High-performance conductive polyurethane adhesive by filling carbon nanotubes. Electrical, thermal and rheological characterization

Résumé

The present work is focused on the manufacturing and the characterization of the polyurethane/carbon nanotubes as their use as electrically conductive adhesives.Nanocomposites are manufactured with MWCNT content between 0.5-8 wt. % MWCNT blended by melt mixing method. The influence of MWCNT on the rheological, electrical, morphological, thermal and adhesive properties is studied.The effect of the MWCNTs is clearly observed in the viscoelastic terminal zone, reflecting the obstruction caused to the motion of the polymer chain as a whole. The formation of a combined polymer/MWCNT network gives rise to a frequency independent storage modulus values. This marks the rheological rigid percolation threshold at an amount of 1.5 wt. % MWCNT at 100 ºC. The PUR/MWCNTnanocomposites exhibit similar processability than neat PUR in terms of shear viscosity at high shear rates. The effect of electrical conductivity has also been study obtaining an electrical percolation threshold in the molten state and in the solid state which is 0.85 wt. % MWCNT. On the other hand, by means of electrical measurements an electron hopping tunneling mechanism is confirmed, as has been reported in literature for similar nanocomposites.As a general conclusion it can be stated that these materials are good candidates to develop Hot Melts ECAs, since they display satisfactory properties with regard to viscosity, extrudability, tack, crystallization (linked to a permanent adhesion), and an electrical conductivity.