which indicated that calcium oxide was the best compound to increase the AFT of corn straw densification (CSDF). Both kaolin specimens made the fusion range very narrow. BSM had the least effect on ST among the four. All the additives diluted the concentration of chlorine by more than 50%. No agglomeration or slagging phenomenon appeared in real boilers burning CSDF with lime blended as additive.

Recently, enhancing the performance of polyurethane (PU) coatings with cellulose nanomaterials (CNM) has been actively researched. Cellulose nanomaterials exhibit considerable potential to increase the mechanical strength of PU coatings due to their high aspect ratios and elastic moduli. In this study, PU reinforced with CNM was coated onto paper to enhance the paper’s mechanical strength and soiling resistance. To investigate the reinforcing effect, two different CNM, cellulose nanocrystals (CNC) and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibers (TOCN), were selected, and suspensions with different ratios of PU and CNM were prepared. After coating the paper with each of them, the mechanical properties of the paper, including tensile strength, folding endurance, and soiling resistance, were evaluated. The mechanical strength and anti-soiling performance of the PU-CNM coated papers were greatly enhanced. Especially, PU-TOCN had superior properties as a durable paper coating despite a low TOCN concentration, less than 2%, because the TOCN crosslinked with PU via polyaziridine. Furthermore, the PU-CNM coating protected the paper from being contaminated, which was confirmed by scanning electron microscopy and energy dispersive X-ray mapping. Consequently, durable paper exhibiting soiling resistance was fabricated by coating the paper with PU-TOCN suspensions.

The effect of the end distance was studied relative to the static ultimate lateral load capacity of a single-shear unconstrained wood-plastic-composite-to-metal single-bolt connection (SUWSC). Equations estimated the static ultimate lateral loads of the SUWSCs that failed during the end tear-out, splitting, and yield modes and were obtained using stress concentration factor regression- and mechanics-based approaches. The experimental results showed that the stress concentration factor was a linear function of the end-distance to bolt-diameter ratio for the SUWSCs that failed during end tear-out and splitting modes. The static ultimate lateral loads of the SUWSCs that failed during the yield modes were estimated using a mechanics-based equation. The minimum end distance for the SUWSCs that failed without end fracture (i.e., only with yield mode) was 25.4 mm, which was four times larger than the bolt diameter.

Epoxidized jatropha oil (EJO) was investigated as a sustainable alternative to petrochemical-based plasticizers to reinforce the plastics, leading to increased ductility and toughness of kenaf-reinforced poly(lactic acid) (PLA). The EJO was melt-blended into kenaf-reinforced PLA at concentrations from 1 wt% to 5 wt%. The blends were then hot-pressed into sheets to characterize their mechanical and physical properties. Kenaf fibers were treated with 6% sodium hydroxide (NaOH), and the effects thereof on the composites’ tensile, flexural, and impact properties, as well as their water absorption and density were stu died. The impact strengths of the kenaf-reinforced PLA composites were improved with the addition of EJO up to 5 wt%, with a maximum over 10 times that of the neat PLA. The flexural strength and modulus increased 4% and 50%, respectively, for treated kenaf-reinforced PLA plasticized with EJO. This increase demonstrated the alkalization treatment’s notable improvements to the composites’ properties. Furthermore, analysis by scanning electron microscopy (SEM) of the composites’ tensile fracture surfaces indicated better interaction adhesion of the treated kenaf-reinforced PLA plasticized with EJO compared with the untreated composites. Compared to untreated 1 wt% EJO biocomposites, the treated 5 wt% EJO biocomposites reduced water absorption from 3.1% to 1.6% after 8 weeks of immersion.