Modelling of Effective Thermal Conductivity of Composites Filled with Core-Shell Fillers.

Jan Czyzewski,Robert Sekula,Andrzej Rybak,Czeslaw Kapusta,Karolina Gaska

doi:10.3390/ma13235480

Abstract

An effective model to calculate thermal conductivity of polymer composites using core-shell fillers is presented, wherein a core material of filler grains is covered by a layer of a high-thermal-conductivity (HTC) material. Such fillers can provide a significant increase of the composite thermal conductivity by an addition of a small amount of the HTC material. The model employs the Lewis-Nielsen formula describing filled systems. The effective thermal conductivity of the core-shell filler grains is calculated using the Russel model for porous materials. Modelling results are compared with recent measurements made on composites filled with cellulose microbeads coated with hexagonal boron nitride (h-BN) platelets and good agreement is demonstrated. Comparison with measurements made on epoxy composites, using silver-coated glass spheres as a filler, is also provided. It is demonstrated how the modelling procedure can improve understanding of properties of materials and structures used and mechanisms of thermal conduction within the composite.

Highlights

Heat management is one of the key challenges in electronic and power devices
A model to calculate thermal conductivity of composites with core-shell type fillers was developed based on the Lewis-Nielsen formula for the filled systems and the Russel model of thermal conductivity of porous materials
It was shown that the Russel model, originally developed for a continuous porous material, can be used to describe the effective thermal conductivity of a single core-shell filler grain

Summary

Introduction

Heat management is one of the key challenges in electronic and power devices. Effective heat dissipation is needed to achieve required ratings. This, in turn, requires high thermal conductivity of the applied electric insulation, structural, and packaging materials [1]. Thermal conductivity of composites has been extensively studied and it depends on that of the polymer matrix, that of the filler material, filling degree, filler grain shape, and their mutual arrangement. The filler-matrix interfacial thermal resistance can influence the thermal conductivity [5]. This is important at cryogenic temperatures [6], and for nano-fillers, at room temperature [7]. Insulating fillers of high thermal conductivity are of particular interest since they can improve the thermal conductivity of the composite material, while maintaining its electrically insulating properties.

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Results

Conclusion