Research Articles

The aim of this study was to evaluate the effect of CNC routing, using different parameters with the Taguchi experimental design, on the surface quality of various wooden (pine, spruce, and beech) edge-glued panels (EGP). The study evaluated five processing parameters: cutting direction, cutting depth, cutting width, feed rate, and spindle rotation speed, and their effects on surface roughness on pine, spruce, and beech EGP. Based on the results of statistical analysis of the burr surface roughness values, the mentioned parameters affected panels at varying levels. It was seen that the parameters were only responsible for ~34% (Rz) of the roughness on the surface of pine EGP, ~49% (Rz) of spruce EGP, and ~27% (Rq) of beech EGP. Statistically important parameters were as follows: cutting direction for pine, cutting depth (tip diameter) and feed rate for spruce, and cutting direction and feed rate for beech.

Wet-white and wet-blue leather shavings were investigated as promising new raw materials as they seem to offer a high availability and cost competitiveness compared to wood, and they also show some interesting new properties. In order to determine a new field of application for the leather shavings and to understand the fiber particle interaction, boards with a density of 700 kg/m³ and a resin load of 12% were produced with varying contents of wood fibers, wet-blue and wet-white leather particles. These panel composites were characterized with regard to their internal bond, modulus of elasticity, and modulus of rupture. Furthermore, the micro-structure of selected panels was investigated by X-Ray computed tomography (CT). Different phases within the CT data were segmented using thresholding algorithms, and the pore size distribution of the panels was analyzed. A substantial difference was found between the panels produced due to the incorporation of leather particles. The internal bond strength increased with rising leather particle content, whereas other mechanical properties dropped. The CT analysis showed a huge difference in the pore size distribution and the number of pores for the different materials. This indicates that the differences visible in mechanical testing were induced by the different geometry of the constituents.

Five kinds of commercially available wood-based composites (softwood plywood, hardwood plywood, medium density fiberboard, oriented strand board, and particle board, hereinafter abbreviated as SWP, HWP, MDF, OSB, and PB, respectively) post-treated with alkaline copper quat (ACQ) and copper azole (CA) were exposed to decay and subterranean termite activity under protected above-ground conditions in a southern Japan field test site for three years. Variables examined included comparisons of untreated and treated wood-based composites, preservative type, and retention levels. Both biological attacks developed with time. Termite damage started earlier, and the severity of attack was higher than decay fungi. Untreated MDF and PB were highly resistant to field conditions during the 36 months. Untreated OSB, HWP, and SWP were the least resistant composite types. ACQ and CA treatments significantly improved the durability of the wood-based composites resulting in 64.4%, 47.9%, and 22.5% higher termite ratings when compared to their untreated controls for OSB, HWP, and SWP, respectively. Preservative types and increased retentions did not significantly affect the decay and termite ratings. These results suggest that ACQ and CA post-treatments at exterior protected and unprotected (K3) and double K3 retention levels significantly improved durability of wood-based composites tested but failed to provide full protection.

Co-firing ramie residue with coal was carried out in a thermogravimetric analyzer and a cyclone furnace to evaluate the effects of coal fraction (0 to 30 wt. %) on combustion performance. Thermogravimetric analysis (TGA) results showed that devolatilisation was the predominant process when the coal percentage in the blend was below 30 wt. %. For pure biomass firing in the cyclone furnace, an optimum equivalence ratio (ER =1.16) was found. Coal additions (0 to 30 wt. %) led to less slagging/fouling problems, higher combustion temperature and higher combustion efficiency along with low pollutant emissions, while the improvement in combustion temperature was weakened as the coal blend ratio exceeded 20 wt.%. The maximum temperature in the cyclone furnace increased from 1215 to 1319°C as the coal fraction increased from 0 to 30 wt.%.

Ultrasonic energy was applied to assist the wood vacuum drying process. At a drying temperature of 60°C, the absolute pressure was either 0.05 MPa or 0.08 MPa; the ultrasonic power and frequency were 100 W and 28 kHz, respectively. The results showed that the effective water diffusivity of the specimens dried by the ultrasonic assisted vacuum drying at 0.05 MPa or 0.08 MPa were higher than that of the samples dried without ultrasound. The ultrasound-vacuum drying rate was much faster than that of drying without ultrasound, especially for wood with a moisture content above the fiber saturation point. Drying at the absolute pressure of 0.05 MPa was faster than that of 0.08 MPa. Ultrasound-assisted drying was especially more beneficial when removing free water. The ultrasound-vacuum drying method could be applied in the wood drying industry as a means of saving energy and minimizing product quality damage.

