Dielectric Study of Molecular Mobility in Poly(propylene-graft-maleic anhydride)/Clay Nanocomposites

Abstract

Polymer/clay nanocomposite materials based on poly(propylene-graft-maleic anhydride) (PPgMAH) and two different organophilic modified clays were investigated by dielectric relaxation spectroscopy (DRS). In contrast to ungrafted polypropylene (PP), PPgMAH shows a dielectrically active relaxation process which can be assigned to localized fluctuations of the polar maleic anhydride groups. Its relaxation rate exhibits an unusual temperature dependence, which could be attributed to a redistribution of water molecules in the polymeric matrix. This is confirmed by a combination of Raman spectroscopy and thermogravimetric experiments (TGA) with real-time dielectric measurements under controlled atmospheres. In the nanocomposites this relaxation process is shifted to higher frequencies up to 3 orders of magnitude compared to the unfilled polymer. This indicates a significantly enhanced molecular mobility in the interfacial regions. In the nanocomposite materials a separate high-temperature process due to Maxwell-Wagner-Sillars (MWS) polarization was observed. The time constant of this MWS process can be correlated with characteristic length scales in nanocomposites and therefore provides additional information on dispersion and delamination/exfoliation of clay platelets in these materials. These properties also influence the diffusivity of the water molecules as revealed by real-time dielectric investigations.

Role of surfactant molecular weight on morphology and properties of functionalized graphite oxide filled polypropylene nanocomposites

“…As can be seen form Figure 10a, the dielectric constant, #", of PB/fGO hybrids (at ca. 10 3 ) is much higher than the unfilled matrix (not shown here) due to the interfacial polarization around the exfoliated GO nanoplatlets [46]. Note that the neat matrix maintains a constant #" at 2.2 without dielectrically active relaxation process.…”

“…Figure 11 show the changes of the ac conductivities at 110°C of PB/fGO composites as a function of frequency with the graphite content at 5 wt.%. Note that the ac conductivity ) ac was calculated from #$ with the Equation (1) [46]: ) ac = *·# 0 ·#$ (1) Figure 10. Frequency sweep curves of (a) dielectric permittivity and (b) dielectric loss at 110°C for PB nanocomposites of 5 wt% where * is the angular frequency, # 0 is the absolute permittivity of free space, and #$ is the dielectric loss.…”

Depercolation of aggregates upon polymer grafting in simplified industrial nanocomposites studied with dielectric spectroscopy

“…Polymer in contact with NP surfaces may form immobilized, sometimes referred to as "glassy", layers which are mainly detected by NMR [13,23]. On larger scales, at high temperature (above the glass transition), the occurrence of a Maxwell-Wagner-Sillars (MWS) process has been reported in several composite systems using broadband dielectric spectroscopy (BDS) [21,[24][25][26]. MWS processes are related to polarization effects due to charge carrier diffusion through the different phases of the nanocomposites.…”

Space charge in LLDPE loaded with nanoparticles

“…It has a density of 0.934 g/cm 3 , a melt index of 0.87 g/10 min. Nanoparticles of aluminium oxide from Degussa with a particle size of about 13 nm were used as filler.…”

“…In polymer nanocomposites, chemically dissimilar components are combined at the nanometer scale, and stronger interactions between the polymer and nanoparticles produce markedly improved materials with better electrical, mechanical, thermal, and rheological performances than the conventional filled polymer composites. In recent years, polymer nanocomposites have been extensively studied in optical, thermal and mechanical properties, but there has been relatively little research into dielectric properties [1][2][3][4]. Considering polymers and polymer composites as traditional electrical insulating materials, but with some exceptions, few polymer nanocomposites are used in electrical insulation industry.…”