Finger-jointing of green Eucalyptus globulus L. wood with one-component polyurethane adhesives

The use of glued finger joint in green wood, directly from the sawing process, would open the possibility to obtain glued timber from small-sized wood, achieving an efficient use of the original raw material. The gluing of finger-jointed green wood, with moisture content above the fibre saturation point, may improve the efficiency and the manufacturing process of glulam or joinery. This may be especially beneficial for a hardwood such as Eucalyptus globulus L., which is a globally important forest resource, but is a challenging wood to dry. This article presents a study on the possibility to develop finger joints with wood in green state. To compare them, conventional finger joints on dry wood and solid boards without end joints were also manufactured. Cold-setting and fast-curing commercial one-component polyurethane adhesive systems were used. Finger-jointed samples were tested to determine mean and characteristic values (5th percentile) of density, bending strength and modulus of elasticity, and the results were analysed and discussed. Green-glued joints showed no statistically significant differences compared to the solid boards and improved strength properties with respect to dry-glued joints.

Controlling the Thermal Stability of Kyanite-Based Refractory Geopolymers

The present project investigated the thermal stability of cold-setting refractory composites under high-temperature cycles. The proposed route dealt with the feasibility of using fillers with different particle sizes and studying their influence on the thermo-mechanical properties of refractory geopolymer composites. The volumetric shrinkage was studied with respect to particle sizes of fillers (80, 200 and 500 µm), treatment temperature (1050–1250 °C) and amount of fillers (70–85 wt.%). The results, combined with thermal analysis, indicated the efficiency of refractory-based kyanite aggregates for enhancing thermo-mechanical properties. At low temperatures, larger amounts of kyanite aggregates promoted mechanical strength development. Flexural strengths of 45, 42 and 40 MPa were obtained for geopolymer samples, respectively, at 1200 °C, made with filler particles sieved at 80, 200 and 500 µm. In addition, a sintering temperature equal to 1200 °C appeared beneficial for the promotion of densification as well as bonding between kyanite aggregates and the matrix, contributing to the reinforcement of the refractory geopolymer composites without any sign of vitrification. From the obtained properties of thermal stability, good densification and high strength, kyanite aggregates are efficient and promising candidates for the production of environmentally friendly, castable refractory composites.

Improvement of Binderless Banana Pseudo-Stem Particleboard Properties via Natural Laminating Materials

In this study, the first objective was to investigate the basic mechanical and physical properties of the binderless banana pseudo-stem particleboard (BBP) at a targeted density of 650 kg/m3. The second objective was to examine the effect of laminates on the properties of BBP. Three types of BBP were produced, that were oil palm veneer laminated BBP, layered banana leaf laminated BBP, and BBP without lamination. No adhesive was used in the production of the BBP, but for lamination process, cold setting polyvinyl acetate (PVAc) was used. Three tests were conducted which were internal bonding (IB), static bending, and water absorption resistance tests. According to the results, BBP without lamination had the lowest IB. The lowest modulus of rupture (MOR) and lowest modulus of elasticity (MOE) in static bending was also recorded by BBP without lamination. The highest IB, MOR and MOE, were of BBP laminated with oil palm veneer. These values were followed by IB, MOR and MOE of BBP with banana leaf lamination. Highest percentage water absorption (WA) was exhibited by BBP without lamination, followed by BBP laminated with oil palm veneer, and then by BBP laminated with layered banana leaves. The types of BBP significantly influence the MOR and MOE, but did not significantly affect the IB and WA. In general, laminating the BBP using natural layered materials has significantly improved the MOR and MOE.