Research Articles

Enzymatic/Mild Acidolysis Lignin (EMAL) was isolated from Cunninghamia lanceolata and eucalyptus woods. The chemical structure and thermochemical properties were characterized by means of elemental analysis, Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TG), and pyrolysis-gas chromatography combined with mass spectrometry (Py-GC/MS). The EMAL isolated from Cunninghamia lanceolata (C-EMAL) had larger HHV (higher heat value) in comparison to the EMAL isolated from eucalyptus (E-EMAL) due to the greater carbon content of the C-EMAL. The E-EMAL had more syringyl units, whereas the C-EMAL contained more guaiacyl units. It was observed that thermal decomposition occurred over a wide temperature range, and that at a given starting temperature, within the same sample, a higher heating rate produced a higher temperature at which maximum weight loss peaked. The pyrolysis products were mainly composed of carboxylic acids, alcohols, ketones, aldehydes, olefins, alkanes, esters, ethers, and phenols. At all pyrolysis temperatures, the largest components of the pyrolysis products obtained from C-EMAL were the phenols.

The properties of non-treated and hydrochloric acid (HCl)-treated oil palm ash (OPA)-filled natural rubber (NR) composites were investigated in terms of swelling behavior, rubber-filler interaction, ageing resistance, dynamic mechanical analysis, and thermal stability. The incorporation of OPA resulted in a lower degree of swelling in the NR composites, which was even lower after HCl treatment. Concerning the rubber-filler interaction, the HCl-treated OPA had better interfacial interaction with the NR matrix than that of non-treated OPA, resulting in higher crosslink density and improved ageing resistance. The dynamic mechanical properties of NR composites were better with the incorporation of HCl-treated OPA compared to non-treated OPA, in that they showed a higher storage modulus and lower mechanical loss factor. Thermogravimetry analysis revealed that the HCl treatment process did not affect the thermal stability of OPA-filled NR composites.

The effects of ground calcium carbonate (GCC) modification through the polyelectrolyte multilayering technique on deposition kinetics were investigated. The surface charge of GCC particles was changed from negative to positive through Layer-by-Layer (LbL) multilayering with polyelectrolytes on GCC particles. The LbL multilayered GCC particles could deposit onto negatively charged cellulose fibers due to electrostatic attraction. Deposition kinetics followed modified Langmuir kinetics, which describe the dynamic equilibrium of deposition and detachment of the particles. The multilayer that had more affinity to the fibers had the higher deposition rate constant. The multilayer with a branched polyelectrolyte showed a low detachment rate constant compared to the linear polyelectrolyte, which led to a high equilibrium deposition amount for the particle. Application of high shear had adverse effects on deposition. However, LbL multilayered GCC particles showed reversible deposition characteristics after lowering the stirring speed.

Brazil is the world’s largest producer of charcoal, mainly for the steel industry. Fresh wood has high moisture content, which reduces its use for energy. Thereby, drying is a fundamental step for charcoal production. This work aimed to determine longitudinal variation in stem diameter, wood basic density, moisture content, and calorific value of Eucalyptus urophylla and Corymbia citriodora logs. These logs were taken from different longitudinal positions on the trees and dried for 90 d; the net calorific value was determined based on the gross calorific value and moisture content. Curves and models were generated based on this data for moisture content and net calorific value during the 90-d period. The logs from the base and middle of C. citriodora trees had lower initial moisture content, and, after 90 d of drying, all logs from the top reached the equilibrium moisture. Drying the logs increased the wood calorific value, with an increase of 49.36%, 63.86%, and 85.98% for those of the base, middle, and top, respectively. The models generated had a high coefficient of determination and a low standard error.

Torrefaction of sawdust has the advantages of increasing its heating value, lowering its O/C ratio, and making it more convenient to transport and crush. Torrefied sawdust has characteristics that are more similar to coal than to sawdust. The initial pyrolysis temperature and residue content of torrefied sawdust are higher than those of sawdust. With the increase of coalification degree of three different coals, the initial pyrolysis temperature and residue contents are raised. The initial pyrolysis temperatures and remaining contents of lignite, bituminous coal, and anthracite are 330, 380, and 500 °C and 61.3, 75.1, and 89.5%, respectively. The torrefied sawdust also has a synergistic effect on the conversion of anthracite and bituminous coal, but it has an inhibitory effect on lignite. The composition of gaseous products was also measured after pyrolysis. The results demonstrate that with the addition of torrefied sawdust to anthracite and bituminous coal, the gaseous products contain more combustible components, such as H2, CO, and CH4, which increase the heating value. Moreover, the effect is more obvious with the co-pyrolysis of torrefied sawdust and anthracite. However, the co-pyrolysis of torrefied sawdust and lignite leads to decreasing CO and light hydrocarbons (CnHm (n=1, 2)) in the resulting gaseous products, which has a negative effect on the quality of the gaseous products. The co-pyrolysis characteristics of torrefied sawdust with different rank coals are discussed in this paper.

