High‐Temperature Skin Softening Materials Overcoming the Trade‐Off between Thermal Conductivity and Thermal Contact Resistance

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2021-09, Vol.17 (38), p.e2102128-n/a
• Main Authors: Kim, Taehun, Kim, Seongkyun, Kim, Eungchul, Kim, Taesung, Cho, Jungwan, Song, Changsik, Baik, Seunghyun
• Format: Article
• Language: English
• Subjects: Contact resistance; elastic modulus; Heat conductivity; Heat transfer; High temperature; Modulus of elasticity; Multi wall carbon nanotubes; Nanoparticles; Nanotechnology; Silver; skin softening materials; Softening; Thermal conductivity; Thermal contact resistance; Thermal management; Thermal resistance; trade‐off; Vinyl acetate
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202102128

The trade‐off between thermal conductivity (κ) and thermal contact resistance (Rc) is regarded as a hurdle to develop superior interface materials for thermal management. Here a high‐temperature skin softening material to overcome the trade‐off relationship, realizing a record‐high total thermal conductance (254.92 mW mm−2K−1) for isotropic pad‐type interface materials is introduced. A highly conductive hard core is constructed by incorporating Ag flakes and silver nanoparticle‐decorated multiwalled carbon nanotubes in thermosetting epoxy (EP). The thin soft skin is composed of filler‐embedded thermoplastic poly(ethylene‐co‐vinyl acetate) (PEVA). The κ (82.8 W m−1K−1) of the PEVA‐EP‐PEVA interface material is only slightly compromised, compared with that (106.5 W m−1K−1) of the EP core (386 µm). However, the elastic modulus (E = 2.10 GPa) at the skin is significantly smaller than the EP (26.28 GPa), enhancing conformality and decreasing Rc from 108.41 to 78.73 mm2 K W−1. The thermoplastic skin is further softened at an elevated temperature (100 °C), dramatically decreasing E (0.19 GPa) and Rc (0.17 mm2 K W−1) with little change in κ, overcoming the trade‐off relationship and enhancing the total thermal conductance by 2030%. The successful heat dissipation and applicability to the continuous manufacturing process demonstrate excellent feasibility as future thermal management materials. The high‐temperature skin softening material is synthesized by a hard core with high thermal conductivity and a soft skin with low elastic modulus. It provides the high thermal conductivity (82.8 W m−1K−1), negligible thermal contact resistance (0.17 mm2 K W−1), and record‐high total thermal conductance (254.92 mW mm−2 K−1) for isotropic pad‐type interface materials.