A percolation model for electrical conduction in wood with implications for wood-water relations

Abstract

The first models used to describe electrical conduction in cellulosic materials involved conduction pathways through free water. These models were abandoned in the middle of the 20th century. This article re-evaluates the theory of conduction in wood by using a percolation model that describes electrical conduction in terms of overlapping paths of loosely bound or capillary water (Type II water). The model contains two physical parameters: wc, the critical moisture fraction, which is the amount of water required to form a continuous path of Type II water in wood; and σc, the conductivity of the aqueous pathways. The model gives a good fit to previously published data of the DC conductivity of wood when wc is equal to 16% moisture content and σc is equal to 0.88 S m-1. This analysis indicates that electrical conduction in wood can be explained by percolation theory and that there exists a continuous path of Type II water in wood at wc, which is below the traditional fiber saturation point. © 2008 by the Society of Wood Science and Technology.