Thesis on CNT elastomer formation (2008 > 2011)

Dispersion of carbon nanotubes in an EPDM elastomeric matrix using soft compounding methods, towards the control of rheological and electrical properties.

Thanks to their superior mechanical and electronical properties, Carbon Nanotubes (CNT) seem to be the best nanoloads to provide composite materials with optimal properties, especially those made on the basis of elastomeric matrixes. However, nanotubes have to be well dispersed within the matrix to obtain a significant improvement of properties. The CNT dispersion in an EPM-type elastomeric matrix is examined here with the help of a random copolymer as a dispersing agent, the poly(ethylene)-co-vinyl acetate (EVA). Classic compounding tools for elastomers (the internal mixer and the roller mill), which are soft compounding methods, have been used in this research. We have shown that with a low CNT-rate in the matrix, their dispersion was controlled by two key parameters: (i) The EPM matrix viscosity and (ii) the concentration in EVA. The increase in CNT concentrations has enabled to show that rheological and electrical properties of nanocomposites suddenly vary from critically low concentration rates (the percolation threshold), that help justify the use of the selected EPM-EVA system. We therefore prepared a EPM-EVA masterbatch loaded with

20% of CNT with very good conductivity properties. Compounds made from EPDM loaded by carbon nanotubes, carbon black or a mix of both have also been analysed. We have shown that the dilution of a masterbatch provides an elastomer loaded with CNT, with a constant Mooney viscosity as well as a significant impact on the elastomer’s vulcanisation kinetics (acceleration of the reaction). A synergy effect between carbon black and CNT has been highlighted regarding mechanical properties, but not regarding the electrical ones.

This research work has been carried out within a CIFRE agreement (French Industrial Agreements for Training through Research) between EMAC company and the IPREM-EPCP laboratory. It has benefitted from the Regional Council of Aquitaine’s financial support.