High thermal conductivity graphite film/polyimide composites based on enhanced interfacial bonding

High thermal conductive graphite film (GF) has received great attention in mobile electronic devices, owing to its exceptional thermal conductivity. However, the smooth surface of the GF leads to poor interfacial bonding with the matrix and thus high interfacial thermal resistance, thereby limiting its practical application. To address this issue we proposed a facile and novel cross-stacking strategy to fabricate three different high performance polyimide/GF (PI/GF) composites through thermal compression of modified GF with three different types of soluble PI. Notably, the combination of high-temperature oxidative etching of GF and the introduction of flexible siloxane chains into the PI maximizes the enhancement of interfacial bonding in the composite. This is attributed to the introduced siloxane segments promote the formation of a flexible interfacial layer, which reduces thermal resistance by increasing the contact area while simultaneously improving interlaminar shear strength (ILSS) through stress absorption and dispersion. As a result, the flexible siloxane chain segments polyimide/GF (SPI/GF) composite with a GF volume fraction of 94.5% achieves a high through-plane thermal conductivity of 1543 W/(m·K), along with an ILSS of 1.92 MPa, which represents a 146.2% improvement over the bismaleimide resin/GF (BMI/GF) composite. Therefore, this work provides a facile strategy to enhance interfacial bonding in composites, which concurrently improves both thermal conductivity and mechanical properties, making the materials well-suited for demanding applications such as in aerospace and advanced equipment.