Comparing the elasticity of the melt and electrical conductivity of the solid of PP-HDPE copolymer CNT composites obtained by direct compounding versus dilution of a PP masterbatch

Abstract

Composites of multiwall carbon nanotubes (CNT) at 1, 2, and 3 wt.% on a polypropylene–polyethylene random copolymer matrix were prepared by melt compounding CNT powder and by dilution of a commercial polypropylene masterbatch (PMB). While the shear viscosity shows similar behavior for both dilution modes, the differences in their elastic properties clearly show the effect of the addition method and the presence of the PMB. This also indicates the relevance of having a difficult to mix masterbatch to enhance the elongational viscosity of the composites for free wall applications such as fiber spinning and blown film. On the other hand, the 2 and 3 wt.% CNT composites from both addition modes have similar electrical conductive behavior, with values near the semiconductors’ range. TEM and SEM images show different states of dispersion for each source of CNT. The immiscibility observed in those images is the simplest explanation for the differences in the molten composites’ elastic properties due to direct CNT addition versus CNT addition by dilution of a PMB.

PVDF Hybrid Nanocomposites with Graphene and Carbon Nanotubes and Their Thermoresistive and Joule Heating Properties

“…A schematic illustration is presented in Figure 7 . In addition, the percolation threshold of the MWCNTs (Nanocyl NC7000) was reported to be around 2 wt.% [ 41 ]. In the 4.5% GNP/1.5% CNT–PVDF composition, the content of the MWCNTs was just before the percolation occurred.…”

“…Researchers reported [ 43 ] that amorphous regions in semi-crystalline polymers tend to have higher thermal expansion than do crystalline regions. Thus, the lowest crystallinity of the 4.5% GNP–1.5% CNT–PVDF composite ( Table 3 ), compared to the neat PVDF and the other nanocomposites, confirmed the highest sensitivity to thermal expansion of this hybrid composite, which may provoke the disruption of the weak percolated structure of MWCNTs around the percolation threshold, that is, 1–2 wt.% for the extrusion-processed polymer composites [ 28 , 41 ].…”

“…According to the datasheet in [42], the coefficient of linear thermal expansion (CLTE) of the homopolymer PVDF Kynar 700 series as a function of temperature is 14 × 10 −5 /°C at According to the datasheet in [42], the coefficient of linear thermal expansion (CLTE) of the homopolymer PVDF Kynar 700 series as a function of temperature is 14 × 10 Researchers reported [43] that amorphous regions in semi-crystalline polymers tend to have higher thermal expansion than do crystalline regions. Thus, the lowest crystallinity of the 4.5% GNP-1.5% CNT-PVDF composite (Table 3), compared to the neat PVDF and the other nanocomposites, confirmed the highest sensitivity to thermal expansion of this hybrid composite, which may provoke the disruption of the weak percolated structure of MWCNTs around the percolation threshold, that is, 1-2 wt.% for the extrusion-processed polymer composites [28,41].…”

Development of electrically conductive polymer nanocomposites for the automotive cable industry

“…Several studies reported the mechanical and electrical properties of nanocomposites containing CNT. For example, the addition of 1, 2 and 3 wt.% of CNT by melt compounding with a polypropylene (PP) copolymer through the dilution of a masterbatch containing 20 wt.% of CNT, and the comparison with direct compounding of 1, 2 and 3 wt.% CNT into PP, was investigated [29] . An increase in electrical conductivity was obtained by both methods, however due to poorer dispersion of CNT achieved by masterbatch dilution, these composites showed comparitively lower conductivity than those produced by direct CNT compounding into the PP matrix.…”