Dielectric properties of selected wood species in Poland
The dielectric properties of seven wood species from Poland were measured as a function of frequency and grain orientation of wood. Measurements were conducted parallel and perpendicular with respect to the visible grain for specimen cut from sapwood and heartwood, at frequencies ranging from 1 kHz to 1 MHz. Both, relative permittivity and loss coefficient were affected by frequency and anisotropic direction. The most significant influence of wood species on dielectric wood properties was observed below 5 kHz for relative permittivity and below 200 kHz for loss coefficient. The relative permittivity decreases with increasing frequency and loss coefficient increases with increasing frequency (at frequencies above 200 kHz) for all wood species and fiber orientation. Understanding the dependencies between dielectric parameters of wood and other wood parameters at frequency range from 1 kHz to 1 MHz is important when wood is used for electrical insulation or in high-frequency drying.