Morphology and electrical properties of short carbon fiber-filled polymer blends: High-density polyethylene/poly(methyl methacrylate)

Abstract

Morphology and electrical properties of short carbon fiber-filled high-density polyethylene (HDPE)/poly(methyl methacrylate)(PMMA) polymer blends have been studied. The percolation threshold of HDPE50/PMMA50 blends filled with vaporgrown carbon fiber (VGCF), 1.25 phr VGCF content, is much lower than those of the individual polymers. The SEM micrographs verified that the enhancement of conductivity could be attributed to the selective location of VGCF in the HDPE phase. A double percolation is the basic requirement for the conductivity of the composites, i.e., the percolation of carbon fibers in the HDPE phase and the continuity of this phase in the blends, which hereby are defined as the first percolation and the second percolation, respectively. The SEM micrographs also showed that the short carbon fibers could affect the morphology of the blends. With the increase of VGCF content, the HDPE domains are elongated from spherical into strip shape, finally develop to a continuous structure. As a result, the second percolation threshold of the blends filled with 2.5 phr VGCF, 20 wt % HDPE, is lower than that of the blends filled with 1.5 phr VGCF, 30 wt % HDPE. The influence of molding temperature and time on the second percolation threshold has also been investigated. For the composites molded at a lower temperature, the second percolation threshold is shifted to a higher VGCF content, but there is little influence of molding time on the second percolation threshold.

On the phase affinity of multi-walled carbon nanotubes in PMMA:LDPE immiscible polymer blends

“…Similar behavior has been reported elsewhere [21] for an equiviscous PP/PS blend. Even though the melt-state linear rheology of PMMA/LDPE blends has not been studied in depth before, the limits of co-continuity and phase inversion concentration herein reported match fairly well with the results obtained by selective solvent extraction on PMMA/HDPE blends conducted by Cheng Zhang et al [14]. The mixing time affects the domain of co-continuity, in such a way that if it is very long the co-continuity range will tend to a single composition [22].…”

“…Moreover, electrical resistivity values later shown in Figure 4A will prove that pure PMMA becomes semiconductive with addition of 2 wt.% MWCNTs whereas, at such a concentration, LDPE retains its insulating properties. Some researches claim to have found lower electrical percolation threshold for LDPE or HDPE than for PMMA [7,14]. However, in both of these studies compounding was conducted at constant temperatures (190 and 210 ºC, respectively), which is not the case in our study (220 ºC for PMMA and 180 ºC for LDPE).…”

“…carbon black, fibers or nanotubes). The published data is mainly composed of morphological characterization based on SEM/TEM observations which the authors use to justify electrical conductivity results based on double percolation theory or to try to reduce the electrical percolation threshold [9,10,13,14]. Moreover, very little attention has been paid to the linear viscoelasticity behaviour of these CNT filled blends.…”

Transparent Conductive Films Fabricated from Polythiophene Nanofibers Composited with Conventional Polymers

“…On the other hand, conductive nanofiller/polymer composite materials have attracted great academic and industrial attention, as they offer high conductivity in a conventional flexible polymeric film [13][14][15][16][17], and various new materials have been developed to satisfy market needs, exhibiting for example, specific thermal [18][19][20][21][22][23][24][25], mechanical [26,27], and electrochemical properties [28−36] in addition to conductivity. There are several different types of conductive nanofillers, including carbon nanotubes [18][19][20][21][22][23][24][28][29][30][31][32][33][34][35][36], carbon fibers [26], metal particles [25], and conductive polymers [37,38].…”

“…There are several different types of conductive nanofillers, including carbon nanotubes [18][19][20][21][22][23][24][28][29][30][31][32][33][34][35][36], carbon fibers [26], metal particles [25], and conductive polymers [37,38]. Our aim in the present work was to solve the problems associated with the P3HT nanofiber mat as a transparent, conductive film by using the nanocomposite technique.…”