Influence of processing conditions on nanoindentation properties of spark plasma sintered ptfe

The Spark Plasma Sintering (SPS) is considered as fast sintering route using self-heating action from inside the powder similar to microwave sintering and self-propagating high temperature. High sintering rate, low temperature processing, ease of operation and accurate control of sintering energy are the major advantages of this non-melting technique with regard to classical methods. The aim of this investigation is to take benefit from the advantages offered by the SPS process in order to sinter the polytetrafluoroethylene (PTFE) polymer materials from PTFE powder particles. The effect of the process’s parameters, namely the sintering temperature and heating rate, on the nanoindentation deformation is explored at room temperature. Empirical data on depth-dependent hardness are confronted to some theoretical models with a special focus on the apparent surface stress changes with the indentation depth. Furthermore, the obtained results are compared to the macro-behavior deduced from tensile and bending properties in order to assess the change in both surface and bulk deformations of the SPSed samples and according to the processing parameters

Nanoindentation hardness and macroscopic mechanical behaviors in filled elastomeric nanocomposites

Carbon black (CB) filled semi-crystalline ethylene butyl acrylate (EBA) copolymer networks are investigated to probe for the CB particles dependence of the deformation behavior from nano-to micrometers length scales of samples which are submitted to nanoindentation characterization. With respect to this purpose, the phenomenology for hardness (H) response in these materials indicates a typical increase of the hardness by decreasing the indentation depth (h) similar to the observed behavior in elastomeric materials. This behavior can be related to the change of the mesostructure, formed by the heterogeneous three-dimensional interconnected network of polymer and of aggregates of CB particles. Furthermore, The CB amount is found to increase the resistance of composite under the action of a mechanical stress. The H-h curves were then compared to some analytical models and correlated to a tensile macroscopic behavior in order to highlight the involved deformation mechanisms with length scale. A complementary set of characterizations such as profilometry and atomic force microscopy probes were also employed to best understand of those mechanisms

Nanoindentation hardness and macroscopic mechanical behaviors in filled elastomeric nanocomposites

Carbon black (CB) filled semi-crystalline ethylene butyl acrylate (EBA) copolymer networks are investigated to probe for the CB particles dependence of the deformation behavior from nano-to micrometers length scales of samples which are submitted to nanoindentation characterization. With respect to this purpose, the phenomenology for hardness (H) response in these materials indicates a typical increase of the hardness by decreasing the indentation depth (h) similar to the observed behavior in elastomeric materials. This behavior can be related to the change of the mesostructure, formed by the heterogeneous three-dimensional interconnected network of polymer and of aggregates of CB particles. Furthermore, The CB amount is found to increase the resistance of composite under the action of a mechanical stress. The H-h curves were then compared to some analytical models and correlated to a tensile macroscopic behavior in order to highlight the involved deformation mechanisms with length scale. A complementary set of characterizations such as profilometry and atomic force microscopy probes were also employed to best understand of those mechanisms

Electronic conduction and microstructure in polymer composites filled with carbonaceous particles.

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Assessing robustness of hyperelastic models for describing nonlinearity of the mechanical response for pristine and swollen carbon black filled elastomers

International audienceWe consider the hyperelastic response of semi-crystalline ethylene-co-butyl acrylate (EBA) samples filled with carbon black (CB) particles. Such material is structurally complex with its microstructure being characterized by many structural parameters including crosslink density, filler/matrix interfaces, crystallinity, filler network, and chain entanglement which have different degrees of influence on the effective mechanical properties. We evaluate the ability of a number of analytical models to correctly reproduce the non-linear elastic mechanical response of these samples. We do this by considering either dry samples, or samples which are swollen by a non-polar solvent (toluene) at equilibrium, and subjected to uniaxial tension at room temperature. As test cases, we focus on six physical models for the purpose of analyzing the stress-strain curves of samples with different cross-linking densities. Among these frameworks, we show that the Mooney-Rivlin (MR), Ogden, and eight-chain models accurately describe the stress-strain curves of both dry and swollen CB-EBA samples. These findings highlight the possibility of attaining a diverse set of mechanical properties of filled polymer samples by tailoring their structural parameters.</div

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

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

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

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

Influence of processing conditions on nanoindentation properties of spark plasma sintered PTFE

The Spark Plasma Sintering (SPS) is considered as fast sintering route using self-heating action from inside the powder similar to microwave sintering and self-propagating high temperature. High sintering rate, low temperature processing, ease of operation and accurate control of sintering energy are the major advantages of this non-melting technique with regard to classical methods. The aim of this investigation is to take benefit from the advantages offered by the SPS process in order to sinter the polytetrafluoroethylene (PTFE) polymer materials from PTFE powder particles. The effect of the process’s parameters, namely the sintering temperature and heating rate, on the nanoindentation deformation is explored at room temperature. Empirical data on depth-dependent hardness are confronted to some theoretical models with a special focus on the apparent surface stress changes with the indentation depth. Furthermore, the obtained results are compared to the macro-behavior deduced from tensile and bending properties in order to assess the change in both surface and bulk deformations of the SPSed samples and according to the processing parameters

THE SPARK PLASMA SINTERING (SPS) AS A HIGH RAPID AND EFICIENT METHOD TO ELABORETE DENSE MATERIALS: APPLICATION FOR HIGH VISCOUS POLYMER

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