Highly Thermal-Conductive TPU/h-BN Composites with Filler Alignment and Interfacial Optimization Induced by Cyclic Pulsating Pressure

With the development of the 5G era, the demand for lightweight and highly integrated smart devices has imposed more stringent requirements on thermal management materials. Polymer-based thermally conductive composites have attracted significant attention due to their wide applicability, ease of processing, and low cost. However, since high thermal conductivity (TC) generally depends on high filler loadings that compromise flexibility, it remains imperative to realize both thermal and mechanical performance at low filler contents. In this work, we propose a cyclic pulsating pressure (CPP) technique to simultaneously enhance the thermal conductivity and mechanical performance of composites at low filler loadings. By optimizing the duration of the pressure release stage (Toff) in the CPP process, h-BN flakes were effectively induced to reorient and align within the TPU matrix. The resulting composite with 30 wt % h-BN exhibited a thermal conductivity of 2.03 W/(m·K), representing a 534% improvement over neat TPU and 80% increase compared to the static pressure (SP) sample. This improvement is attributed to the formation of continuous and efficient thermal pathways between h-BN and the reduction of interfacial thermal resistance (ITR). When applied as a thermal interface material (TIM) between a light-emitting diode (LED) and a heat sink, the composite significantly improved the heat dissipation performance. This work provides an efficient, green, and scalable strategy for fabricating high-thermal-conductivity polymer-based TIM with a low filler content.