Effect of processing methods on electrical percolation and electromagnetic shielding of PC/MWCNTs nanocomposites

Abstract

Nanocomposites of polycarbonate (PC)/multiwalled carbon nanotubes (MWCNTs) containing 0.5-3 wt% of MWCNTs were prepared via two methods of melt mixing and solution mixing. The effect of CNT content and processing methods on electrical and electromagnetic properties of nanocomposite samples were investigated. TEM microphotographs revealed that the PC/ MWCNT composites prepared by the solution method, have better dispersion and distribution of CNTs in the PC matrix. Electrical measurements indicated an electrical percolation threshold of less than 1 wt% of CNTs for this system. Also, it was found that PC/MWCNT composites prepared by the solution method, exhibit higher electrical conductivity and lower electrical percolation threshold. The electromagnetic interference shielding effectiveness (EMI SE) measurements in the X-band (8.2-12.4 GHz) indicated that EMI SE is increased by increasing the amount of CNTs in the samples, and also the thickness of specimens. In addition, the results showed that the composites prepared by the solution method, have higher SE values. Finally, in order to reach an acceptable value for commercial applications of EMI shielding materials (20 dB), thicker samples were produced and it was found that the 3.5 mm thick samples containing 2 wt% CNTs, have a 19.6 dB shielding effectiveness. POLYM. COMPOS., 38:E269-E276,

A review of the interfacial characteristics of polymer nanocomposites containing carbon nanotubes

“…22 The percolation threshold for the electrical conductivity in these composites is closely related to the dispersion state of carbon nanotubes, 248,300-303 alignment, 304,305 dimensions (e.g., length and diameter) of carbon nanotubes, 300,303,[306][307][308][309][310] degree of modication of the surface of carbon nanotubes, [310][311][312] type of polymers, 313 and composite processing method. 300,[314][315][316] The percolation threshold is strongly dependent upon the degree of the dispersion of carbon nanotubes. Additionally, alignment of carbon nanotubes plays an important role in determining the electrical conductivity of the nanocomposite and its percolation threshold.…”

Melt‐mixed carbon nanotubes/polymer nanocomposites

“…It can be concluded from the above discussion that the rheological percolation threshold can be achieved at lower concentration of CNTs as compared to electrical percolation threshold. However, for PS/MWCNTs composites, it was observed that the rheological percolation threshold (between 0.9 wt% and 1 wt% of CNTs) was achieved at higher concentration of CNTs as compared to its electrical percolation threshold …”

“…The value of electrical percolation for melt-mixed PS/MWCNTs composite was observed to be between 0.5 wt% and 0.6 wt% of MWCNT, [13] for PC/MWCNTs it was around 0.84 wt% of MWCNTs, [14] between 1 wt% and 2 wt% of MWCNTs for PP/MWCNTs composites, [15] and above 2.5 wt% of MWCNTs for PA6/MWCNTs. [16] Apart from interfacial interaction factor, the second most important factor which dictates the extent of dispersion of MWCNTs in polymer matrix is the melt viscosity of the matrix.…”

“…However, for PS/MWCNTs composites, it was observed that the rheological percolation threshold (between 0.9 wt% and 1 wt% of CNTs) was achieved at higher concentration of CNTs as compared to its electrical percolation threshold. [14] It is important to get lower percolation threshold in order to achieve good dispersion, processability, and improved properties of the composites. Selective localization of CNTs in a particular polymer phase for a specific immiscible polymer blend also leads to composites with low percolation threshold.…”

Highly conductive PP/PET polymer blends with high electromagnetic interference shielding performances in the presence of thermally reduced graphene nanosheets prepared through melt compounding

“…The interference of EM radiations can disturb the routine performance or cause the complete failure of equipments . Thus, electromagnetic interference (EMI) shielding of radio frequency radiation is still a serious concern for modern society . In this regard, developing cost effective and lightweight EMI shielding materials to minimize EMI have received considerable attention in recent years.…”