The effective complex permittivity stability in filled polymer nanocomposites studied above the glass transition temperature

Abstract

The temperature effecton the dielectric response of nanocomposite at low frequencies range is reported. The investigated samples are formed by a semi-crystalline ethylene-co-butyl acrylate (EBA) polymer filled with three concentrations of the dispersed conducting carbon black (CB) nanoparticles. The temperature dependence of the complex permittivity has been analyzedabove the glass transition temperature of the neat polymer matrix Tg=-75°C. For all CB concentrations, the dielectric spectra follow a same trend in frequency range 100-106Hz. More interestingly, the stability of the effective complex permittivity ɛ=ɛ' -iɛ'' with the temperature range of 10-70°C is explored. While the imaginary part of the complex permittivity ɛ'' exhibits a slight decreasewith temperature, the real part ɛ' shows a significant reduction especially for high loading samples. The observed dielectric response may be related to the breakup of the three-dimensional structurenetwork formed by the aggregation of CB particles causing change at the interfaceEBA-CB.This interface is estimated bythe volume fraction of constrained polymer chain according to loss tangent data of dynamic mechanical analysis.

Nano‐indentation for probing mechanical properties of nanocomposites based on ethylene butyl acrylate copolymer and carbon black

“…Moreover, the increase of CB concentration leads to a large increase of the stiffness and to a reduction of the toughness . It is to be noticed that the lower deviation of H / E values for highly loaded composite samples indicates a good dispersion of CB throughout the polymer matrix confirming the same conclusions reported in our previous studies by using dielectric and mechanical analyses.…”

The effective complex permittivity stability in filled polymer nanocomposites studied above the glass transition temperature

“…This trend is obvious sincethe density of CB/EBA interfaces increases by adding more CB amount. In fact, theattractive interactions between fillers and polymer result in a socalled constrained layer [13]. The volume fraction of constrained polymer chain  can be estimated according to the dynamic mechanical analysis (DMA) [13].The  values that are 0.342, 0.375 and0.422 are found to increasewith the three CB concentrations 6.8, 15.8 and 19.9%.Secondly, we observea slight decrease of the imaginary part   with temperature for all composites samples as can be seen in Figures 3.…”

“…In fact, theattractive interactions between fillers and polymer result in a socalled constrained layer [13]. The volume fraction of constrained polymer chain  can be estimated according to the dynamic mechanical analysis (DMA) [13].The  values that are 0.342, 0.375 and0.422 are found to increasewith the three CB concentrations 6.8, 15.8 and 19.9%.Secondly, we observea slight decrease of the imaginary part   with temperature for all composites samples as can be seen in Figures 3. This behavior agree with the result reported in the Ref 9 concerning the dc electrical conductivity versus temperature and is attributed to the thermal expansion coefficient (TEC) of the matrix which is larger than that of the CB [14,15].Thermal expansion resulting from temperature increase causes greater separation between the CB particles and hence leading to a decrease of losses.However, the real part   behaves differently with temperature.…”