Research Articles

The aims of this study were to introduce a new laboratory microwave device developed for the modification of wood properties and to examine the effect of microwave radiation on moisture loss, surface temperature, and mechanical properties (the static modulus of elasticity – MOE, and the modulus of rupture – MOR) of Norway spruce (Picea abies). The device was developed for a continuous modification process. The microwave (MW) generator works at a frequency of 2450 MHz, and the adjusted output ranges from 0.6 to 6 kW. The experiment was based on four different modes of MW modification, each of them with a varied generator output and conveyor speed. Regarding mechanical properties, the results showed that a feasible output for the MW modification of the samples was up to 3 kW, with a conveyor speed of around 0.4 m/min. The greatest moisture loss, approximately 40%, was found in the group treated at 5 kW and 0.2 m/min. The highest surface temperature, 87 °C, was measured in the group treated at 5 kW and 0.4 m/min after the second passage through the modification chamber.

Copper-based compounds are some of the most important biocides for the protection of wood in heavy duty applications. In the past, copper was combined with chromium compounds to reduce copper leaching, but a recent generation of copper-based preservatives uses ethanolamine as a fixative. To elucidate the leaching of copper biocides from wood, Norway spruce (Picea abies) wood was treated with a commercial copper-ethanolamine solution with two different copper concentrations (cCu = 0.125% and 0.25%). The aim of this research was to compare the laboratory leaching standards (ENV 1250-2, CEN/TS 15119-1, and CEN/TS 15119-2) with the field leaching studies in ground and above ground. The results indicated that the first leaching peak appears in the initial phases of leaching, both in laboratory and field studies. The degree of copper leaching is also affected by the method of treatment; copper-ethanolamine preservative solutions, when applied with superficial treatments, are more prone to leaching than is vacuum-pressure treated wood. On average, between 25% and 36% of copper was leached from the impregnated wood after 42 months of exposure.

The reaction kinetics of gasification are important for the design of gasifiers using biomass feedstocks, such as lignin, produced in biorefinery processes. Condensed and uncondensed lignin samples used in the present study were prepared using the SEW (SO2-ethanol-water) fractionation process applied to spruce wood chips: the dissolved lignin is precipitated during the recovery of SO2 and ethanol from the spent fractionation liquor. The gasification of char made from condensed and uncondensed SEW lignin was investigated using thermogravimetric analysis (TGA) at atmospheric pressure using either CO2 or steam. The main aim of this study was to quantify the reaction rate during the gasification process, which was found to be best described as zero-order. All experiments were performed at constant temperatures between 700 and 1050 °C to obtain the necessary information for describing the reaction rate equation in an Arrhenius form; the heating rate was 20 °C/min for both samples. The experiments led to almost similar results for both samples. The activation energies of CO2 gasification were approximately 160 kJ/mol and 170 kJ/mol for uncondensed and condensed lignin char, respectively. The activation energies of steam gasification were approximately 90 kJ/mol and 100 kJ/mol for uncondensed and condensed lignin char, respectively.

The pressure and temperature at the same location in the middle cross section of Sugi wood were measured simultaneously during radio-frequency/vacuum (RF/V) drying. The distribution and variation of pressure and temperature in the wood cross section were investigated in different drying stages. The pressure behavior during the drying process was due to the pressure reduction rate and water vapor generation rate in wood. The temperature was higher in the center and was low from the center to surface layer. Pressure and temperature did not present symmetrical distributions along the vertical direction in the cross section. The pressure was irregular during the timber heating stage and became higher in the central zones than in the intermediate and surface layer zones during the drying process. Pressure curves exhibited three stages (irregular, rapid decreasing, and slow decreasing), in combination with an initial heating stage and a constant temperature stage. Above the fiber saturation point (FSP), the pressure (P) was greater than or equal to the saturated vapor pressure (Ps), corresponding to the temperature at the same location; below the FSP the pressure was maintained by superheated vapor and was smaller than Ps.

H2O2 is both bactericidal and the main oxidant responsible for lignin degradation reaction catalyzed by manganese peroxidase (MnP) and lignin peroxidase (LiP). Thus, H2O2 treatment of corn stalk and the implementation of solid-substrate fermentation (SSF) is possible to increase the removal rate of lignin from stalk in the process of SSF and after SSF, while avoiding the need to sterilize the raw materials. To demonstrate this approach, SSF was initially carried out using corn stalk pretreated with different concentrations of H2O2 as a substrate. A. oryzae was found to grow well in the 3% H2O2-pretreated corn stalk. H2O2-pretreated corn stalk showed increased MnP and LiP synthesis and disintegration of lignin, but inhibited cellulase synthesis and cellulose degradation. Production of the SSF (200 g) on the 10th day was hydrolyzed in the presence of additional 600 mL different concentration of H2O2 aqueous solution. The total removal of lignin (73.15%) of hydrolysis for 10 h at 3% H2O2 solution was highest and far higher than that at the 12th day, as achieved by conventional SSF. Applying this strategy in practice may shorten the time of lignin degradation, increase the removal of lignin, and decrease the loss of cellulose. Thus, this study has provided a foundation for further study saccharification of corn stalk.

