Thermal conductivity measurement of industrial rubber compounds using laser flash analysis: Applicability, comparison and evaluation

In order to increase the productivity in the manufacturing of rubber components or reduce optimization cycles in mold making, injection molding simulations are intensely used in today’s polymer industry. Performing injection molding simulations of rubber parts, the thermal conductivity is a crucial material property for the precise calculation of the temperature distribution, degree of crosslinking and final part properties. The use of a Laser Flash Analysis (LFA) system is a not yet established approach for the determination of thermal conductivity of industrial rubber compounds. LFA is a transient and precise measurement technique which offers a variety of benefits, such as fast measurements (just a few seconds), multiple samples and a wide range of testing temperatures (-100°C to 500°C). The measurements are conducted using unfilled natural rubber (NR) and two natural rubber compounds containing different fillers – carbon black and silica. The applicability and challenges of LFA measurements for rubber compounds are investigated and discussed in detail. Moreover, the LFA results are compared to other commonly used methods - a Hot Disk Transient Plane Source (TPS) system and a guarded heat flow meter (GHF). This comparison allows the interpretation of the significant influence of the measuring method. The results of all compared measurements yield that LFA is a valid and precise method for the determination of thermal conductivity of industrial rubber compounds.