Research Articles

Low mole ratio urea-melamine-formaldehyde (UMF) resins synthesized with 2.5% and 5.0% melamine levels added at the beginning, middle, and end points of the first alkaline step of the typical urea-formaldehyde (UF) resin synthesis procedure were compared with typical UMF resins synthesized with melamine additions made at the final alkaline step. Various resin analysis, particleboard preparation, physical performance, and formaldehyde emission level tests were carried out. UMF resins synthesized with melamine additions at the beginning of the first alkaline step showed adequate storage lives of 2 to 3 weeks, and their particleboard bonding tests showed small but significant improvements in water soak test values, while formaldehyde content values were slightly higher in comparison with typical UMF resins. The particleboards showed adequate board strength and the formaldehyde contents were relatively low to qualify for the E1 Class of European Standards. UMF resins synthesized with melamine addition made at the middle and end of the first alkaline step were highly turbid and showed chemical structure differences and very short storage lives and the resin synthesis procedures were concluded to be of little practical value.

Japanese pine sawyer beetle, pine shoot beetle, and Formosan subterranean termite were selected to investigate the inhibitory abilities of solid wood and wood-based composites (MDF and WPCs) made with Eucalyptus urograndis and Melaleuca leucadendra. The chemical components in the extractives of the two types of wood were also analyzed by GC-MS. The results indicated that the inhibitory ability can generally be listed in descending order as WPCs, MDF, and solid wood when made by the same wood filler. However, samples in each group made using Melaleuca leucadendra exhibited a higher inhibitory level than samples made using Eucalyptus urograndis. 2,3-dihydro-2,2-dimethyl-3,7-benzofurandiol, which was identified in the extractives of both woods (14.169% in Eucalyptus urograndis and 12.686% in Melaleuca leucadendra), was a significant factor for inhibition due to its high toxicity to insects. The chemical components with greatest potential for inhibition were stigmast-4-en-3-one (8.656%) in Eucalyptus urograndis andboth 3-demethyl-colchicine (2.642%) and squalene (1.649%) in Melaleuca leucadendra. Additionally, perlite-based MDF showed the best inhibitory ability, possibly because the alimentary of the insects are prone to injury by perlite. PVC-based WPCs had a greater inhibitory level than HDPE-based WPCs due to the presence of the Cl element in PVC, as well as the addition of calcium zinc stabilizer and inorganic filler.

The catalytic conversion of lignocellulosic biomass to levulinic acid in ionic liquid, [EMIM][Cl] was conducted using a hybrid catalyst. The hybrid catalyst (1:1 ratio) with equal CrCl3 and HY zeolite weight ratios was synthesized using a wet impregnation method. Initially, optimization of cellulose as a model compound was carried out using two-level full factorial design (23) with two centre points. Under optimum process conditions, 46.0% of levulinic acid yield was produced from cellulose. Subsequently, utilization of lignocellulosic biomass demonstrated 15.5% and 15.0% of levulinic acid yield from empty fruit bunch (EFB) and kenaf, respectively, at the optimum conditions. Meanwhile, in the presence of ionic liquid under the same process conditions, 20.0% and 17.0% of levulinic acid were obtained for EFB and kenaf, respectively. The results indicated that ionic liquid could disrupt the covalent linkages between the biomass structures and dissolved the hollocellulose. This allowed the hollocellulose chains, accessible to the chemical transformation, to react and produce levulinic acid in presence of the hybrid catalyst. This study demonstrated that the combination of hybrid catalyst and ionic liquid has the potential to be applied for biomass conversion to levulinic acid under adequate process conditions.

To achieve a desired ethanol concentration and maximize substrate concentration, the fed-batch simultaneous saccharification and fermentation (SSF) process was performed on steam-exploded corn stover using the yeast strain Saccharomyces cerevisiae Y5. The fed-batch SSF experiments were conducted with feed loading and scheduled feed time conditions that were optimized with response surface methodology (RSM). The overall ethanol yield (based on the raw material cellulose content) in 48 h was as high as 64.0%, which was achieved with a final substrate loading of 26%(w/w), enzyme loading of 7 FPU/g cellulose, and dry yeast loading weight of 2.0 g/L. No additional yeast cells or enzymes were added during solid substrate fermentation.

