Experimental investigation on the influence of microwave technology on the treatability and mechanical properties of Portuguese southern blue gum wood

Abstract

Despite presenting global relevance and satisfactory mechanical properties for structural applications, the Portuguese eucalyptus, southern blue gum (Eucalyptus globulus Labill.), faces difficulties with impregnation with preservative products due to its limited permeability (treatability), which limits its utilization. Microwave (MW) treatment of wood offers a promising avenue for overcoming this issue, but it may impact the mechanical properties. It was identified that there remain research gaps regarding the impacts of MW treatment on eucalyptus. Hence, it was aimed to identify the optimum MW parameters for southern blue gum wood to enhance its impregnability without compromising the mechanical properties. This will contribute to meeting the growing demand for wood for construction. Small clear wood specimens containing heartwood were separated into three groups: two underwent MW treatment, and one did not (control). The samples were impregnated with a preservative product and after submitted to mechanical testing. The MW treatment significantly enhanced the retention of the preservative product, which is remarkable given the impossibility of impregnating eucalyptus heartwood using conventional pressure methods. Although there were slight decreases in the mechanical properties of the MW-treated specimens, they were statistically equivalent to the control group. New insights into the mechanical bending behavior of MW-treated samples also arose. The mechanical properties of MW-treated eucalyptus samples surpassed those of other globally used wood species. Thus, MW treatment presented itself as an effective process for increasing eucalyptus impregnability, and it has the potential to augment southern blue gum's use as a raw sawn and engineered structural wood material worldwide.