Influence of shear-induced crystallization on the electrical conductivity of high density polyethylene carbon nanotube nanocomposites

Abstract

Abstract:The relation between shear mixing time in the melt, polymer crystal size, and electrical conductivity is studied for high density polyethylene -carbon nanotubes nanocomposites with 2 the help of in-situ rheo-dielectric and rheo-small angle synchrotron X-ray scattering (SAXS) techniques. Results show that the memory of crystal structure obtained after melt-mixing is not easily removed by re-melting and annealing. The conductivity of composites shear-mixed for 20 min. cannot reach that of 10 min. samples, even after additional quiescent annealing for 6000 s at 190 o C. The rheo-SAXS data further indicate that the temperature needed to melt all the crystals is higher for the longer time shear mixed composites. These results all suggest that with long processing time, larger crystals are nucleated and grow on the nanotubes, which reduce electrical conductivity, presumably because they prevent electrical contact between the nanotubes.

Electrically conducting polymer nanostructures confined in anodized aluminum oxide templates (AAO)

“…These results agree with others reported in the literature [50]. For instance Tao et al [51] also reported a decrease in conductivity with temperature for a composite of MWCNTs and polyethylene at higher temperatures (T > T m ) and was related to the phenomena of crystallization of polyethylene which would disconnect the conductive paths [51]. Other authors [40,52] also observed a continuous increase of conductivity with temperature below T m (positive temperature coefficient effect of the resistivity).…”

Effect of processing conditions on the structure, electrical and mechanical properties of melt mixed high density polyethylene/multi-walled CNT composites in compression molding

“…It can be observed in Figure 7 that the nanocomposite containing 2 wt% MWCNTs under RC exhibits a slightly higher maximum current of 20.77 nA and more conductive regions uniformly distributed in the matrix compared to that under SC, indicating more conductive networks formed. This may be due to the lower crystallinity and smaller crystallites at RC facilitating the formation of conductive pathways [21] [40]. The information on the crystallinity and crystallite sizes of HDPE/MWCNT nanocomposites was presented via the XRD and DSC results in the previous section (Table 2).…”

“…In the past few years, the dispersion, structure and properties of melt mixed HDPE/CNT nanocomposites have been extensively discussed in previous literature [18] [19] [20] [21]. Morcom et al [18] investigated the dispersion and reinforcing effect of multi-walled carbon nanotubes (MWCNTs) on the properties of a melt mixed HDPE/MWCNT composite.…”

“…Yang's [20] investigation of injection moulding of HDPE/MWCNT nanocomposites showed that MWCNTs nucleated HDPE crystal growth and induced a special transcrystalline microstructure (shish-kebab crystal) in a dynamic packing injection moulding (DPIM) process. Tao et al [21] investigated the effect of shear-induced crystallization on the electrical properties of melt mixed HDPE/MWCNT composites. A similar transcrystalline structure to that observed in Yang's study [20] was also observed.…”

Preparation and comparative properties of membranes based on PANI and three inorganic fillers

“…Incorporating inorganic nanoparticles into organic polymers will improve the mechanical, thermal, optical and barrier properties. Commonly used inorganic additives include clay [1,2], SiO 2 [3][4][5], carbon nanotubes [6,7], and carbon nanofibers [8], among others. Polyaniline (PANI) is a potential material for commercial applications owing to its facile synthesis, relatively low cost, environmental stability, good processability, and unique optical, electrical and electrochemical properties [9,10].…”