Volume 9 Issue 3

Esterified kraft lignins (KL) were prepared by reaction with maleic anhydride (MA), succinic anhydride (SA), and phthalic anhydride (PA) in acetone solutions. The esterified lignins were characterized using ATR-FTIR, solid state CP-MAS 13C NMR spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). PA modification resulted in the highest weight gain percent (WGP) when compared to MA and SA modifications. Spectroscopic analysis revealed decreases in hydroxyl content and increases in carbonyl (C=O) and ester groups of the modified KL as a result of esterification. The hydrophobic properties of the modified lignin increased. The MA- and SA-modified KL showed an increased thermal stability compared to unmodified KL. PA-modified lignin presented distinct thermal decomposition stages, which showed rapid degradation at lower temperature. The results of this study indicate that it is possible to change the basic properties of kraft lignin by anhydride modification to facilitate the production of high performance composites.

In the past few decades, the use of glass fiber-reinforced polymers (GFRP) to enhance the strength and stiffness of timber beams has been established. Research to predict the performance of structural timber is ongoing. Nondestructive evaluation of its dynamic performance and reliability are important. A nondestructive testing method based on fast Fourier transform analysis was used to establish the dynamic modulus of elasticity of GFRP-reinforced timber beams. The results were compared to those obtained via destructive measurements of the static modulus of elasticity using a regression analysis method. Significant correlations between the dynamic modulus of elasticity (MOE) and static MOE indicate that nondestructive testing is a suitable tool for practical use. Reinforced timber beams were designed based on the measured dynamic MOE. Orthogonal theories were used to analyze the effects of the thickness, glue application, and surface area of GFRP on the MOE of reinforced timber beams. Furthermore, the system reliability of GFRP-reinforced timber beams was predicted with a finite element model. The results showed that GFRP can significantly increase the reliability of structural lumber.

The bending stiffness of pulp fibers in both dry and wet states is of great importance with respect to many optical and physical paper properties. We introduce a method that evaluates fiber bending stiffness from the fibers’ Young’s modulus (E) and the area moment of inertia (I) from the fiber cross section. The values for E and I in the dry state are obtained from single fiber tensile testing and image analysis of the fiber cross section. The values for the wet state are estimated from literature results for decreasing elastic modulus due to wetting and by the measurement of swollen, freeze-dried fiber cross sections by serial sectioning. We show a comparison between the results from our method and the bending stiffness of individual fibers measured with other methods.

Lab-processed cellulose nanofibrils (CNF-L), commercial cellulose nanofibrils (CNF-C), and cellulose nanocrystals (CNC) were used in this study as reinforcing materials in phenol formaldehyde (PF) resin. The mechanical modification of adhesives and cell wall layers (S2 and compound corner-middle lamellae [CCML]) by the three types of cellulose particles was investigated by nanoindentation. Results showed that cellulose nano-materials can improve the mechanical properties of both adhesives and the cell wall structure. CNF-C had the most obvious reinforcing effect on the elastic modulus (Er) and hardness within the glue line. With modification, the Er and hardness reached 13.0 and 0.436 GPa, respectively, in the S2 layer far from the glue line. In comparison, the control sample had an Er and hardness of 7.31 and 0.256 GPa, respectively.

This study focuses on the development of epoxy/luffa composites and the investigation of their mechanical and acoustical properties. The fibers underwent an alkalization treatment, and its effects on the mechanical and sound absorption properties of the composites were measured utilizing a universal testing machine and two-microphone transfer function impedance tube methods. The effects of chemical modifications on the fibers were studied using a scanning electron microscope (SEM). The thermal analyses of composites were conducted using thermo-gravimetric analysis (TGA). The composite’s functional group was identified and evaluated using Fourier transform infrared spectroscopy (FTIR). The sound absorption coefficient of untreated and treated composites across a range of frequencies was very similar. Untreated composites appeared to perform better than those that were treated. Compared with untreated fiber composites, there was an improvement in the tensile strength of the treated fiber composites. The SEM characterization showed that the alkaline treatment changed the morphology of the fibers, resulting in a decrease in the sound absorption coefficients of the composites. The thermal characterization of composites showed that dehydration and degradation of lignin occurred in a temperature range of 40 to 260 °C, and the maximum percentage of cellulose was found to decompose at 380 °C.

