Papers by Colette Lacabanne
Journal of Applied Polymer Science, 2019
This study is devoted to the analysis of the properties of continuous bamboo fiber (BF)-reinforce... more This study is devoted to the analysis of the properties of continuous bamboo fiber (BF)-reinforced polyamide 11 (PA 11) composites. The SEM observations highlighted continuity between BFs and the polymeric matrix showing a high density of hydrogen bonds. The comparative calorimetric study of the matrix and its composites showed that the crystallinity of PA 11 was not modified by the presence of bamboo fibers. The physical aging observed in PA 11 is no more observed in composites due to physical interactions between PA 11 and BFs. The mechanical properties were investigated by tensile strength and dynamic mechanical analysis. The introduction of BFs enhanced Young's modulus of the matrix by a factor of 10. The presence of BFs also improved the storage shear modulus G 0 over the whole temperature range.
Thermally stimulated current and dielectric relaxation of inorganic/organic ferroelectric nanocomposites
2008 13th International Symposium on Electrets, 2008
PA11/BaTiO3 nanocomposites were elaborated with various particles size. These samples were poled ... more PA11/BaTiO3 nanocomposites were elaborated with various particles size. These samples were poled under low field to elaborate poled ceramic/unpoled polymer composite. We found that the piezoelectric coefficient is highly poling temperature and poling time dependent. By poling the samples above the glass transition of the matrix, the piezoelectric coefficient of the composite were performed. The maximum piezoelectric coefficient measured was 5 pC/N for a PA 11/BaTiO3 700nm with φ = 0.4 poled under low field (3.3 kV/mm). It is higher than the piezoelectric coefficient of a stretched PA11 poled under high field (100 kV/mm).
Influence of molecular orientation on polarization phenomena in polyethylene terephthalate films
IEEE Transactions on Electrical Insulation, 1992
ABSTRACT
a-Relaxation/retardation mode in semicrystalline polymers with flexible chains
Polymer, 1994
Correlations between pyroelectricity, thermal transitions and dielectric relaxations in PVDF and related copolymers
Proceedings of 8th International Symposium on Electrets (ISE 8)
ABSTRACT
Thermal aging of pyroelectricity in PVDF and P(VDF-TrFE) copolymers
SPIE Proceedings, 1999
ABSTRACT
Physical ageing influence on chains dynamic of polycarbonate by thermo-stimulated currents (TSC)
Proceedings of the 2004 Ieee International Conference on Solid Dielectrics, Vols 1 and 2, 2004
The physical ageing in amorphous polymer, polycarbonate, is studied by complementary techniques: ... more The physical ageing in amorphous polymer, polycarbonate, is studied by complementary techniques: thermally stimulated currents ({TSC)} and differential scanning calorimetry ({DSC).} The enthalpy relaxation is described using the Tool, Narayanaswamy and Moynihan ({TNM)} phenomenological model where the relaxation time tau(H)({T,T-f)} depends both on temperature T and fictive temperature T-f characteristic of the glass structure. We have shown the structural dependence of enthalpy relaxation time give prominence to the compensation law observed in dielectric relaxation times.
Polarization phenomena associated with the microstructure of PEEK
Proceedings of 8th International Symposium on Electrets (ISE 8)
The microstructure of Poly (Ether Ether Ketone)/PEEK has been analysed by Thermo Stimulated Curre... more The microstructure of Poly (Ether Ether Ketone)/PEEK has been analysed by Thermo Stimulated Currents/TSC. The amorphous phase has been characterized by the kinetic of the molecular mobility involved in dielectric relaxation. Around the glass transition temperature, a complex TSC peak is observed: The lower temperature component, situated at 150°C, has been associated with cooperative movements in the “mobile amorphous phase” of PEEK. The higher temperature component, situated at 162°C, has been attributed to the existence of a “rigid amorphous phase” with local order induced by crystallites. The evolution of mechanical properties of PEEK upon crystallinity can be explained with the hypothesis of a three phase model: crystalline phase, mobile amorphous phase and rigid amorphous phase
Polarization phenomena as a characteristic of the 'structure' of the polymeric amorphous phase
6th International Symposium on Electrets,(ISE 6) Proceedings.
ABSTRACT
Influence of alkyl chain length on dielectric relaxations in poly(n-alkyl methacrylates)
Proceedings. 11th International Symposium on Electrets
Relations between chain structure and the dynamic of molecular movements are studied in the glass... more Relations between chain structure and the dynamic of molecular movements are studied in the glass transition temperature range for a series of amorphous model polymers: the poly(n-alkyl methacrylates). Two dielectric spectroscopies are used in order to enlarge the accessible frequency range: the dynamic dielectric spectroscopy and the thermo-stimulated currents technique. We show the existence of three dipolar relaxation modes: the /spl alpha/ mode assigned to the glass relaxation, the /spl beta/ mode, a secondary relaxation mode, below Tg and the /spl alpha/' mode, above Tg, dielectric manifestation of the liquid-liquid transition. We follow the shift of these relaxations with frequency, determine the behaviour laws of relaxation times and the fine structure of these complex modes. From the comparison of these results, we identify the effect of the alkyl group length on the relaxations and we, propose a phenomenological model to describe the molecular mobility through the glass transition.
DSC and TSC study of a VDF/TrFE copolymer
Thermochimica Acta, 1993
ABSTRACT
Sensors and Actuators B: Chemical, 2005
This paper reports on the fabrication of a new capacitive humidity sensor having good characteris... more This paper reports on the fabrication of a new capacitive humidity sensor having good characteristics and being robust enough to be considered as a component in industrial processes. This sensor is manufactured using a mixture of three cellulose acetate butyrates cross-linked by a melamine formaldehyde resin as sensing material. Details of the fabrication process and sensor characteristics such as linearity, sensitivity, hysteresis, response time, maximum operating temperature or physical and chemical stresses influence are included.
