Simultaneous improvement of thermal conductivity and mechanical properties for mechanically mixed ABS/h‐BN composites by using small amounts of hyperbranched polymer additives

Recently, thermal interface materials (TIMs) are in great demands for modern electronics. For mechanically mixed polymer composite TIMs, the thermal conductivity and the mechanical properties are generally lower than expected values due to the sharply increased viscosity and poor filler dispersion. This work shows that addition of a small amount of polyester‐based hyperbranched polymer (HBP) avoided the trade‐off in mechanically mixed ABS/hexagonal boron nitride (h‐BN) composites. After adding 0.5 wt% HBP, the maximum h‐BN content in the composites increased from 50 to 60 wt%. The out‐of‐plane, in‐plane thermal conductivity, and tensile strength of ABS/h‐BN with 50 wt% h‐BN were 0.408, 0.517 W/mK, and 18 MPa, respectively, and were increased to 0.729, 0.847 W/mK, and 32 MPa by adding 0.5 wt% HBP, while 0.972, 1.12 W/mK, and 29.5 MPa were achieved for ABS/h‐BN/HBP with 60 wt% h‐BN. The morphological and rheological results proved that these enhancements are due to the improved h‐BN dispersion by decreasing viscosity of composites during mixing. Theoretical modeling based on the modified effective medium theory confirmed such results and showed that the interfacial thermal resistance also decreased slightly. Thus, this work demonstrates a facile and scalable method for simultaneously improving the thermal conductivity and mechanical properties of thermoplastic‐based TIMs.