Single‐walled carbon nanotubes/polycarbonate composites: basic electrical and mechanical properties

Abstract

The focus of this paper is to investigate the electrical conductivity and the mechanical properties of single-walled carbon nanotubes/polycarbonate composites. Two different direct incorporating methods were applied. In the first method PC and SWCNTs were mixed with different ratios in a small scale conical twin screw extruder. Here, additional variations in the feeding of the filler material were tested in order to improve the state of dispersion of the melt mixing method. The second one is the coagulation method, here, the filler material was suspended and the polymer material was dissolved in liquid organic substances. The mechanical properties were examined by tension tests and by measuring the Vickers hardness. It should be stressed, that the nanofiller material was provided in large batches (m > 100 g) and extensively mechanically homogenized in order to eliminate quality fluctuations and density differences in the SWCNT occurrences. The filler material was synthesized in a Krätschmer reactor (carbon arc). After homogenization, the nanomaterial was characterized. Based on this the SWCNT content was estimated to be between 30 and 40%, which is usual for arc discharge material.

A strategy for achieving low percolation and high electrical conductivity in melt-blended polycarbonate (PC)/multiwall carbon nanotube (MWCNT) nanocomposites: Electrical and thermo-mechanical properties

“…If nanofillers are randomly distributed, then the mean average distance (d) among the nanofillers would be barrier width. This mean average distance is considered, in the first approximation, to be directly proportional to the nanofillers concentration in weight, p -1/3 and can be expressed by the following Equation (10) [24]: (10) Thus, the combination of the Equations (9) and (10), shows that tunneling assisted conductivity (log! DC ) is directly proportional with p -1/3 and expressed by the following Equation (11): (11) Figure 1c shows the linear variation of log!…”

“…PC has high impact resistance, toughness, dimensional stability and good optical clarity, and is mostly used in many engineering applications. PC has been modified by blending with various polymers for different applications and compounding with different kinds of CNTs to enhance the electrical, mechanical and thermal properties of the PC [9][10][11][12]. For instance, Wu et al [9] have observed electrical conductivity of 2!10 -8 S·cm -1 with 2 wt% loading of MWCNT in melt blended PC/MWCNT nanocomposites, prepared by diluting solution blended PC/carboxylic acid functionalized MWCNT (10 wt%) mixture.…”

“…For instance, Wu et al [9] have observed electrical conductivity of 2!10 -8 S·cm -1 with 2 wt% loading of MWCNT in melt blended PC/MWCNT nanocomposites, prepared by diluting solution blended PC/carboxylic acid functionalized MWCNT (10 wt%) mixture. Hornbostel et al [10] reported the percolation threshold of melt blended PC/ MWCNT nanocomposites in between 1.5 to 2.0 wt% loading of MWCNT. Sathpathy et al [11] have studied the electrical conductivity of melt blended PC/MWCNT nanocomposites and electrical conductivity of 2!10 -8 S·cm -1 was achieved at 2 wt% loading of MWCNT, prepared by diluting a PC/ MWCNT (15 wt%) mixture.…”

Electromagnetic Interference Shielding Efficiency in the Range 8.2-12.4 GHz of Polymer Composites with Dispersed Carbon Nanoparticles

“…In case of graphite nanoparticles and carbon black the content was not sufficient to reach the percolation threshold, therefore no conduction network was formed and SE was low. Depending on carbon black properties percolation thresholds in polycarbonate matrix were found to be from 5 to 10 w% [9], and SE values of 10 dB for carbon black/rubber composites were measured at loadings higher than 30 w% [4]. Concerning CSCNT, their high electrical conductivity together with high aspect ratio (ratio of length to diameter is more than 20) and uniform dispersion in the PMMA can lead to formation of conducting network even at very low loadings (less than 1 w%), in the same way as was observed for MWCNT [5,10] and SWCNT [9], and as a result to the higher SE.…”

“…Depending on carbon black properties percolation thresholds in polycarbonate matrix were found to be from 5 to 10 w% [9], and SE values of 10 dB for carbon black/rubber composites were measured at loadings higher than 30 w% [4]. Concerning CSCNT, their high electrical conductivity together with high aspect ratio (ratio of length to diameter is more than 20) and uniform dispersion in the PMMA can lead to formation of conducting network even at very low loadings (less than 1 w%), in the same way as was observed for MWCNT [5,10] and SWCNT [9], and as a result to the higher SE. Comparing to the data for MWCNT / polypropylene composites, reported in [5], the values of SE measured in the present work for CSCNT/PMMA composites are lower, that can be explained by lower electrical conductivity of CSCNT in comparison with MWCNT, but this requires additional studies.…”