A novel device for measuring the thermal conductivity of polymeric materials (pure polymers or nanocomposites) is presented here. Its design is based on two cylindrical tanks containing cold and hot water. Each tank wets one side of a disc-shaped polymeric sample. The proper selection of construction materials (aluminum body, Teflon fittings, etc.) and geometry (shape, size, etc.) of the two tanks and of the sample (diameter, thickness) renders the accurate measurement of the low thermal conductivity of several polymeric materials possible. The disc-shaped sample is placed in-between the two cylindrical tanks of the device, filled with cold and hot water. The water temperature in the two tanks is an adjustable operational parameter of the device. Both tank temperatures are recorded and fitted by a proper mathematical model in order to estimate the thermal conductivity of the sample. Extensive experimentation shows a very small scatter of the estimated conductivity values. The device was used to measure thermal conductivity of several polymers such as silicone rubber and epoxy resin prepared with a variety of cross-linkers and cross-linker blends. Moreover, the above polymers are used as matrices for the incorporation of various (nano)additives, like mesoporous silica foams (MCF) and organoclays (I.30E), for the preparation of the relative polymer nanocomposites whose thermal conductivity is measured. (C) 2017 Elsevier Ltd. All rights reserved.