Fully degradable poly(L-lactic) acid (PLLA) and lignin blends were prepared using the melt blending method. The impact strength of PLLA was dramatically improved by 52.4% and 36.6% with the addition of 5 wt% and 10 wt% of lignin, respectively. Meanwhile, the Young’s modulus was maintained. Polarized optical microscopy (POM) results indicated that lignin served as a nucleating agent for the heterogeneous crystallization of PLLA in blends, which was responsible for the improvement in the impact strength. The introduced lignin also promoted the cold-crystallization of PLLA, which was demonstrated by differential scanning calorimetry (DSC). The blends of PLLA with lignin are considered to be a promising material because of the improved toughness, the full degradability, and the lower price compared with pure PLLA.

In this study, three different sealants (gelatinized starch (GS), gelatinized starch/wood flour mixture (GSWF), and soy-protein adhesive (SPA)) were used to seal the lathe checks in veneers before applying phenol formaldehyde adhesive. The shear strain distribution on the interphase of the lap joint specimens was measured by a digital image correlation technique. The results showed that the average shear strain along the bond line on the interphase was 1.94×10^-3 when the specimen had lathe checks. Sealing treatment can thus reduce the average shear strain effectively. Soy-protein adhesive seemed to have the greatest ability to decrease the average shear strain along the bond line, from 1.94×10^-3 to 0.94×10^-3. In contrast, gelatinized starch appeared to decrease the strain slightly to 1.61×10^-3. Average shear strain along the bond line of specimens treated with gelatinized starch/wood flour mixture was 1.00×10^-3, which was between the values of the other two sealants. Dry shear strength of samples treated by GS and SPA increased from 7.6 MPa to 9.65 MPa and 8.85 MPa, respectively. The mixture of GSWF decreased the strength to 6.32 MPa. Wet strength of treated samples were smaller than untreated ones.

Ganoderma lucidum has a well-developed ligninolytic enzyme system, where laccase is the dominant and sometimes only synthesizing enzyme, and therefore could find an application in the delignification of abundant plant raw materials and in food, feed, paper, and biofuel production. The questions that provided the goals for the present study were whether the profile of G. lucidum laccase depends on cultivation type and carbon source, as well as whether intraspecific diversity exists. Conditions of submerged cultivation proved more preferable for laccase activity compared with solid-state cultivations in all studied strains, while oak sawdust provided a better carbon source than wheat straw. Maximum laccase activity (7241.0 U/L) was measured on day 14 of oak sawdust submerged fermentation by strain BEOFB 431. Intraspecific diversity in synthesized proteins was more significant in wheat straw than in oak sawdust submerged fermentation. The profile of laccase isoforms was dependent on strain, plant residue, type, and period of cultivation. Four acidic laccase isoforms (pI 3.6) were detected in G. lucidum BEOFB 431 at the same cultivation point where maximal enzyme activity was measured.

This work analyses the anti-fungal efficacy and stability of 10 essential oils, as well as their colour stability, in wood. The efficacy of oils against the decay fungi Coniophora puteana and Trametes versicolor as well as the moulds Aspergillus niger and Penicillium brevicompactum was evaluated first on filter papers treated with 1, 3.5, 10%, or 100% concentrate, and then on beech wood treated with 10% solutions. Accelerated ageing of treated beech samples was done before mycological tests and consisted of heating, leaching followed by heating, and Xenotest followed by heating. The highest growth inhibition of moulds and C. puteana was caused by thyme, oregano, sweet flag, and clove oils, while the savory and birch oils were less effective. These oils are potentially useful for wood protection against brown-rot fungi and moulds, mostly in interior conditions. The essential oils had only a negligible effect against the white-rot fungus T. versicolor, which was more apparent after previous ageing of wood. Some essential oils with a yellow tone (birch, oregano, sweet flag, savory, and tea tree oils) significantly changed (p<0.05) the natural colour of beech wood, but the new colours were relatively stable and underwent only mild changes after accelerated ageing in Xenotest.

In this paper, a kinetic model of the first chlorine dioxide bleaching stage (D0) in an elemental chlorine-free (ECF) bleaching sequence is presented for bagasse pulps. The model is based on the rate of adsorbable organic halogen (AOX) formation. The effects of the chlorine dioxide dosage, the sulfuric acid dosage, and the reaction temperature on the AOX content of wastewater are examined. The reaction of AOX formation could be divided into two periods. A large amount of AOX was formed rapidly within the first 10 min. Ten minutes later, the AOX formation rate significantly decreased. The kinetics could be expressed as: , where W is the AOX content, t is the bleaching time (min), T is the temperature (K), is the dosage of chlorine dioxide (kg/odt), and is the dosage of sulfuric acid (kg/odt). The fit of the experiment results obtained for different temperatures, initial chlorine dioxide dosages, initial sulfuric acid dosages, and AOX content were very good, revealing the ability of the model to predict typical mill operating conditions.