In this presentation, epoxy/aluminium oxide powder composites designed for use as encapsulants are produced and thermally characterised. Experimental results obtained for a variety of filler concentrations, sample thicknesses and manufacturing methods are presented and compared to analytical and empirical models from the literature. Further to this, the effects of modifying analytical models using experimental data are considered. This yields models which allow the bulk thermal conductivity of these composites to be predicted more accurately than when the models were used in a purely analytical manner. Furthermore, the effect on the thermal conductivity of uneven filler distribution within the samples is considered.