Effect of Surfactants and Manufacturing Methods on the Electrical and Thermal Conductivity of Carbon Nanotube/Silicone Composites

Abstract

The effect of ionic surfactants and manufacturing methods on the separation and distribution of multi-wall carbon nanotubes (CNTs) in a silicone matrix are investigated. The CNTs are dispersed in an aqueous solution of the anionic surfactant dodecylbenzene sulfonic acid (DBSA), the cationic surfactant cetyltrimethylammonium bromide (CTAB), and in a DBSA/CTAB surfactant mixture. Four types of CNT-based composites of various concentrations from 0 to 6 vol.% are prepared by simple mechanical mixing and sonication. The morphology, electrical and thermal conductivity of the CNT-based composites are analyzed. The incorporation of both neat and modified CNTs leads to an increase in electrical and thermal conductivity. The dependence of DC conductivity versus CNT concentration shows percolation behaviour with a percolation threshold of about 2 vol.% in composites with neat CNT. The modification of CNTs by DBSA increases the percolation threshold to 4 vol.% due to the isolation/separation of individual CNTs. This, in turn, results in a significant decrease in the complex permittivity of CNT–DBSA-based composites. In contrast to the percolation behaviour of DC conductivity, the concentration dependence of thermal conductivity exhibits a linear dependence, the thermal conductivity of composites with modified CNTs being lower than that of composites with neat CNTs. All these results provide evidence that the modification of CNTs by DBSA followed by sonication allows one to produce composites with high homogeneity.

Tailoring electrical and thermal properties of polymethyl methacrylate‐carbon nanotubes composites through polyaniline and dodecyl benzene sulphonic acid impregnation

“…There is a sharp increase in conductivity of the PMMA at very low filler addition which indicates the strong networking among the CNTs in the matrix due to the good dispersion of DBSA decorated CNTs. As DBSA is an anionic surfactant and found to be helpful in the homogeneous dispersion of CNTs in PMMA matrix by forming hydrophobic linkage between the CNTs and the alkyl chains of DBSA . Overall, in both types of fillers, percolation was observed at relatively low wt% with improved maximum conductivity values, which helps in tailoring the electrical properties of PMMA.…”

“…Highest value of dielectric constant measured for DBSA‐CNT/PMMA composite is found to be 2.2 at 0.8 wt% of CNTs. It is reported that charge elimination effect is weak in small cluster‐based composites and electric field intensity is higher with bigger clusters . As SEM images show that DBSA‐CNTs forms small clusters and PANI‐CNTs appear as big clusters, the value of dielectric constant is higher for PANI‐CNTs/PMMA composites than DBSA‐CNTs/PMMA ones.…”

“…The suspended solution was then filtered by using PTFE filter paper and washed several times with distilled water. This filtrate was dried at 60°C for 14 h . Dried product was finely grounded and used as filler II for PMMA matrix in the same pattern as above to obtain the DBSA‐CNTs/PMMA composites with different percentage concentrations of fillers and matrix .…”

Surfactant Incorporated Co Nanoparticles Polymer Composites with Uniform Dispersion and Double Percolation

“…With addition of CoNPs with and without DBSA, in the PMMA matrix, the absorption is increased showing incorporation of CoNPs in the structure of PMMA. This increase in the absorption intensity was more pronounced in the case when DBSA was added as an additive which clearly indicated that DBSA helped in better incorporation of CoNPs [4,19,21]. It can be noted that shift in the position of maximum absorption is not significant.…”

“…It is low-cost polymer with extraordinary environmental stability and ability to form thin layers with good mechanical strength. It is believed that DBSA as surfactant will play its role in the better dispersion of CoNPs in PMMA so that characteristics of the CoNPs can be imparted in PMMA more effectively [18][19][20]. This will help in reducing the chances of agglomerate formation of CoNPs.…”