Effects of Orientational Relaxation of Polymer Chains Induced by Isotropic Particles on the Enhanced Thermal Conductivity of AlN-filled Polyimide Films

Abstract

A series of composite films composed of m-sized aluminum nitride (AlN) particles and polyimides (PIs) were fabricated using (a) rigid-chain sBPDA-PPD (sBPPD) PI and (b) flexible-chain sBPDA-ODA (sBPOD) PI as matrices. The relationship between their morphological structures and thermophysical properties were investigated by analyzing cross-sectional SEM images and by measuring out-of-plane thermal conductivity (TC  ) and in-plane coefficients of thermal expansion (CTE // ). The sBPPD chains exhibited a better polymer-filler packing behavior due to their rigid structure having small free volume. Both TC  and CTE // of AlN-filled sBPPD films showed positive deviations from theoretical predictions, whereas no such behavior was observed in AlN/sBPOD composites or in sBPPD films filled with highly anisotropic hexagonal boron nitride (hBN) flakes. The enhanced TC  and CTE // observed for the sBPPD composites can be attributed to a significant change in the orientational state of the PI chains; in-plane orientated sBPPD chains in the pristine PI film become distorted by incorporation of isotropic AlN particles.

Fabrication of oriented hBN scaffolds for thermal interface materials

“…11 The CTE of hBN microplatelets is also anisotropic, À2.7 ppm K À1 along the in-plane direction and 38 ppm K À1 along the outof-plane direction, 10 and it is efficient in reducing the CTE of the composites. 13,40,41 Fig. 4a reveals that along the z direction, the CTE of Composite A decreased dramatically with the increased loading, and is lower than 100 ppm K À1 .…”

Thermal Conductivity for Polymer Composite Materials: Recent Advances in Polyimide Materials

“…Moreover, AlN has also received much attention for use as the thermal conductive ceramics llers to be mixed with polymer materials including PI. Tanimoto and Ando (2014) investigated the relationship between morphological structure and thermophysical properties such as the TC of PI-based composites that consist of micrometer-sized AlN particles. Two types of PIs with either rigid chains (3,3′ ,4,4′-biphenyltetracarboxylic dianhydride (sBPDA)-p-phenylene diamine (PPD), sBPPD) or exible chains (sBPDA-ODA, sBPOD) were used.…”