Carbon Nanotubes with Carbon Blacks as Cofillers to Improve Conductivity and Stability

In this study, a simple solution-mixing method is used to develop a kind of excellent flexible, electrically conductive adhesives (ECAs). Carbon nanotubes (CNTs) and carbon blacks (CBs) as cofillers were added into Ag-based pastes. The use of the two fillers is due to the consideration that these two materials may provide positive synergistic effects for improving the conductivity of ECAs. The conductivity, flexibility, cyclability, and oxidation resistance of ECAs with different contents of carbon fillers were studied. It was found that a small amount of CNTs or CBs can dramatically improve the ECAs' conductivity. Solution-mixing method brings excellent carbon nanofiller dispersion in polymer matrix. Highly dispersed CNTs and CBs among the Ag flakes formed three-dimensional conducting networks to improve the conductivity of ECAs. The conductivity of ternary hybrid ECAs (with addition of 3 wt % CNTs and 2 wt % CBs) with a low content of 55 wt % Ag flakes is higher than that of the ECAs filled with only the Ag content over 65 wt %. Meanwhile, by selecting thermoplastic polyurethane resin as the matrix, the ECAs exhibited excellent mechanical compliance. The resistivity did not change when the ECAs were bended at a 60% flexural strain or pressed under 1200 kPa. Additionally, the adhesion strength of the new composited ECAs is better than that of a commercial ECA (Abletherm 3188). Further, no obvious conductivity change was observed when the sample was stored in ambient air condition at 80 °C and 60% relative humidity (60%) for 15 days.