TEMPERATURE-DEPENDENCE ON THE THERMAL-CONDUCTIVITY OF POLYMERS IN THE MOLTEN STATE

An apparatus with a probe which can measure the thermal conductivity of molten polymers was constructed. The performance of the device and the temperature dependence of the thermal conductivity of various polymers were investigated. In order to apply the computer analysis and the computer aided engineering (CAE), the effects of the heat transfer by radiation on the thermal conductivity of molten polymers were studied. The optimum thermal conductivity on the mold flow was also analyzed. The thermal conductivity values of polymers in the solid phase were 0.16∼0.18 kcal/m h °C. The thermal conductivity of the polymers increased with increasing temperature. The thermal conductivity of the molten polymers eventually became ca. 39% larger than that of the solid polymers. A discontinuity of the thermal conductivity was observed at the melting temperature Tm and at the glass transition temperature Tg. The amount of heat transfer by radiation of molten polyethylene, polycarbonate, and polyoxymethylene was ca. 8∼14% of the total value of heater. The heat transfer by radiation was considered in the thermal conductivity analysis with a computer and the CAE. The accuracy of measurement was within ± 3∼4% in the molten state polymers. This value is ca. 7% higher than that measured using a concentric cylinder device. © 1990, The Society of Polymer Science, Japan. All rights reserved.