Volume 8 Issue 4

Green vein is one of the most severe defects that affect wild cherry (Prunus avium L.). It consists of green streaks that alter the typical color and uniformity of the cherry wood, causing considerable value losses. A colorimetric analysis was performed on wild cherry clones using the CIE L*a*b* system, and the influences of environmental and genetic factors on green vein as well as the effects of the presence of green vein on the physical properties of the wood were investigated. Discriminant analysis shows that the color parameter that best discriminated green vein were low values of L* and a*. The cloning effect was the most important, but the environment also played an important role in the development of green vein. Finally, the presence of green vein was found to mainly affect the longitudinal shrinkage of wood and, to a lesser extent, wood density. These same features are typical of tension wood, to which green vein was strictly linked, as confirmed by some preliminary anatomical observations.

In this study, four species of wood-rot fungi—Piptoporus betulinus, Fomes fomentarius, Irpex lacteus, and Coriolus versicolor—were compared regarding their ability to degrade the wood of white birch and used to assess the degradation mechanisms. Chemical analyses were conducted following the Chinese national standard methods and included Fourier transform infrared spectroscopy (FTIR). The wood samples were inoculated with the four wood-rot fungi for a predetermined duration in the wood-decaying test. In the wood weight loss test, both F. fomentarius and P. betulinus showed the greatest reduction, but through different mechanisms: F. fomentarius mainly decomposed lignin, whereas P. betulinus mainly acted on cellulose. F. fomentarius, I. lacteus, and C. versicolor exhibited a shift at 3417 cm^-1 related to O-H stretching in hydroxyl groups, along with decreased absorption at 3410, 3406, and 3405 cm^-1, most likely due to the degradation of the related functional groups of lignin side chains. The wood decayed by P. betulinus displayed a change in the relative position of cellulose-associated bands at 1161 and 898 cm^-1. F. fomentarius can be considered a potential agent for the biopulping of white birch because of its high ability to degrade lignin, high holocellulose content, low content of 1% NaOH, and ethanol-benzene extractives.

Cationic dry strength agents (DSAs) are commonly used for paper strengthening. However, before they are applied, another chemical called an anionic trash catcher (ATC) is often used to pretreat pulp to neutralize the negative dissolved and colloidal substances (DCS), increasing the effectiveness of the subsequently added cationic DSA. However, in many cases, the negativity of the fibers is also neutralized by the ATC. Under such circumstances, it remains unclear to what degree the effectiveness of the DSA will be affected. In this paper, a deinked pulp was first pre-treated with a polyamine ATC; then, the effectiveness of two subsequently-added DSAs, anionic polyacrylamide (APAM) and cationic polyacrylamide (CPAM), were compared. Results showed that when the ATC was used alone, it deteriorated paper formation, resulting in a decrease of paper strength. When the DSAs were used alone, the CPAM was effective but the APAM was not. However, when the ATC was used to pretreat the pulp, the effectiveness of the CPAM clearly decreased, while that of the APAM clearly increased. The reason for this could be that the adsorption of APAM onto fibers was promoted by the pretreatment of ATC, possibly through the formation of an ATC and APAM polyelectrolyte complex.

The wet strength of handsheets subjected to dipping treatment by solutions such as glyoxal with Zn(NO3)2 as a catalyst, chitosan, and the crosslinking system of glyoxal and chitosan is studied in this paper. The crosslinking system achieved better wet strength performance than glyoxal or chitosan alone and slightly better than the sum of glyoxal and chitosan in the case of a curing temperature between 90 and 130 oC. However, handsheets treated by this crosslinking system became more brittle, which was shown by the reduction of folding endurance of the handsheets with increasing wet strength. The capillary rise and contact angle of the treated handsheets showed certain relations to their wet strength when the above solutions were used to improve the wet strength of the handsheets. The physical changes of the treated handsheets can provide evidence to explain the mechanism of wet strength development.

A simple electroless Ni-Cu-P plating process for preparing an EMI-shielding and corrosion-resistant wood-based composite has been developed. The effects of solution pH value on the metal deposition, surface resistivity, chemical composition, anti-corrosion properties, and crystal structure of the coatings were studied. The coatings were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. When the solution pH was increased from 8.5 to 10.0, the metal deposition increased decreased. Chemical composition indicated that the nickel deposition increased, whereas the opposite effect was obtained on copper and phosphorus elements with a pH increase from 9.0 to 10.0, and the crystal structure of the Ni-Cu-P coatings changed from an amorphous state to a microcrystalline one. Tafel curves of the Ni-Cu-P coatings prepared at pH 9.0 or 9.5 showed that they had excellent anti-corrosion properties in a 3.5 wt% NaCl solution. The morphology of the coating containing 69.86% Ni – 7.65% Cu – 22.49% P is superior to that with 75.99% Ni – 6.60% Cu – 17.41% P after corrosion tests. The plated birch veneers exhibited electromagnetic shielding effectiveness higher than 58 dB in frequencies ranging from 9 KHz to 1.5 GHz, and the coating firmly adhered to the wood surface.

