Comparative study of the structure and properties in 3D-BNNT/EP thermally conductive composites prepared by powder hybrid compression molding and ice-templating methods

The creation of thermally conductive pathways in polymers is crucial for achieving high thermal conductivity in composites. In this study, a novel ultrafine and ultrathin-walled boron nitride hollow nanotube (BNNT) was employed to fabricate two types of 3D-BNNT/EP composites, 3D-BNNT/EP-p and 3D-BNNT/EP-f, prepared via powder hybrid compression molding and ice-templating methods, respectively. The experimental results show that the 3D-BNNT/EP-p composites exhibit high performance at high BNNT loading (55.87 wt%). The in-plane thermal conductivity reached 1.091 W/(m K), representing a 590% enhancement over pure epoxy resin (0.185 W/(m K)), while the T 60% decomposition temperature increased by 63 °C, indicating superior thermal conductivity and stability. Practical application tests reveal that this material can reduce the maximum operating temperature of LED devices by 11.3 °C, demonstrating its heat dissipation advantages. In contrast, the ice-templated composites showed higher filler efficiency at low BNNT loading (10.18 wt%), achieving an 89% improvement in in-plane thermal conductivity. However, their 3D network contained CMC-Na binder, leading to discontinuous thermal pathways and only a 24 °C improvement in thermal stability. Dielectric property measurements confirmed that both types of composites maintained the low-dielectric characteristics of the epoxy matrix, with the compression-molded samples exhibiting more stable dielectric loss behavior at high frequencies. Finite element simulations verified the thermal enhancement mechanism of 3D-BNNT networks and highlighted the impact of processing methods on performance. These findings provide both a theoretical foundation and practical guidance for the selection and design of high-performance thermal management materials in advanced electronic and optoelectronic devices.