Thermal conductivity, thermal diffusivity, and specific heat capacity of particle filled polypropylene

By the addition of metal and oxide particles to plastics, thermal transport properties, heat capacity, and density of polymers can be varied systematically. Composites samples of polypropylene (PP) with various fillers in different fractions (up to 50 vol%) were prepared with an injection moulding process to study the evolution of the properties as a function of filler content. Standard filler materials like magnetite, barite, talc, copper, strontium ferrite and glass fibres were used. Thermal diffusivities, specific heat capacities and densities of the prepared composite samples were measured, and thermal conductivities were derived. Thermal conductivity of the polypropylene is increased from 0.27 up to 2.5 W/(m K) with 30 vol% talc in the polypropylene matrix. Thermal conductivities of the filled polypropylene samples are compared with the modelled values according to Hashin and Shtrikman. The interconnectivity of the particles in the polypropylene matrix is derived from a comparison between modelled and measured thermal conductivity values. For higher talc and glass fibre content in PP plastics, a complete interconnectivity is achieved, while copper particles in PP show a very poor interconnectivity. Specific heat capacities and thermal diffusivities of magnetite and barite filled polypropylene were measured in the temperature range from 300 to 395 K. (C) 2004 Elsevier Ltd. All rights reserved.