Filler reaggregation and network formation time scale in extruded high‐density polyethylene/multiwalled carbon nanotube composites

Abstract

A high‐density polyethylene (HDPE) masterbatch containing 20.2 wt% multiwalled carbon nanotubes (MWNTs) was melt diluted with neat HDPE using two different methods: a twin screw microcompounder and a single‐screw extruder. The electrical properties of these composites were assessed using bulk electrical conductivity measurements, their mechanical properties were evaluated using tensile tests and dynamic mechanical analysis (DMA), and percent crystallinity was determined by wide angle x‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). A percolation threshold (pc) of 4.5 wt% MWNTs was found in compression‐molded samples. Extruded samples were prepared with nanotube concentrations below and above the compression‐molded percolation threshold (2 and 7 wt% MWNTs) and passed through the extruder twice before entering a low‐shear melt annealing zone. Different melt annealing times were used and their effects on the electrical and mechanical properties of the resulting quench‐cooled composites were evaluated. Results showed that extruded composites were nonconductive, indicating that a conductive nanotube network did not form on the time scale of these experiments. Annealing time also did not affect significantly the mechanical properties of the resulting solid composites. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Electrical, mechanical, and crystallization properties of ethylene‐tetrafluoroethylene copolymer/multiwalled carbon nanotube composites

“…35,36 Within the ability to distinguish shifts in peak position, no changes in the peak position occurred with the addition of nanotubes and hence the long spacing was also unchanged. The same invariance to the long spacing with the addition of nanotubes has also been found for high-density polyethylene 37 although changes were found for polypropylene 38 as well as for poly(ethylene oxide) with surfactant-stabilized nanotubes. 39 Figure 9 shows representative optical micrographs for selected nanotube contents, and Figure 10 shows the statistical distribution of the sizes based on circle-equivalent diameters using micrographs of the type shown in Figure 9.…”

“…Within the ability to distinguish shifts in peak position, no changes in the peak position occurred with the addition of nanotubes and hence the long spacing was also unchanged. The same invariance to the long spacing with the addition of nanotubes has also been found for high‐density polyethylene although changes were found for polypropylene as well as for poly(ethylene oxide) with surfactant‐stabilized nanotubes …”

Effect of carbon nanotube dispersion and network formation on thermal conductivity of thermoplastic polyurethane/carbon nanotube nanocomposites

“…Potential drawbacks of ultrasonication are CNT breakage and media degradation due the high energy delivered to the samples during sonication . For CNT dispersion in higher viscosity systems such as low molecular weight polyols and epoxy resins, the calendaring process is the method of choice , while in the case of high viscosity polymer melts, mixing in twin screw extruders and internal mixers is employed .…”

Thermal, mechanical, and tribological properties of epoxy polymer/EPU blends reinforced by low concentration of octaaminophenyl POSS

“…In recent years, improving the toughness of epoxy resin without sacrificing its thermal stability and abrasion resistance has become an important research issue [3][4][5]. Therefore, various additives and/or combinations from polymers to inorganic materials have been used to modify epoxy polymer, including liquid rubber, thermoplastic resin, nanoSiO 2 , layer silicate, carbon nanotubes, graphene, and POSS [6][7][8][9].…”