For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based composite materials with high thermal conductivity. The inorganic fillers, however, are often available only in submicron- and micron-scaled dimensions and, consequently, can sediment during the curing reaction of the polymer matrix. In this study, an epoxy/amine resin was filled with nano- and submicron-scaled alumina particles, yielding a gradient composite. It was found that the thermal conductivity according to laser flash analysis of a sliced specimen ranged from 0.25 to 0.45 W·m⁻¹·K⁻¹ at room temperature. If the thermal conductivity of an uncut specimen was measured with a guarded heat flow meter, the ‘averaged’ thermal conductivity was measured to be only 0.25 W·m⁻¹·K⁻¹. Finite element analysis revealed that the heat dissipation through a gradient composite was of intermediate speed in comparison with homogeneous composites exhibiting a non-gradient thermal conductivity of 0.25 and 0.45 W·m⁻¹·K⁻¹.

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.