Effect of multi-walled carbon nanotube dispersion on the electrical, morphological and rheological properties of polycarbonate/multi-walled carbon nanotube composites

Tensile, rheological and morphological characterizations of multi-walled carbon nanotube/polypropylene composites prepared by microinjection and compression molding

Polypropylene (PP) reinforced with 2 and 4 wt% of multi-walled carbon nanotubes (MWNT) were melt-blended in twin screw extruder and then molded by compression or micromolding process. The impact of injection speed on the surface morphology, rheological and tensile characteristics was investigated by using a scanning electron microscope, parallel plate rheometry, and tensiometry. Results showed that the tensile properties of micro-molded specimens were remarkably higher than those of the compression molded sheets. Compared to compression molded sheets, micromolded specimens demonstrated up to 40 and 244% higher tensile stiffness and yield strength, respectively, most likely due to the alignment of polymer chain segments in the flow direction induced during the micromolding process. It was observed that the fast filling speed caused a drop in the tensile properties of the nanocomposites and polymer. Rheological examination revealed that the presence of a rheological percolation network in the nanocomposites produced by micromolding and the fast injection speed was beneficial for establishing the percolated network. Morphological examination revealed that the size of nanotube agglomerations that appeared in micromolded specimens was up to five times smaller than in compression molded sheets and the agglomeration size decreased with the increase of the injection speed.

Factors that Affect Network Formation in Carbon Nanotube Composites and their Resultant Electrical Properties

This review paper explores the formation of carbon nanotube (CNT) polymer composites as a function of material and processing parameters. The effect of different polymer systems, increasing multiwall CNT content, modification of CNTs, processing conditions, and aspect ratio are discussed in detail for multi-walled carbon nanotubes (MWCNT) composites along with some examples for SWCNT composites. All of these factors influence the microstructure and how the network of CNTs forms within it. Often, researchers choose to modify the CNTs to aid in their distribution; however, this may result in a reduction or increase in conductivity depending on many factors. The electrical properties are directly affected by changes in the CNT network and how the material has been processed. As soon as the network forms, percolation occurs and the conductivity increases. In order to understand how to control the properties of CNT composites, all material characteristics and processing conditions must be taken into account.

The Processing Behavior of Liquid Sn/Molten Polyethylene during Internal Mixing

In our study, liquid tin (Sn) was mixed with molten polyethylene using an internal mixer; the interfacial tension between the liquid Sn and molten polyethylene was measured using the deformed drop retraction method. The results showed that liquid Sn separated when the Sn content was higher than approximately 2 % by volume because of the interfacial tension of up to 167 mN/m and the 106-fold viscosity difference between the liquid Sn and the molten polyethylene. When Sn separation did not occur, the effects of the mixing time and rotary speed on the degree of mixing and the Sn particle size were analyzed using thermogravimetric analysis and scanning electron microscopy. The results showed that the effects of mixing time and rotary speed on the degree of mixing and Sn particle size can be combined as the impact of specific energy input. With increasing specific energy input, the degree of mixing initially increased and subsequently remained constant, while the Sn particle size initially decreased and subsequently remained constant. The refinement of the dispersed phase was completed with a low specific energy input, but the homogenization of the dispersed phase required a higher specific energy input to achieve completion, revealing the relationship between distributive mixing and dispersive mixing.

Improving electrical conductivity in polycarbonate nanocomposites using highly conductive PEDOT/PSS coated MWCNTs

We describe a strategy to design highly electrically conductive polycarbonate nanocomposites by using multiwalled carbon nanotubes (MWCNTs) coated with a thin layer of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate), a conductive polymer. We found that this coating method improves the electrical properties of the nanocomposites in two ways. First, the coating becomes the main electrical conductive path. Second, the coating promotes the formation of a percolation network at a low filler concentration (0.3 wt %). To tailor the electrical properties of the conductive polymer coating, we used a polar solvent ethylene glycol, and we can tune the final properties of the nanocomposite by controlling the concentrations of the elementary constituents or the intrinsic properties of the conductive polymer coating. This very flexible technique allows for tailoring the properties of the final product.

Nanocomposites of poly(thioureaamide) with carbon nanotube

In the current study, poly(thioureaamide) (PTA) was prepared from isophthaloyl diisothiocyanate and p-phenylenediamine using a facile condensation technique. Fourier transform infrared and proton nuclear magnetic resonance spectroscopic analyses confirmed the structure of the polymer obtained. PTA was then used as a matrix to synthesize organic hybrid materials. In this regard, the functionalized and nonfunctionalized multiwalled carbon nanotubes (CNTs) were utilized as fillers in this work to prepare the nanocomposites. In PTA and functional CNTs system, better compatibility between the organic matrix and the filler was confirmed using field effect scanning electron microscope. The micrographs revealed that the nanotubes were well dispersed in the matrix and packaging of polymer over the surface of functional CNTs. The interaction between polymer chains and functional reinforcement produced mechanical and heat-stable nanocomposites. The tensile strength of the functional CNT-based hybrids 53.21–57.11 MPa was improved as compared with the nonfunctional system (32.79 MPa). The 10% gravimetric loss (513–556°C) and the glass transition temperature of PTA/functional CNTs (184–191°C) depicted a considerable improvement over PTA/nonfunctional CNTs. The results showed the enhanced interactions between the two phases in PTA/functional CNT-based nanocomposites relative to PTA/nonfunctional CNTs.