Validation de la methode par l'etude de liquides aux proprietes connues. Etudes de reseaux covalents obtenus par polycondensation et polyaddition. Analyse par une approche de percolation du comportement elastique haute-frequence du... more
Validation de la methode par l'etude de liquides aux proprietes connues. Etudes de reseaux covalents obtenus par polycondensation et polyaddition. Analyse par une approche de percolation du comportement elastique haute-frequence du polyurethanne. Etude dielectrique de solutions aqueuses de t-butanol pour tenter un rapprochement entre relaxation ultrasonore et dielectrique.
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An application of blocking layers between sample and electrodes permits to avoid the influence of electrode polarization and opens new opportunities in DRS investigations of the conductive systems, such as polysaccharides and proteins... more
An application of blocking layers between sample and electrodes permits to avoid the influence of electrode polarization and opens new opportunities in DRS investigations of the conductive systems, such as polysaccharides and proteins containing water and electrolytes. The proposed methodical approach is applied for plate capacitor type of the cell and for the one in coaxial lien for the measurements in the frequency region 0,1 Hz-10 MHz and 1 MHz-1GHz respectively, using Novocontorl GmbH equipment. The possibilities to investigate an evolution of the biological system in time and temperature scale avoiding the influence of electrode polarization are demonstrated.
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... 3. The excess adiabatic compressibility, 1000 0 101520 35 50 100 ButOH (%) Fig. ... 1 3' ? m 80 - 0 20 3040 50 75 100 0 20 30 4050 75 1( 501 I 0 20 3040 50 75 11 0 0 20304050 75 100 0 2030 4050 75 100 0 2030 4050 75 100 0 203040... more
... 3. The excess adiabatic compressibility, 1000 0 101520 35 50 100 ButOH (%) Fig. ... 1 3' ? m 80 - 0 20 3040 50 75 100 0 20 30 4050 75 1( 501 I 0 20 3040 50 75 11 0 0 20304050 75 100 0 2030 4050 75 100 0 2030 4050 75 100 0 203040 50 75 100 ButOH ("10) Fig. ...
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Previous studies have described an original method enabling the in situ real time monitoring of a composite polymer structure by means of an inserted piezoelectric sensor. An analytical one-dimensional model has demonstrated that the... more
Previous studies have described an original method enabling the in situ real time monitoring of a composite polymer structure by means of an inserted piezoelectric sensor. An analytical one-dimensional model has demonstrated that the electrical impedance of such an inserted element depends in particular on the acoustical parameters of the surrounding media. Then, by solving the inverse problem by means of a nonlinear optimization algorithm, it is possible to determine these acoustical parameters characteristic of the materials in contact with the inserted piezoelectric plate. This technique has been applied to the monitoring of the cure of gel-forming and glass-forming polymers such as polyurethanes and epoxies and compared to classical ultrasonic spectroscopy method. Thus it is possible to detect chemical evolution, transitions, and damage phenomena in such systems, provided that the material is homogeneous in the ultrasonic field or in the area surrounding the piezoelectric elemen...
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Ultrasonic technique is an interesting tool to probe high-frequency dynamic properties of materials by determination of the mechanical modulus. Associated with other methods (rheology, DLS, etc.), it allows the investigation of molecular... more
Ultrasonic technique is an interesting tool to probe high-frequency dynamic properties of materials by determination of the mechanical modulus. Associated with other methods (rheology, DLS, etc.), it allows the investigation of molecular dynamics associated with sol–gel and glass transitions in polymers on a wide frequency range. Polypropylene glycol triol crosslinked with diisocyanate is a good model system for this purpose in polymer networks. By varying the amount of diisocyanate, stable systems are formed which correspond to different stages of polyurethane gel formation. Three triols with different molar masses (260, 700, and 6000 g/mole) are used as precursors in order to apprehend the influence of the macromolecular chain size on the systems dynamics. The temperature dependence of the ultrasonic absorption and velocity shows a relaxation process, the so-called alpha-relaxation associated with the glass transition. The influence of the stoichiometric ratio r=[NCO]/[OH] on this...
