Enhancement of electrically conductive network structure in cementitious composites by polymer hybrid-coated multiwalled carbon nanotube

Multiwalled carbon nanotubes (MWCNTs) could be excellent additives for electrically conductive cementitious composite (ECCC). Dispersion of MWCNTs in cement matrix is the key for promoting the electric pathways. In this work, the surface of MWCNT was modified with polyindole (PIn) and polyvinyl acetate (PVAc) concurrent admicellar polymerization (AP). The concurrent polymerization was carried out to create a bifunctional coating of a conducting polymer using PIn and a hydrophilic polymer using PVAc. The coating improves compatibility of the MWCNTs with the incipient aqueous cement matrix while facilitating conductivity of the final composite. The AP-coated MWCNTs were investigated for colloidal stability in water and electrical conductivity. It was found that using monomers of In and VAc at 0.4:1 ratio provided appropriate properties of good water dispersion (801 NTU) and high electrical conductivity (6.85 x 10(2) S/cm). To fabricate ECCC, adding 0.3 wt.% AP-coated MWCNTs in cement yielded an electrical conductivity of 8.56 x 10(-4) S/cm, more than 20 times higher than bare MWCNTs at the same concentration. AP-coated MWCNTs also enhanced compressive strength of the cement at 66.85 MPa. Field Emission Scanning Electron Microscope (FESEM) images of cement composites showed dispersion of MWCNTs and network structures in the cement matrix consistent with electrically conducting pathways. Results established that AP-coated MWCNTs created a network for electrical flow in the cement at lower concentrations for an improved ECCC.

Automated summary

The concurrent polymerization of polyindole (PIn) and polyvinyl acetate (PVAc) on the surface of MWCNTs creates a bifunctional coating that improves the dispersion and conductivity of the MWCNTs in the cement matrix. The AP-coated MWCNTs showed good colloidal stability and high electrical conductivity. Adding AP-coated MWCNTs to cement significantly increased the electrical conductivity and compressive strength of the composite, creating a network for electrical flow.