Fast-grown wood generally contains a high proportion of juvenile wood that results in inferior dimensional stability and durability against biological deteriorations. In the present research, the Acacia mangium wood from plantation forests in Vietnam was treated with high temperature in air. The effects of heat treatment on physical properties of Acacia mangium wood, including mass loss (ML), water absorption (WA), water-repellent effectiveness (WRE) and anti-swelling efficiency (ASE) were examined. The results showed that the dimensional stability and the water-repellent effectiveness are increased by about 15-46% and 8-18%, respectively. However, the mass and dimension of wood are decreased. The results also indicated that both treatment temperature and treatment duration significantly affect the wood properties of Acacia mangium. It is thus concluded that heat treatment demonstrates an interesting potential to improve the wood quality of Acacia mangium for solid timber products. This technology provides an environmentally safe method of protecting sustainable common woods to give a new generation of value-added biomaterials with increased stability without the use of toxic chemicals.
This study evaluated the combined effects of rosin and aluminum sulfate (alum) on the leachability of boron, the color stability, and the decay resistance of poplar (Populus ussuriensis) wood treated with boron compounds. After leaching, the boron content in the leachates was analyzed via the azomethine-H method. Results showed the amount of boron released from the rosin-alum-boron solution treated samples was reduced by approximately 30% when compared to the samples treated with boric acid alone. All samples treated with rosin-alum-boron formulations exhibited greater color stability than that of the untreated controls after being exposed to natural weathering. The decay resistance of the treated wood blocks was measured via a soil-block culture. The results revealed that after being treated with the rosin-alum-boron formulations, the decay resistance of the leached wood was markedly improved. The average weight loss of the samples degraded by both fungi tested was less than 20%. Notably, scanning electron microscopy equipped with an energy dispersive X-ray analysis showed that the B element was still in the cell lumens of the leached and decayed wood blocks. This signified that the use of rosin combined with aluminum sulfate as a fixative agent may reduce boron leachability and could increase the usage of wood treated with boron preservatives.
This study examined the effects of rice straw steaming time and mixing ratio between rice straw and wood particle on the properties of mixed particle board from Acacia mangium Willd wood and rice straw. Rice straw and Acacia mangium Willd wood were collected in Hanoi, Vietnam. The particle board was three-layer particle board with the structural ratio of 1:3:1. The thickness, density and board size of the particle board were 18 mm, 0.7 g/cm 3 , and 800x800x18 (mm, including trimming), respectively. A resin mixture between commercial Urea-formaldehyde (U-F) adhesive and methylene diphenyl isocyanate (MDI) adhesive was used with a dosage of 12% for the core layer and 14% for the surface layer. In this experimental design, the steaming time for rice straw was 15, 30, 45, 60, and 75 minutes at 100 o C. The rice straw-wood mixing ratio was 10, 20, 30, 40, and 50%. The results showed that both mixing ratio and steaming time affect the properties of the particleboard, but the mixing ratio has a stronger impact. A higher mixing ratio and a longer steaming time resulted in a better quality of particleboard. The optimal steaming time for rice straw was 46.12 minutes with the straw-wood mixing ratio of 29.85% with the following characteristics of the particle board: the modulus of rupture (MOR) of 14.64 MPa, internal bond strength (IB) of 0.382 MPa, thickness swelling (TS) of 8.83%, and board density of 0.7-0.73 g/cm 3 .
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