The Thermal Diffusivity and Conductivity of Natural Rubber Compounds

Abstract

Abstract New methods of measuring the conductivity and diffusivity of rubbers from ambient to 250°C have been developed. The method of measuring diffusivity described in this paper is simple to use and very much quicker than previous methods, the whole temperature range being covered in about half an hour. The accuracy is about 5%. Two disk-shaped samples are used, 48 mm diameter and 2 mm thick, but the geometry can be changed to accommodate samples of varying thickness. The method is suitable for anisotropic samples but, because the measurement is made over a small area, they must be homogeneous. Diffusivity and conductivity measurements have been made on a series of carbon-black-loaded natural rubber compounds. Both thermal properties depend on temperature, type of rubber, and the type and quantity of carbon black. Empirical equations have been obtained relating diffusivity and conductivity to temperature and black loading. These fit the data to better than 10%.