Abstract

Application of microwave energy to wood can increase permeability in order to improve the impregnation of treatments, particularly important in refractory species such as eucalyptus. However, microwave treatment can also affect the physical and mechanical properties of wood. This paper discusses the application of microwave treatments of different intensities to improve impregnability (uptake and retention) and examines the effects on the mechanical properties of eucalyptus wood (Eucalyptus globulus). Microwave treatments significantly improve uptake and retention of the protective agent, especially in the most severe treatment. In contrast, there was a clear decrease in mechanical properties (modulus of elasticity and bending, compression, tension and shear strength) as a function on the energy applied. The effect of microwaves on the properties of wood varies depending on moisture content at the time of treatment.

Highlights

  • The objective of this paper was to study the application of different energies based on MW treatments to Eucalyptus globulus heartwood in order to improve permeability, while at the same time evaluating the influence on the mechanical properties

  • Four of the groups were conditioned to an approximate moisture content of 12%, while the moisture content of the other three groups remained above 30%

  • In dry samples (12% MC) the maximum moisture content loss was observed at the maximum MW energy, with an average value of 2,12%

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Summary

Introduction

The application of microwaves (MW) to wood has been widely studied (Oloyede and Groombridge 2000, Leiker and Aurich 2003, Hanson 2007, Torgovnikov and Vinden 2010) for drying (Antti 1999, Leiker and Adamska 2004, Resch 2006), increasing permeability (Mollekopf and Wagenfür 2002) or improving wood properties for pulping (Torgovnikov and Vinden 2009). Microwaves consist of electromagnetic energy at frequencies between 300MHz and 300GHz. MW energy absorption produces the random vibration of polarized molecules, leading to an increase in temperature. Pressure causes fractures and the creation of micro-holes in thinwalled cells, increasing the permeability of the wood

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