The surface free energy and dynamic wettability of wood are important to the performance of its adhesive bonding strength. In this work, the surface free energy of poplar wood samples machined with different processes were calculated by the OWRK (geometric mean) and vOCG (acid-base) methods, and the dynamic wettability of adhesives on wood samples was studied using the S-D wetting model. The results indicate that the contact angles of reference liquids on rotary wood samples were greater than those on planed or sawn wood, and the rotary wood samples were more hydrophobic. The effect of surface roughness on contact angle was insignificant compared with surface structure morphology. The total surface free energy was almost the same for the planed and sawn wood, as calculated by the OWRK and vOCG methods, and the surface free energy of rotary wood samples was lower than that of planed or sawn wood samples. The initial and equilibrium contact angle increased as the viscosity of adhesive increased for all the wood samples, and the contact angles of rotary wood samples were greater than those of planed or sawn wood; however, the K-value was lower. The wettability of the loose side was higher than that of the tight side. Contact angles decreased when surface free energy increased, while the K-value increased.

Ammonium polyphosphate (APP) was synthesized by heating a mixture of phosphoric acid and urea, and APP/diatomite composite flame-retardant fillers were prepared by two methods: mixing and in situ polymerization. Flame-retardant paper was made by adding the prepared composite fillers to paper. The APP and APP/diatomite composite fillers were characterized by XRD, 31PNMR, SEM, FTIR, and TG. The flame retardation of paper containing these composite fillers was determined. Results showed that the prepared APP had a minimum solubility when the molar ratio of phosphoric acid to urea was 1:1.8. Under these conditions, its degree of polymerization was 91.21. After mixing and in situ polymerization, a large amount of APP was adsorbed into the surface of the diatomite. These two APP/diatomite composite fillers had similar thermal stabilities, butthe flame retardation of paper containing in situ polymerized composite filler was better than that of paper containing the composite filler obtained by mixing.

In this study, four engineered proteins containing two family 1 and/or family 3 carbohydrate binding modules (CBMs) were constructed and expressed as soluble forms in Escherichia coli. Their binding performances and effect on paper’s mechanical properties were comprehensively studied with the aim to design suitably engineered CBMs as novel biomaterials for use in the production of new cellulose materials. The recombinant engineered double CBMs exhibited obvious differences in their adsorption to different cellulosic substrates. The CBM3-GS-CBM3 was the most effective in enhancing paper mechanical properties in terms of folding endurance (27.4%) and tensile strength (15.5%) among the four engineered double CBMs, but it gave rise to only a slight increase in bursting strength (3.1%). On the other hand, CBM1-NL-CBM1 achieved a significant simultaneous increase in tensile strength (12.6%) and burst strength (8.8%), as well as folding endurance (16.7%). Unexpectedly, CBM3-GS-CBM1 and CBM3-NL-CBM1 had the lowest effective paper property improvement. The differences in types of CBMs and linker peptides in engineered double CBMs may contribute to the considerable differences in their cellulose binding and paper property modification. Our data suggested that CBM1-NL-CBM1 may provide a better upgrade of the secondary pulp, which makes it very suitable for fiber recycling. Meanwhile, CBM3-GS-CBM3 may have particular potential for paper manufacture requiring high folding endurance.

Two field trials were conducted with untreated coconut wood (“cocowood”) of varying densities against the subterranean termites Coptotermes acinaciformis (Froggatt) and Mastotermes darwiniensis Froggatt in northern Queensland, Australia. Both trials ran for 16 weeks during the summer months. Cocowood densities ranged from 256 kg/m3 to 1003 kg/m3, and the test specimens were equally divided between the two termite trial sites. Termite pressure was high at both sites where mean mass losses in the Scots pine sapwood feeder specimens were: 100% for C. acinaciformis and 74.7% for M. darwiniensis. Termite species and cocowood density effects were significant. Container and position effects were not significant. Mastotermes darwiniensis fed more on the cocowood than did C. acinaciformis despite consuming less of the Scots pine than did C. acinaciformis. Overall the susceptibility of cocowood to C. acinaciformis and M. darwiniensis decreases with increasing density, but all densities (apart from a few at the high end of the density range) could be considered susceptible, particularly to M. darwiniensis. Some deviations from this general trend are discussed as well as implications for the utilisation of cocowood as a building resource.

The present research is focused on the manufacturing and analysis of the thermal and electrical properties of advanced ceramics from alumina (Al2O3) with carbon nanofiller (CNF) from oil palm ash (OPA). The oil palm ash was used to produce carbon black nanofillers with a size of 50 to 100 nm via a ball milling process after undergoing pyrolysis in a furnace at 1000 °C. CNFs were added to the alumina at varying weight fractions and sintered at 1400 °C for the production of CNF ceramic composites. The coefficient of thermal expansion (CTE), electrical conductivity (EC), and electrostatic discharge (ESD) of the ceramic composites were measured. The CTE did not increase with increasing CNF weight and behaved like an alumina matrix. The EC (I-V) showed positive results with increasing CNF weight. The ESD measurement gave predictable results on the dissipative characteristics of ceramic composites due to the insulating nature of alumina with the addition of CNF. Thus, the addition of OPA to alumina may present a suitable route for improving the electrical properties of advanced ceramics.