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Dielectric Relaxation Spectroscopy (DRS) has been applied for the investigation of the influence of the metal/polymer interfacial interaction on the dielectric relaxation properties of polyurethane (PU), in the frequency range from 0,1 Hz... more
Dielectric Relaxation Spectroscopy (DRS) has been applied for the investigation of the influence of the metal/polymer interfacial interaction on the dielectric relaxation properties of polyurethane (PU), in the frequency range from 0,1 Hz to 10 MHz at temperatures from 223 to 423 K in the dependence of thickness of the PU layer (from 10 to 150 μm) and electrode material (gold and steel). Strong electrostatic interaction between steel substrate and the PU results in changing the dielectric relaxation properties of the latter, comparatively with gold substrate. The influence of metal/polymer electric double layer becomes significant at thickness less than 60 μm for the steel substrate. For the gold electrodes, the relaxation characteristics of the PU hardly depend on thickness.
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Composites having ceramic LiSn2P3O12 particles, that are Li+ ion conductor, and Teflon, that is an insulating polymer and works as binder, have been prepared in a wide compositional range (from 8 to 74% by volume of LiSn2P3O12). Their... more
Composites having ceramic LiSn2P3O12 particles, that are Li+ ion conductor, and Teflon, that is an insulating polymer and works as binder, have been prepared in a wide compositional range (from 8 to 74% by volume of LiSn2P3O12). Their microstructure, as followed by Scanning Electron Microscopy, has been analyzed to understand the aggregation process of the ceramic particles. For low LiSn2P3O12
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Silver nanoparticles with size less than 50 nm were synthesized from silver nitrate, polyvinylpyrrolidone (PVP) and ethylene glycol, where these chemicals acted as metal precursor, stabilizer and reducing agent, respectively. Then a... more
Silver nanoparticles with size less than 50 nm were synthesized from silver nitrate, polyvinylpyrrolidone (PVP) and ethylene glycol, where these chemicals acted as metal precursor, stabilizer and reducing agent, respectively. Then a conductive silver ink was prepared with a suitable solvent by adding a viscosifier, hydroxyethyl-cellulose (HEC), and a surfactant, diethylene glycol (DEG). The combined effect of both viscosifier and surfactant on the physical property of the silver ink was analyzed by measuring the contact angle of the silver ink on a cellulose film. Moreover, the influences of PVP molecular weight and reaction temperature on the size of the silver nanoparticles were analyzed. Then the silver ink was coated on the cellulose film by spin coating and the effects of different solvents, sintering temperatures and solid contents on its electrical resistivity were examined. It was found that, with 50 % co-solvent of deionized water and DEG and solid content of around 50 %, the silver ink exhibited the lowest resistivity. This ink can be used for inkjet printing of conductive patterns on cellulose films.
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– Electrical conductive fibers (e.g., carbon fibers) provide the possibility to establish in polymer materials electrical conductivity and good mechanical properties simultaneously. The fibers orientation and length, their volume fraction... more
– Electrical conductive fibers (e.g., carbon fibers) provide the possibility to establish in polymer materials electrical conductivity and good mechanical properties simultaneously. The fibers orientation and length, their volume fraction and the fiber matrix adhesion can influence the electrical conductivity of the fiber composites [1]. Three-dimensional simulations have been conducted to predict percolation threshold in fiber composite materials. A method is proposed to evaluate electrical resistance of fibrous composites. Assuming meandering paths, calculation is based on detecting conductive pathways through the insulating matrix. Percolation is detected by the height of the conducting cluster instead of its number at the two electrodes. The electrical resistivity and the conduction thresholds of the carbon fiber reinforced polycarbonate composites have been characterized. Decreasing the percolation threshold with longer fiber has been verified. Lower conduction thresholds are o...
