Study on the effect of carbon nanotube on the properties of electrically conductive epoxy/polyaniline adhesives

Electrically conductive hybrid epoxy (EP) adhesives filled with p-toluenesulfonic acid (PTSA) doped polyaniline (PANI) and carbon nanotubes (CNT) were prepared and their electrical, thermal and morphological properties were investigated. The CNT was incorporated in EP/PANI (1, 3, 5, 7, 10 and 15 wt%) to obtain hybrid composites aiming to achieve better conductivity. Percolation threshold in EP/PANI and EP/CNT binary composites achieved was at around 5% of PANI and 0.2% CNT, respectively. It was observed that the addition of 0.1% CNT in EP/PANI (5%) composites improved the electrical conductivity of composites with a minimal effect on lap shear strength. Differential scanning calorimetry (DSC) studies revealed that while 0.1% CNT addition had an insignificant retardation effect on the curing of EP/PANI (5%), it increased the glass transition temperature (Tg) of cured sample significantly. Although, incorporation of PANI increased the thermal stability of epoxy significantly, addition of CNT further enhanced it marginally in the temperature range of 200–400 °C. FT-IR and XRD spectra of PANI/CNT hybrid fillers system showed molecular level interaction and good dispersing ability of CNT with PANI, respectively. Interestingly, morphological studies showed good dispersion of PANI and CNT in epoxy matrix in binary composites as well as in hybrid composites with no phase separation between PANI and CNT. Optical micrographs showed better dispersion of hybrid PANI/CNT filler system within epoxy matrix compared to PANI only.