A novel cationic amphiphilic lignin derivative with high surface activity was prepared from kraft lignin via the introduction of dehydroabietyl groups as lipophilic groups and diethylenetriamine groups as hydrophilic groups by the Mannich and ketone-amine condensation reactions. Solubility, surface tension, hydrophilic-lipophilic balance (HLB) values, foamability, and zeta potential were used to evaluate the basic physico-chemical properties of the cationic amphiphilic lignin derivative. The experiments show that the solubility of the cationic amphiphilic lignin derivative is 2.10 wt%, the critical micelle concentration is 5.0 g·L^-1, the surface tension is 29.85 mN·m^-1 at a concentration of 5.0 g·L^-1, the HLB value is 12, and the foam volume is 11.1 mL initially and 8.0 mL after standing for 5 min in an aqueous solution at pH 2.0.

Though there has been a great deal of work concerning the development of natural fibers in reinforced starch-based composites, there is still more to be done. In general, cellulose fibers have lower strength than glass fibers; however, their specific strength is not far from that of fiberglass. In this work, alpha-fibers were obtained from alpha-grass through a mild cooking process. The fibers were used to reinforce a starch-based biopolymer. Composites including 5 to 35% (w/w) alpha-grass fibers in their formulation were prepared, tested, and subsequently compared with those of wood- and fiberglass-reinforced polypropylene (PP). The term “high-performance” refers to the tensile strength of the studied composites and is mainly due to a good interphase, a good dispersion of the fibers inside the matrix, and a good aspect ratio. The tensile strength of the composites showed a linear evolution for fiber contents up to 35% (w/w). The strain at break of the composites decreased with the fiber content and showed the stiffening effects of the reinforcement. The prepared composites showed high mechanical properties, even approaching those of glass fiber reinforced composites.

Three aerobic lignin-degrading bacterial strains were isolated from palm oil plantation soils. The bacterial isolates were screened using a selective nutrient medium of minimum salt media (MSM), with kraft lignin as lignin substrate and methylene blue as the ligninolytic dye indicator. The newly isolated bacterial strains SHC1, SHC2, and SHC3 were found to have the potential to tolerate high concentrations of kraft lignin and produced all three main ligninolytic enzymes (lignin peroxidase, manganese peroxidase, and laccase); these strains may therefore be useful in the degradation of lignin in oil palm empty fruit bunch biomass. The production of ligninolytic enzymes was carried out by means of submerged fermentation for 7 days using 2 mm of oil palm empty fruit bunch (OPEFB) fiber as a substrate. These bacterial isolates were characterized using biochemical tests from Biolog and identified using 16S rRNA gene sequencing analysis, which identified the strains SHC1, SHC2, and SHC3 as Bacillus sp., Ochrobactrum sp., and Leucobacter sp., respectively with 99% sequence similarity. Bacillus sp. SHC1 produced the highest manganese peroxidase (MnP) of 2313.4 U/L on the third day and the highest lignin peroxidase (LiP) of 209.30 U/L on the fifth day of fermentation. The optimum pH and temperature for the production of ligninolytic enzymes by Bacillus sp. SHC1 were pH 8 and 30 °C.

In this study, oil palm empty fruit bunch (OPEFB) was treated with sodium hydroxide at room temperature and produced pulps with acceptable quality suitable for the making of commercial serviettes. The cold soda pulping of OPEFB was performed using various NaOH concentrations (1, 3, 5, 7, and 10%) for 24 hours using a liquor/OPEFB ratio of 8/1. The treated pulps were refined in 4 stages under atmospheric conditions by means of a Sprout Bauer disk refiner. The refined pulps were then screened and evaluated for their physical characteristics. The main pulp properties obtained were related to the caustic concentrations; higher caustic concentrations gave better properties. The measured pulp characteristics were: freeness 550-750 mL, sheet density 0.18-0.34 g/cm³, tear index 4.2-5.8 mN*m²/g, tensile index 3-20 N*m/g, and burst index 1.3-2.5 kPa*m²/g. In most cases the refining had little impact on pulp properties. The resulting cold soda OPEFB pulp treated with 3% caustic charge or higher showed good quality for serviette making.

A simple, green method was developed for the synthesis of silver nanoparticles (AgNPs) by using Dialdehyde Chitosan (D-CTS) as the reducing and stabilizing agent. D-CTS was prepared from the oxidation of chitosan by sodium periodate, and its degree of oxidation was determined by 1H-NMR and elemental analysis. The synthesized AgNPs were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The morphology and size distribution of the AgNPs were found to vary with the dialdehyde content of D-CTS and the pH value of the reaction solution. FT-IR spectra revealed that the aldehyde groups and the amino groups were the major agents that stabilized the AgNPs. XRD results indicated the presence of nano-silver having a face-centered cubic structure. SEM results showed that nano-silver particles of 30 to 40 nm in size were homogeneously dispersed in the solution. The possible mechanism of D-CTS on the reduction and stabilization of AgNPs may be due to the formation of four-coordinate complexes. The synthesized AgNPs remained stable for more than three months.