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Parmi les conducteurs organiques, la polyaniline (PANI) est le polymere qui presente une grande stabilite environnementale et une grande conductivite electrique. Cependant, elle presente egalement des inconvenients tels que ses faibles... more
Parmi les conducteurs organiques, la polyaniline (PANI) est le polymere qui presente une grande stabilite environnementale et une grande conductivite electrique. Cependant, elle presente egalement des inconvenients tels que ses faibles proprietes mecaniques qui representent un verrou technologique pour de nombreuses applications. Pour y remedier, une des methodes consiste a les associer avec des polymeres conventionnels pour former des composites ayant a la fois les proprietes mecaniques de la matrice et les proprietes electriques de PANI. Aussi, deux types de composites conducteurs a base de PANI et de polyamide (PA) ont ete elabores: les films composites conducteurs en surface et les composites conducteurs en volume sous forme de poudres et de films. La synthese rationnelle et la conception de ces materiaux necessitent l'etablissement de relation synthese-structure-proprietes. L'etude electrochimique et chimique a montre que la vitesse de polymerisation de l'aniline es...
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The present work deals with the preparation of films from polymeric core-shell particles. Our approach is based on the chemical polymerization of a very thin layer of polyaniline (PANI) around particles of transparent polymers (polyamide... more
The present work deals with the preparation of films from polymeric core-shell particles. Our approach is based on the chemical polymerization of a very thin layer of polyaniline (PANI) around particles of transparent polymers (polyamide and polystyrene). Films are then obtained by dissolving the two type synthesized core-shell powders in dichloromethane and m-Cresol respectively. Electrical properties were investigated using a dielectric relaxation spectrometer. Both composite films exhibited a percolative behaviour and a well established dc conductivity for high PANI concentration related to the conductive properties of the PANI spanning clusters. This property allows using such films in semi-conductive applications. For polyamide films, high dielectric constants were obtained at 5 wt. % of PANI allowing their use as high k-dielectrics compatibles with organic printed circuit boards.
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Surface conductive composites for antistatic purposes consisting of polyamide 6 (PA‐6) polymer films as a matrix containing conductive polyaniline (PANI) particles were chemically elaborated at room temperature by in situ polymerization... more
Surface conductive composites for antistatic purposes consisting of polyamide 6 (PA‐6) polymer films as a matrix containing conductive polyaniline (PANI) particles were chemically elaborated at room temperature by in situ polymerization of aniline inside the matrix. These kind of Polyamide/PANI composites were investigated regarding to their microstuctural and electrical properties. The surface conductivity was characterized using the potential decay technique. The results were correlated with scanning electron microscopic images data concerning PANI particles dispersion in these antistatic polymer films (ASPF). The enhanced surface conductivity was due to percolation of the PANI phase in the surface layer of PA‐6 films. It has been shown by X ray spectra that the crystallinity of the films is also enhanced. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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Summary: Volume conducting PA‐12 based composites powders were chemically prepared by in situ polymerization and aniline doping at room temperature. These kinds of polyamide / PANI composites were investigated regarding their electrical... more
Summary: Volume conducting PA‐12 based composites powders were chemically prepared by in situ polymerization and aniline doping at room temperature. These kinds of polyamide / PANI composites were investigated regarding their electrical properties. Their ac and dc electrical properties measured in the frequency range of 10−2–107 Hz are reported and the frequency dependence of electrical conductivity was investigated as a function of PANI concentration leading to the determination of the conductivity. The experimental conductivity was found to increase continuously with PANI content and explained by percolation theory with a relatively low percolation threshold of about 0.4 wt.%. The dielectric behavior of various PANI polymer composites has been characterized by the critical frequency ωc (denoting the crossover from the dc plateau of the conductivity to its frequency dependent ac behaviour). Modelling the conductivity behavior versus volume fraction using Slupkowski approach has rev...