Significantly anisotropic thermal conductivity improvement of PEEK composites with EMI shielding effectiveness

Abstract

The demand for polymeric composite materials with multifaceted performance has increased with rapid advancements in various sectors such as energy storage, 5G technology and electronic thermal management. Polyetheretherketone (PEEK), a thermoplastic polymer with superior mechanical properties, solvent resistance and thermal stability, is an ideal substrate for composite materials. However, traditional filler-reinforced PEEK composites often struggle to achieve the desired thermal conductivity due to filler agglomeration resulting in high interfacial thermal resistance (ITR). To address these issues, laminated (NH₂-GnPs&MWCNTs)/PEEK composite films were fabricated by electrostatic spraying technique and hot pressing process, with hybrid fillers that interconnected to form a compact heat-conducting network. Amino-functionalised graphene was also incorporated, which enhanced the interfacial compatibility and reduced the ITR of composites. At a filler content of only 14.97 vol%, the in-plane and through-plane thermal conductivities of (NH₂-GnPs&MWCNTs)/PEEK composite films reached 4.05 and 2.05 W m⁻¹ K⁻¹, respectively, by factors of 17.6 and 8.9 over pure PEEK matrix with a thermal conductivity of 0.23 W m⁻¹ K⁻¹. The Agari and Foygel models demonsrated that the composites formed an efficient three-dimensional conduction network and exhibited a reduced ITR. It is confirmed that the strategically synergistic fillers and electrostatic spraying laminated structure form a highly interconnected three-dimensional conduction network with some degree of orientation, thereby mitigating the interface scattering and increasing the mean free range of phonons. In addition, the composites displayed excellent electromagnetic interference-shielding capabilities and thermal stability, positioning them as dual-functional thermal management materials with significant application potential.