In Central Europe the main species that are used for the production of sawn wood are spruce, pine, and European beech. After the sawing process, the sawn timber is technically dried to a certain moisture content by means of condensation drying. The water movement in the cellular structure, which is caused by the drying process, draws some of the extractives into solution. In the process of kiln drying, hot air evaporates the water and the dissolved extractives. Some of the water condenses on the floor and the walls of the kiln, while the rest is blown out with the steam. Therefore, condensate was taken from the bottom of the kiln as well as from the energy recovery system. A chemical analysis by means of purge-and-trap showed the presence of volatiles that could be classified as typical for the wood materials from which they originated under the conditions of high temperature and high moisture content.

Unbleached kraft pulp fibers were modified with laccase and ferulic acid (FRC) to improve their physical strength properties in paper products. The optimal conditions of laccase-FRC modification were examined in terms of the physical properties of pulps. The effects of laccase-FRC modification on the carboxyl group content and surface lignin content of pulps were investigated. The surface morphologies of laccase-FRC-modified pulp fibers were observed by atomic force microscopy (AFM). The carboxyl group and surface lignin contents for laccase-FRC-modified pulps increased compared to the control pulp. AFM phase images showed that the laccase-FRC-modified fiber surfaces were covered with large granular substances from the products of FRC grafting and lignin polymerization/condensation reactions. The observed

Three tannin-based foam formulations differing in the type of surfactant added were tested during foaming via simultaneous monitoring of the variation in temperature, foam rising rate, internal foam pressure, and dielectric polarization, the latter being a direct measure of the setting and curing of a thermosetting foam. This monitoring is an effective descriptor of the process and possible characteristics of the foam being prepared and constitutes an invaluable tool for foam formulation. The addition of a surfactant was shown to have a major effect on foam dynamics by retarding the onset of cross-linking to a lesser or greater extent in relation to the peak of maximum temperature in self-blowing foams. Cationic surfactants, or non-ionic surfactants capable of transforming into cationic species under the acidic environmental conditions used for tannin-based foams, were found to retard cross-linking more markedly than did non-ionic surfactants.

Binary bio-composites of acorn shell (AS) and low density polyethylene (LDPE) were prepared via a twin-screw extruding method. The mechanical properties of the composites decreased with increasing AS content, and all composites maintained similar tensile strength as expected based on the Nicolais-Narkis model, indicating weak adhesion between AS and LDPE. The effects of three compatibilizers, ethylene-acrylic acid (EAA), ethylene-vinyl acetate (EVA), and maleic anhydride grafted polyethylene (PE-g-MAH) on the composites were also studied. The results showed that the three compatibilizers improved the mechanical properties of composites at different levels, and the PE-g-MAH compatibilizing system showed the best mechanical strength, which was increased by about 80% from that of the control. Micro-morphologic investigation revealed a rough fractured surface, indicating that the addition of compatibilizers improved the interfacial bonding properties of the matrix materials LDPE matrix. Dynamic mechanical thermal analysis (DMA) further confirmed that the addition of compatibilizers significantly improved the compatibility of blending components and changed the properties of LDPE matrix materials.

Green composites are gradually replacing general plastics to achieve the aim of environment sustainability. In the present study, both compatibilized and uncompatibilized recycled polypropylene (RPP) and peanut shell powder (PSP) composites were prepared. The effect of various PSP loadings (0 to 40% by weight) on the processing, tensile properties, morphology, Fourier transform infrared (FTIR) analysis, and water uptake properties were examined. The results showed that the incorporation of PSP caused an increase in stabilization torque, tensile modulus, and water absorption, but lowered the tensile strength and elongation at break of the RPP/PSP composites. Compatibilized RPP/PSP composites with poly(ethylene-co-acrylic acid) (PEAA) significantly enhanced the tensile properties while decreasing the water absorption of RPP/PSP composites. FTIR analysis revealed a slight change in band positions and intensities, indicating a distinct interaction between the chains of polymers. SEM micrographs showed the interaction between PSP and the matrix.

In this study, old corrugated container (OCC) pulp was added in different ratios (5%, 10%, 15%, 20%, and 25% w/w) to unbleached virgin pulps of both European black pine and Scots pine, and its effects on paper properties were investigated. As a control, OCC pulp-free handsheets were separately produced from European black pine and Scots pine pulps. The results indicated that the addition of OCC pulp decreased the strength properties, except for the tear index, of the handsheets. In addition, compared to the control handsheets, the paper containing the OCC pulp displayed higher air permeability. The results showed that up to 10% of the virgin softwood kraft pulp could be replaced with OCC pulp without bringing about considerable loss of strength. Also, this ratio of OCC addition could be suitable for production of wrapping papers.