Volume 11 Issue 4

By exercising of one’s curiosity, in combination with a lot of persistence, it is possible to solve some seemingly intractable problems. Many readers of this journal will have spent much, if not all of their careers, in university laboratories. In such settings there is an understandable emphasis on understanding underlying reasons. In other words, one is expected to focus on “why things happen” rather than just getting results. But if such an approach works well at the university, how about applying it at the production facility? This editorial features the stories of a man who was brave enough to spend his career asking “why” questions while working to improve the operations of paper mills.

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.

This article presents a methodology based on genetic algorithms (GA) optimization with a three-dimensional numerical solution to the diffusion model obtained by using the finite volume method (FVM) for determining the effective moisture diffusivity in lumber. The objective or error function between measured and simulated drying curves was obtained, and the effective moisture diffusivity parameters with greatest correspondence between measured and estimated values were obtained. As a result, a new equation for effective moisture diffusivity was proposed, which depends on lumber moisture content and drying temperature. Effective moisture diffusivities ranged from 1.120 × 10-9 to 1.277 × 10-8 m2/s. Finally, the proposed coefficients were validated by experiments. The drying kinetics were successfully simulated with the optimized effective moisture diffusivity model.