Polymer-based composites have attracted increasing interest and been widely used in the field of electronic devices, but they are limited due to their low working temperature and dielectric instability. To date, there are few reports on improving the dielectric stability of polymer-based composites. Herein, three-dimensional boron nitrideylon 66 (3D BN/PA66) aerogels are facilely prepared for the first time by freeze-drying without templates. The BN/PA66 composites are prepared by infiltrating 3D BN/PA66 aerogels with the epoxy. The thermal conductivity of the 3D BN/PA66 composite increases to 0.6 W m ~(?1) K ~(?1) due to the formation of a BN microplatelet thermal conduction network at an ultralow BN loading of 4 vol%, which is about 5-fold and 3-fold higher than that of neat epoxy and random BN/EP composite with the same BN loading. Meanwhile, the dielectric constant variation of the BN/PA66 composites is only 6%, showing much better stability in the dielectric properties than neat epoxy and random BN/EP composites over the temperature range 25–200 °C. Our research provides a new strategy to prepare the 3D BN aerogels and proves that the 3D BN/PA66 aerogel is a potential platform for preparing polymer-based composites with excellent dielectric stability.
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