Phase-Change Polymer–Metal Composites with Tunable Thermal Conductivity and Their Additive Manufacturing

Polymer–metal composites that combine a soft polymer matrix with low-melting-point metal/alloy particles that can be melted within a compatible temperature range hold great promise for multifunctional additive manufacturing (AM). The reversible melting–solidification phase transition of the metal component, coupled with the mechanical flexibility and stretchability of the polymer matrix, enables thermally responsive and mechanically tunable composites suitable for 3D printing. However, a fundamental understanding of their thermal, rheological, and morphological behaviors remains limited. In this work, we investigate a series of polymer–metal composites composed of Field’s metal (FM) and thermoplastic elastomers (TPE), with the goal of elucidating the critical structure–property relationships for material extrusion-based AM. Thermo-rheological analyses reveal distinct temperature-dependent transitions strongly influenced by FM content and processing conditions. X-ray diffraction and electron microscopy further demonstrate significant process-dependent morphological evolution. Notably, these composites exhibit highly tunable thermal conductivity, achieving values up to 19 W m–1 K–1 after the postprinting processing. Successful 3D printing via pellet extrusion reveals substantial differences in thermal, rheological, and mechanical properties compared to solution-cast counterparts, primarily due to shear-induced morphological rearrangement during printing. The insights gained into the key structure–property relationships of these 3D-printable multifunctional FM–TPE composites pave the way for their potential applications in thermal management, soft electronics, and robotics.