Poly-epichlorohydrin-dimethylamine (p-DMA-co-ECH) was synthesized and was used to modify bleached eucalyptus kraft pulp (BEKP). The modified pulp (designated PDMAECH pulp) was characterized by zeta potential, FTIR, NMR, and SEM. Both the PDMAECH pulp and the BEKP were used as adsorbents to remove Acid Scarlet G (ASG) from aqueous solution. The effects of operational parameters on the efficiency of dye removal, including pH, adsorbent dosage, initial dye concentration, and contact time, were investigated. Results showed that modification could change the surface characteristics and effectively enhance the adsorption capacity. The optimum pH for ASG removal with the modified bleached eucalyptus kraft pulp (PDMAECH pulp) was found to be 4.0, and for BEKP it was 2.0. Under the optimized conditions, the maximum capacities for ASG adsorption were also investigated. The adsorption processes of both adsorption reactions were spontaneous and exothermic, and the adsorption capacities decreased with an increase in temperature. Freundlich and Langmuir models were used to analyze the obtained experimental data. The Langmuir model was found to be a better fit for the experimental data for both adsorbents. Kinetic studies showed that the rate of adsorption of ASG on both adsorbents obeyed a pseudo-second-order kinetics model. The desorption process for PDMAECH pulp was also explored.

Birch sawdust was extracted with a pressurized hot water (PHW) flow-through system. The pH of the extract was controlled during extraction by the addition of acetic acid/sodium acetate buffer. Three different pH levels, 4.0, 4.2, and 4.6, were used. Extraction temperatures were 160, 170, and 180 °C, with a constant 4 mL/min flow rate through the 50 mL extraction vessel. During PHW extraction with plain water, the end pH of the extract dropped from 5 to below 3. Buffers kept the pH of the extracts constant during the first 30 min of extraction. Compared to plain water, the use of buffers resulted in a lower yield of xylans during the 170 °C extraction. However, with the buffered system it was possible to obtain xylans from sawdust with a higher molar mass than plain water extraction. Acetic acid/sodium acetate buffer enabled control of the hydrolysis rate of xylans during extraction.

Kenaf (Hibiscus cannabinus), a fast-growing fiber crop, is a potential substitute for wood to make composition boards. This work investigated single- and three-layer kenaf core particleboards (KPBs) and kenaf core-cedar wood composite particleboard (KCPB) with polymeric methylene diphenyl diisocyanate (pMDI) and phenol formaldehyde (PF) resins. The physical and mechanical properties including bending modulus (MOE) and strength (MOR), internal bond (IB) strength, water absorption (WA), thickness swelling (TS), and linear expansion (LE) were tested following the ASTM D 1037 and ANSI A 208.1 standards. It was shown that kenaf core can be made into standard-satisfying particleboards with comparable performances to cedar-based wood panels. Three processing factors, i.e., board density, resin content, and layered construction, had significant influences on panel properties. KPBs denser than 0.70 g/cm3 and with 6% PF met with the standard specifications. The WA, TS, and LE of single-layer KPBs decreased with increased density. Three-layer KPBs showed improved MOE, MOR, and IB strengths, and effectively avoided the unbalanced structure shown in the single-layer KPBs in thickness direction. The three-layer KPBs with a 50:50 surface-to-core ratio had the best comprehensive performances. The results can be helpful for the application of kenaf residues in the wood composites industry.

The process of wood drying can induce defects caused by drying stress, which limits the processing and utilization of this valuable material. Here, we investigated elastic strain, viscoelastic creep strain, and mechano-sorptive (MS) creep strain caused by shrinkage anisotropy using the image analytical method during slow conventional drying of white birch (Betula platyphylla Suk) disks. The rheological properties of wood disks with different moisture contents (MC) were analyzed together with the influences of MC and radial position on each strain. The results showed that relations between stress and strain are complex; below the fiber saturation point (FSP), the wood disk is initially subject to tangential tensile stress; with decreasing MC, the tensile stress turns into a compressive stress. MS creep strain increased with decreasing MC; however, elastic strain and viscoelastic creep strain were positively correlated with MC. Elastic strain decreased after first increasing, and then remained stable while the MS creep strain significantly increased from pith to bark, at 10% MC and 18% MC, respectively. Shrinkage anisotropy was the main reason for strain during the drying processing, and it was one of the main factors causing cracks during drying or application.

Oil palm mesocarp fibers (OPMFs) are left as a waste material after oil extraction. A new application of OPMF is needed to economically utilize these fibers; thus OPMFs need to be modified to render them hydrophobic. Hydrogen peroxide was used to initiate the graft copolymerization of butyl acrylate onto OPMF in aqueous solution. The duration of reaction, temperature, and amounts of butyl acrylate and initiator were optimized using response surface methodology (RSM) coupled with a four-factor central composite design (CCD). The response variable was percentage grafting (%G). A quadratic model was obtained and developed to correlate the independent variables to %G. The optimum conditions predicted through RSM were 110 min duration of reaction, 50 °C temperature, 28 mmol of monomer, and 5.99 mmol of initiator, with a %G of 116.2%. Synthesized graft copolymers were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis. The thermal stability of OPMF improved significantly after grafting. The FTIR and SEM results showed that graft copolymerization successfully occurred onto the OPMF backbone. The tensile test results support the utilization of grafted OPMF as a potential compatibilizer.