Isotactic polypropylene–vapor grown carbon nanofibers composites: Electrical properties

Abstract

Nanocomposites have been obtained by dispersing various amounts of vapor grown carbon nanofibers within isotactic polypropylene. Thermal investigations done by differential scanning calorimetry and dynamic mechanical analysis revealed the effect of the vapor grown carbon nanofibers on the melting, crystallization, α, and β relaxations. Direct current electrical features of these nanocomposites have been investigated and related to the thermal features of these nanocomposites. The effect of the loading with carbon nanofibers on the electrical properties of these nanocomposites is discussed within the percolation theory. The percolation threshold was estimated at about 5.5% wt carbon nanofibers. The temperature dependence of the direct current conductivity is analyzed in detail and it is concluded that the electronic hopping is the dominant transport mechanism. A transition from one‐dimensional hopping towards a three‐dimensional hopping was noticed as the concentration of carbon nanofibers was increased from 10% wt to 20% wt carbon nanofiber. The possibility of a differential negative resistivity is suggested. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45297.

Electrical properties of melt-mixed polypropylene and as-grown carbon nanofiber composites: Analysis of their interphase via the AC conductivity modeling

“…ΔH m is the sample melting enthalpy and ΔH 0 f PP is the melting enthalpy of the 100% crystalline PP (207 J g À1 ). 28 The PP showed a single melting peak at ∼ 166°C in accordance with other works that report melt-compounding PP-based composites , 23 whereas a slight decrease in the melting temperature is noticed for the PP/CNF composites in Figure 4(b). Notably, the results in Figure 4(b) show a clear increase of ΔX c ∼ 15% with respect to the PP (∼34%) for PP/CNF composites with 1.4 vol.…”

“…The latter result has been associated to the degree of stretching rise of the macromolecular polymer chains caused by the loading with the nanoparticles. 23…”

“…22 It is noted that this particular CNF grade is synthesized in as-grown condition without the utilization of any postprocessing method. Morphologically, the CNFs show hollow core diameters in the range of 30–90 nm, total diameters of 100–200 nm, and lengths of 30–100 μm, 22,23 with conductivities of 10 3 S m −1 . 23…”

“…Morphologically, the CNFs show hollow core diameters in the range of 30–90 nm, total diameters of 100–200 nm, and lengths of 30–100 μm, 22,23 with conductivities of 10 3 S m −1 . 23…”

Electrical Properties of Polypropylene-Based Composites Melt-Processed with As-Grown Carbon Nanofibers

“…On the other hand, vapor grown carbon nanofibers (CNFs) are an attractive option among other carbon materials, such as carbon black (CB), carbon nanotubes (CNTs), and graphene, as reinforcing fillers for polypropylene given their large surface area, high strength and storage modulus, and excellent thermal and electrical properties [5]. This type of CNF, which is produced by chemical vapor deposition (CVD) of catalyst nanoparticles under a mixture of gaseous hydrocarbons [6], have tubular hollow cores surrounded by ordered inner stacked-cup and disordered outer layers, with lengths and diameters ranging from 50 to 100 μm, and 50 to 200 nm, respectively [7,8]. In particular, due to their remarkably electrical conductivities (10 4 Sm À1 ), the production of conductive PP composites based on CNFs by melt-mixing has been the subject of investigation during the past few decades [9][10][11].…”