This work focused on providing a molecular understanding of the way the polymeric properties of kraft lignin and its derivatives are affected by various thermal treatments. This information was then correlated with the polymeric properties of the materials (glass transition temperature (Tg), molecular weight characteristics, and thermal stability) for a series of selectively and progressively derivatized softwood kraft lignin samples. Softwood kraft lignin was highly susceptible to thermally induced reactions that caused its molecular characteristics to be severely altered with the concomitant formation of irreversible cross-linking. However, by fully methylating the phenolic OH groups from within the structure of softwood kraft lignin, the thermal stability of these materials was dramatically enhanced and their Tg reduced. While optimum thermal stability and melt re-cycling was observed with the fully methylated derivatives, fully oxypropylated phenolic substitution did not offer the same possibilities. The accumulated data is aimed at providing the foundations for a rational design of single component, lignin-based thermoplastic materials with reproducible polymeric properties when thermally processed in a number of manufacturing cycles.

Chemo-enzymatic functionalization offers an innovative approach to produce paper and board products with enhanced performance. Unbleached softwood kraft pulps were functionalized by laccase with methyl syringate(MS), p-hydroxybenzoic acid(HBA), gallic acid(GA), and syringaldehyde(SyA). The wet strength of fibers treated with MS and SyA increased by 57.9% and 31.9%, respectively. The dry strength of fibers treated with HBA, GA, and SyA increased from about 64 N·m/g to 68 N·m/g. The opacity of MS-treated fibers was the highest, and the surface lignin coverage increased. The kappa number and surface lignin of HBA-treated fibers changed little; however, the total carboxyl group significantly increased. The participation of phenolic compounds enhanced the reactivity of fibers to laccase in varying degree. However, the reactivity of phenols to laccase did not show a direct relation to the paper strength. All treatments with phenols decreased the brightness and the curl index of fibers. The syringyl-type phenols with hydrophobic groups (OCH3) were shown to be effective for improving the pulp wet strength. The compounds with carboxyl groups enhanced the pulp dry-strength. The observed pulp strength improvement could be attributed to the formation of covalent bonding via radical coupling, the attachment of the functional group, increased bonding area, and fiber entanglement.

Heat treatment under controlled temperatures can help enhance bamboo’s durability and dimensional stability. The treatment may simultaneously affect thermal and mechanical performance of bamboo fibers (BFs). The aim of this work was to study the effect of heat treating temperature on thermal decomposition kinetic properties of heat-treated BFs and resulting polymer composites using dynamic thermo-gravimetric analysis under nitrogen. Degradation models including the Kissinger and the Flynn-Wall-Ozawa methods were used to determine the apparent activation energy (Ea) of various materials. The results indicated that the thermal decomposition of the heat-treated BFs mainly occurred within a temperature range between 245°C and 354°C. The values of Ea varied from 161 to 177 kJ/mol and increased with increased heat treating temperatures for the fibers. The thermal decomposition of the heat-treated BF and high density polyethylene blends mainly occurred within a temperature range of 307°C and 483°C. The values of Ea were between 225 and 236 kJ/mol and decreased with the increase of fiber heat-treating temperatures. The established thermal decomposition kinetic parameters can help aid the development of polymer composites from heat-treated bamboo materials.

The effect of zinc borate (ZB) treatment on the mechanical and morphological properties of wood flour/polypropylene composites was investigated. Wood flour was first treated with ZB solution (1% w/w in ethanol-distilled water), followed by 24 hours of soaking on an unheated magnetic stirrer hot plate until relatively complete saturation was reached. Then, composites based on ZB-pretreated, ZB-treated-during-manufacturing, and untreated wood flour, polypropylene and coupling agent were made by melt compounding and then injection molding. The ZB treatment had no significant influence on mechanical properties of the composite with the exception of tensile strength. The composite made with ZB-pretreated wood flour exhibited the same mechanical properties as the composites made with ZB-in-process-treated wood flour; however there were statistically significant differences between flexural modulus and tensile strength of ZB-pretreated composites and ZB-in-process treated ones. Specimens containing the ZB showed lower flexural, tensile, and impact strength compared with the untreated specimens. However, the zinc borate treatments produced modest improvements in hardness performance. The SEM micrographs revealed that the outer surface of the wood fibers was coated by some crystalline deposits of zinc borate.

The objective of this study was to investigate the deformation behavior and damage model of bamboo bundle corrugated laminated composites under low velocity impact loading. The influence of different stacking sequences, i.e., bamboo bundle parallel to the corrugated waves (type I), cross-ply (type II), and perpendicular to the waves (type III), in laminates was studied in regard to impact loading. A shape parameter, K, was developed to quantify the effect of corrugation on impact response. The results of this study indicated that the type I composites displayed the optimum impact performance, followed by types II and III. The total energy absorbed by the type I laminates was 1.3 and 2.2 times as much as types II and III . The values of peak load were type I > type II > type III. The composites deformed and failed in different manners under low velocity impact loading: material failure, delamination and fiber tensile fracture, and structural collapse were the main modes of failure for type I, II, and III, respectively. The effect of the corrugated shape on impact properties of composites was positive for type I, but negative for type II composites.