Temperature dependency of electric field treatment for improvement of effective thermal conductivity of functional carbon/silicone rubber composite sheets

Abstract

Relationship between the temperature of the electric field treatment (EFT) and the improvement of the effective thermal conductivity (TC) in the out‐of‐plane direction of the carbon nanofiber (CNF)/cured silicone rubber composite sheet was investigated to elucidate the appropriate operation of the EFT. Two types of silicone rubber precursors, with viscosities of 1.3 and 58 Pa∙s, were used. The effective TC gradually increased as the temperature during EFT increased from 40 to 80 °C. However, beyond 80 °C, the effective TC started to decrease and reached the same value as that of the sheet without EFT at 100 °C. This trend was observed regardless of the rubber species or CNF content. The influence of the EFT temperature was also discussed regarding the temperature dependency of the viscoelastic properties: storage modulus, loss modulus, and complex viscosity of the uncured precursor solution. When the temperatures were set at 80 °C, no significant changes were observed in the three‐viscoelastic properties for 60 min. On the other hand, a significant increase in the viscoelastic properties was observed after 10 min at 100 °C because of the start of the curing reaction, which supported the relationship between the temperature of the EFT and effective TC.