In this paper, the electrical and thermal conductivity and morphological behavior of low density polyethylene (LDPE)/multi-walled carbon nanotubes (MWCNTs) + graphene nanoplatelets (GNPs) hybrid nanocomposites (HNCs) have been studied. The distribution of MWCNTs and the hybrid of MWCNTs/GNPs within the polymer matrix has been investigated with scanning electron microscopy (SEM). The results showed that the thermal and electrical conductivity of the LDPE-based nanocomposites increased along with the increasing content of carbon nanofillers. However, one could observe greater improvement in the thermal and electrical conductivity when only MWCNTs have been incorporated. Moreover, the improvement in tensile properties and thermal stability has been observed when carbon nanofillers have been mixed with LDPE. At the same time, the increasing content of MWCNTs and MWCNTs/GNPs caused an increase in the melt viscosity with only little effect on phase transition temperatures.

Poly(trimethylene terephthalate) nanocomposites containing COOH functionalized multi-walled nanotubes were synthesized with in situ polymerization method. The microstructure of the nanocomposites was studied by SEM, in terms of the dispersion state of the nanotubes and the polymer–nanotube interface. The thermal behaviour, mechanical properties and conductivity of these resultant PTT/MWCNTs nanocomposites were studied. The effect of the presence of MWCNTs on cold crystallization of PTT was monitored by dielectric spectroscopy. From thermal analysis study, it is found that the melting temperature and glass transition temperature are not significantly affected by the addition of MWCNTs. The crystallization temperature of PTT matrix is affected by the presence of CNTs. Nanocomposites have slightly higher degree of crystallinity than neat PTT and their thermo-oxidative stability is not significantly affected by the addition of MWCNTs. The study of the isothermal cold crystallization of amorphous PTT and its nanocomposites monitored by dielectric spectroscopy reveals that the presence of MWCNTs have influence on crystallization rate, especially at higher concentration (0.3 wt%). In comparison with neat PTT, the MWCNTs reinforced nanocomposites posses higher tensile strength and Young’s modulus at low MWCNTs loading (0.05–0.3 wt%). In addition, all nanocomposites show reduction of brittleness as compared to the neat PTT. The electrical percolation threshold was found between 0.3 and 0.4 wt% loading of MWCNTs

No abstract

Poly(trimethylene terephthalate) (PTT) composites filled with well-dispersed functionalized multi-walled carbon nanotubes (MWCNT-COOH) and graphene nanosheets (GNS) were prepared through in situ polymerization. The effect of increased nanotubes and nanosheets concentration on the electrical conductivity and rheological behavior was investigated. The electrical conductivity increased by about ten orders of magnitude for PTT/MWCNT-COOH/GNS composites with 0.4 wt% of MWCNT-COOH and 0.3 wt% of GNS content. For insulating hybrid polymer nanocomposites, with a MWCNT-COOH content £ 0.2 wt%, GNS produces a synergic effect by acting as junction additive for MWCNT leading to additional conductive pathways. However, for hybrid nanocomposites with 0.4 wt% of MWCNT-COOH further addition of GNS caused only slight improvement in electrical conductivity. Additionally, rheological analysis confirmed interconnected or network-like structures formed as a result of nanofiller-nanofiller and nanofiller-polymer interactions.POLYM. COMPOS., 00:000-000, 2017. FIG. 2. TEM images of PTT nanocomposites containing: (a) 0.2 MWCNT-COOH, (b) 0.2 wt% of MWCNT-COOH 1 0.05 wt% GNS, and (c) 0.2 wt% of MWCNT-COOH 1 0.1 wt GNS%. FIG. 3. TEM images of PTT nanocomposites containing: (a) 0.4 MWCNT-COOH, (b) 0.4 wt% of MWCNT-COOH 1 0.1 wt% GNS, and (c) 0.4 wt% of MWCNT-COOH 1 0.3 wt GNS%.

The research was planned to test electrical properties of polymer films made from polyurethane cationomers with 0–2 wt.% graphene admixture. The cationomers were synthetized in the reaction of 4,4′-methylenebis(phenyl isocyanate), polycaprolactone diol (M = 2000), N-methyldiethanolamine, and formic acid. It was found that addition of approx. 2 wt.% of graphene causes the loss of volume resistivity by three orders of magnitude and percolation threshold is already set at approx. 1 wt.%. The frequency characteristic of a real part of permittivity ε′ and imaginary part of permittivity ε″ were measured for the tested films. On the base of Havriliak–Negami equation, parameters of relaxation functions in frequency domain were estimated for samples containing various contents of graphene. The influence of the cationomer phase structure on observed changes of dielectric losses coefficient tgδ in the full-measuring frequency spectrum was discussed.