Research Articles

This study investigated the effects of densification and heat post-treatment on the Janka hardness and microscopic structure of relatively low-density Uludağ fir, linden, and black poplar woods. Wood samples were densified with compression ratios of 25% and 50% at 100 °C and 140 °C, respectively. Heat post-treatment was then applied to the samples at     185 °C and 212 °C for 2 h. The hardness in the radial and tangential directions was determined, and morphological changes in the cell structures were analyzed using scanning electron microscopy (SEM). The hardness values in the radial and tangential directions of the densified samples increased depending on the compression rate and treatment temperature. The hardness values in both directions were higher in the 50% compressed samples. For samples compressed at 140 °C, the hardness values were higher in the tangential direction, whereas the samples compressed at 100 °C were higher in the radial direction. After the heat post-treatment process, the hardness values of all samples decreased. As the treatment temperature increased, more adverse effects on the hardness was noted. According to the SEM analyses, the densification and heat post-treatment deteriorated the cell structure of the samples. The more cell deformation was observed in the samples densified at 100 °C with compression ratio 50% and high heat post-treatment temperature.

To obtain a suitable refining process for Pinus massoniana cellulose fibers (PMCF) and China fir cellulose fibers (CFCF), the effects of the beating gap and the pulp consistency on the physical properties and the morphology of the two cellulose fibers were investigated. The results showed that the physical properties of the PMCF and the CFCF were well affected by the beating gap and the pulp consistency. The CFCF showed a smaller weight-average length and width than that of the PMCF. The CFCF exhibited smaller weight-average length, width, and kink index than the PMCF. It is easy to get the high beating degree, indicating it is more easily to be refined. Additionally, the tensile index and burst index of PMCFP and CFCFP increased with increasing beating degree, while the tear index decreased. Compared to the CFCF, the paper made from PMCF had superior strength properties. Consequently, the PMCF was suitable for refining with a high pulp consistency and a medium beating gap, whereas the CFCF had a medium pulp consistency and a big beating gap.

Oil palm empty fruit bunch (OPEFB) was pretreated by NaOH-steam explosion and then fermented to ethanol by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes usingKluyveromyces marxianus G2-16-1 at 40 ºC. The maximum ethanol production by the SHF and SSF processes was 8.09 g/L (22.21 g/L reducing sugar, 0.08 g/g OPEFB) and 13.658 g/L (0.136 g/g OPEFB), respectively, at 48 h. The OPEFB hydrolysate mixed with molasses to 22% (w/v, total sugar) gave an ethanol yield of 61.60 g/L (0.38 g/g total sugar) at 72 h, while molasses alone gave 53.89 g/L (0.34 g/g total sugar). The OPEFB slurry (OPEFBS; OPEFB hydrolysate containing the solid residue of pretreated OPEFB) gave a maximum ethanol yield of 68.77 g/L (0.44 g/g total sugar) when it was mixed with molasses. Scanning electron micrographs of the solid OPEFB residue in the OPEFBS showed yeast cells adsorbed to the OPEFB fibers. The results indicated that ethanol production from molasses mixed with OPEFB hydrolysate was equal to the cumulative sum of ethanol production from each raw material, and the solid OPEFB residue in the OPEFBS increased the ethanol production in the co-fermentation of molasses and OPEFB hydrolysate.

The bond performance and bonding mechanism were evaluated for a Konjac glucomannan (KGM), Chitosan (CS), and polyvinyl alcohol (PVOH) blended wood adhesive. An optimized experimental strategy was used to investigate the effects of the formula parameters of adhesives on the bonding strength of plywood using a Box-Behnken design and response surface methodology (RSM). The microstructure of the blended adhesives was analyzed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). An optimum bonding strength (3.42 ± 0.31 MPa) was achieved with concentrations of KGM, CS, and 10% PVOH of 2.3%, 2.3%, and 5.0%, respectively. There was strong hydrogen bonding between the KGM, CS, and 10% PVOH adhesives and the interface. SEM observations indicated that the blended adhesive exhibited a net-like structure that increased the overall bonding strength. These results provided the scientific basis for the continual development of environmentally friendly wood adhesives and the improvement of processing conditions.

An extensional flow mixture (EFM) system was studied, with the goal of achieving better distributive and dispersive mixing. The effects of different mixing strategies (masterbatch method (MB), polyethylene-grafted maleic anhydride (PE-g-MA) as a compatibilizer, and compounding devices, such as a single screw extruder (SSE), a twin screw extruder (TSE), and an extensional flow mixer (EFM)) on the mechanical, thermal, rheological, and morphological properties of ultrafine cellulose (UFC)-filled high-density polyethylene (HDPE) composites were investigated. Maximum tensile strength (17.7 MPa), tensile modulus (0.88 GPa), flexural strength (18.8 MPa), and flexural modulus (0.63 GPa) were obtained from the MB compounding method. The maximum stress-strain (13.8%) was obtained with EFM compounding. Polymer composites from SSE and SSE/EFM compounding methods with PE-g-MA exhibited slightly higher crystallinity compared with other compounding methods. The storage modulus of the samples prepared with the MB method was higher than those prepared with the SSE compounding method. The UFC-filled HDPE composites from the EFM compounding process exhibited lower melt viscosities than the other composites at high shear rates. Scanning electron microscopy (SEM) images showed the cellulose to be distributed and dispersed reasonably well in the HDPE matrix when using a coupling agent in combination with the MB and EFM compounding methods.

Glued-in rods have successfully been used for connections or reinforcement of timber structures due to their high strength and stiffness. However, their performance is potentially sensitive to temperature. This paper deals with an experimental investigation of the connections and adhesives in elevated temperatures. First, dynamic mechanical analysis (DMA) tests were performed to characterize an epoxy (EPX) and a polyurethane (PUR) adhesive. The evolution of the stiffness and the glass transition temperature, Tg, were measured in the range of 30 °C to 120 °C. Then, a total of 66 specimens with glued-in rods and the same adhesives were tested under a static tensile load at 20 °C, 40 °C, 50 °C, 60 °C, and 70 °C. In both types of tests, the EPX outperformed PUR due to its higher stiffness at temperatures of up to 40 °C; however, it showed a more rapid degradation of the stiffness and strength than the PUR at higher temperatures. No direct correlation was established between the Tg and the performance of the connections. The test results suggest that timber structures with glued-in rods may be vulnerable in service at temperatures above 40 °C.

A new processing technology using a nanosecond pulse laser to process micro-nano wood fiber is proposed in this paper. A test bench was designed and manufactured for the technology. The digital design process, experimental methods, and general layout principle of the test bench are introduced. When the factors that affected the results of the experiment were analyzed, it was found that cutting width and cutting depth were affected by cutting direction, cutting speed, and cutting power. The wood underwent thermal degradation near the point of processing. The results of the experiment showed that the technology is feasible.