Nano-bridge effect on thermal conductivity of hybrid polymer composites incorporating 1D and 2D nanocarbon fillers

• Published in: Composites. Part B, Engineering Engineering, 2021-10, Vol.222, p.109072, Article 109072
• Main Authors: Jang, Ji-un, Lee, Seung Hwan, Kim, Jaewoo, Kim, Seong Yun, Kim, Seong Hun
• Format: Article
• Language: English
• Subjects: Analytical modelling; Particle-reinforcement; Polymer-matrix composites (PMCs); Thermal analysis; Thermal properties
• ISSN: 1359-8368; 1879-1069
• DOI: 10.1016/j.compositesb.2021.109072

Numerous studies have been reported on thermal interface materials based on synergistic hybrid effects, however, most of them contain only fragmentary experimental results and the related model has been rarely proposed to explain the effects exactly. Herein, the thermal conductivities of the composites were systematically evaluated according to various filler contents and ratios. It was found that the fraction of the secondary filler inducing the maximum synergistic effect decreased as the total filler content increased. In addition, when the fraction was higher than the optimum fraction, the anti-synergistic effect occurred. At the optimum fraction, effective phonon transfer was induced due to the improved filler network formation of graphene nanoplatelet (GNP)-carbon nanotube (CNT), thereby achieving high thermal conductivity of 7.69 W/m·K at fGNP = 27.69 vol% and fCNT = 0.57 vol%. Moreover, the Kim-Jang-Lee (KJL) model for the synergistic effect was proposed by introducing filler-ratio variables into the critical percolation equation reported previously, and the KJL model for the anti-synergistic effect was proposed based on the rule of mixture of composites filled with the optimal connected filler network and filled with the excessive secondary filler. [Display omitted] •Optimum filler ratio determining hybrid effects was revealed.•Switching mechanism on synergistic and anti-synergistic effects was identified.•Synergistic increase in thermal conductivity was caused by the nano-bridge.•Excessive secondary filler in nanocomposites caused an anti-synergistic reduction.•New KJL model for the nano-bridge effect was proposed.