Thermal properties of melt polymers by the hot wire technique

Abstract

Over recent years mathematical modelling has become an established tool for improving process control and product quality in polymer processing. As models become more sophisticated, there is an increasing need for reliable thermophysical properties data. Those properties are observed when heat is added or removed from a material, and they become important in any project that must function in any thermal environment. Thermal conductivity, thermal diffusivity and specific heat, namely the thermal properties, are the three most important physical properties of a material that are needed for heat transfer calculations. Reliable thermal properties values are essential for polymers, both in steady and non-steady state situations. Recently, transient techniques have become the preferable way for measuring thermal properties of materials. In this work, the hot wire parallel technique is employed in the experimental determination of the thermal properties of polymers. Samples are prepared through the extrusion process starting from the powder or pellets of the solid polymer. A special mould of stainless steel in the shape of a rectangular parallelepiped provided with ceramic insulators between the hot wire, thermocouple and the mould is employed to store the melt extruded polymer whose thermal properties will be measured. Measurements are carried out from room temperature up to approximately 50 °C above the crystalline melting point. Thermal conductivity, specific heat and thermal diffusivity experimentally determined are checked against data found in literature and those furnished by the manufacturers.