α-Relaxation/retardation mode in semicrystalline polymers with flexible chains
Polymer, 1994
ABSTRACT
Polymer, 2002
A comparative study by thermo-stimulated currents (TSC) of three poly(n-alkyl methacrylates) is p... more A comparative study by thermo-stimulated currents (TSC) of three poly(n-alkyl methacrylates) is performed. TSC complex spectra exhibit two dipolar relaxations considered in the following: the glass relaxation and a secondary relaxation related to motion of ester side groups. For each sample, the fractional polarisations protocol is applied to describe the fine structure of these complex spectra. It allows us to define the evolution of activation parameters with temperature. The influence of side chain architecture is then considered. It emphasises that the b mode is independent of the ester group length. On the contrary, the a mode is highly sensitive to structural change. These results are finally explained in terms of molecular mobility.
Macromolecules, 2002
The study of poly(n-hexyl methacrylate) has been performed by both thermo-stimulated currents (TS... more The study of poly(n-hexyl methacrylate) has been performed by both thermo-stimulated currents (TSC) and dynamic dielectric spectroscopy (DDS) in order to better define the nature of molecular mobility in the glass transition temperature range. TSC results reveal the existence of three dipolar relaxation modes: R, ascribed to the glass relaxation; , assigned to a secondary relaxation mode; and R′, associated with the dielectric manifestation of the liquid-liquid transition. DDS allowed us to follow the merging of the R and modes as frequency increases from 10-2 to 10 6 Hz. Then the fractional polarizations protocol permitted us to define at low frequency (10-3-10-2 Hz) the fine structure of these complex relaxations: relaxation times isolated for the and R modes are widely distributed and obey an Arrhenius law while those isolated for the R′ mode are narrowly distributed and are better defined by a Vogel-Tamman-Fulcher law. Finally, the evolution of the activation enthalpy helps us to precise the nature of involved molecular movements.
Study by Thermostimulated Currents of Dielectric Relaxations through the Glass Transition in an Amorphous Polymer: Poly( n -butyl methacrylate)
Macromolecules, 2001
ABSTRACT
Journal of Thermal Analysis, 1992
The ThermoStimulated Current (TSCu) and ThermoStimulated Creep (TSCr) spectroscopies have been ap... more The ThermoStimulated Current (TSCu) and ThermoStimulated Creep (TSCr) spectroscopies have been applied to the investigation of amorphous phases of polymeric materials. We have analysed the molecular mobility liberated at the glass transition temperature and the compensation diagram has been used for characterizing the corresponding cooperative movements. In linear polymers, the influence of chemical and physical structures has been investigated. In polymeric networks, the evolution of the structure towards chemical composition has been shown.
Cooperative relaxations/transitions in ferroelectric polymers
Journal of Thermal Analysis, 1993
ABSTRACT Dielectric relaxation and thermal transitions in β-PVDF have been investigated by Thermo... more ABSTRACT Dielectric relaxation and thermal transitions in β-PVDF have been investigated by Thermo-Stimulated Current spectroscopy and Differential Scanning Calorimetry respectively. A comparative study of spectra and thermograms has been performed. The relaxation mode associated with the glass transition of the true amorphous phase is characterized by relaxation times obeying a compensation law due to cooperative molecular movements. A conformationally disordered structure is proposed for β-PVDF to explain thermal events occurring around 60°C. Ageing of ferroelectric properties of β-PVDF has been associated with cooperative molecular movements liberated largely below the melting point. Mittels TSC und DSC wurden die Dipolrelaxation und thermische Umwandlungen von β-PVDF untersucht und dann eine vergleichende Analyse der Spektren und Thermogramme durchgeführt. Die Realaxationsart bei der Glasumwandlung der echten amorphen Phase wird wegen zusammenhängender Molekülbewegungen durch Relaxationszeiten gekennzeichnet, die dem Kompensationsgesetz folgen. Zur Deutung der thermischen Vorgänge bei 60°C wird für β-PVDF eine konformativ ungeordnete Struktur vorgeschlagen. Die Alterung der ferroelektrischen Eigenschaften von β-PVDF wird mit den zusammenhängenden Molekülbewegungen in Zusammenhang gebracht, die unterhalb des Schmelzpunktes ausgeführt werden.
Journal of Polymer Science Part B: Polymer Physics, 1995
The thermal and dielectric behavior of P-PVDF and a series of random P(VDF-TrFE) copolymers with ... more The thermal and dielectric behavior of P-PVDF and a series of random P(VDF-TrFE) copolymers with various chemical composition has been investigated in the temperature range of their Curie transition. Dielectric relaxations and phase transitions were characterized by means of differential scanning calorimetry and thermostimulated current spectroscopy. The thermal hysteresis associated with the first order character of the Curie transition decreases as the TrFE content increases, and vanishes for P (VDF-TrFE) 50/ 50. For the latter, the distribution in lamellar thickness and the dependence of the conformational order in the ferroelectric phase upon thermal history yield an intricate thermal behavior. For the overall investigated polymers, the TSC mode associated with the ferro/ para-electric transition is described by a distribution in relaxation times obeying a compensation law. This behavior has been interpreted based on cooperative movements in the ferroelectric phase in the vicinity of the transition temperature. These molecular movements are precursors of the transition. It is valid for P-PVDF, as well as for P(VDF-TrFE) copolymers which for the compensation temperature corresponds to the transition temperature. So, the Curie temperature of PVDF has been found at 17OoC, i.e. the melting point.
Comparative study of Poly(n-butyl methacrylate) by thermo-stimulated currents and dynamic dielectric spectroscopy
Journal of Physics D: Applied Physics, 2001
ABSTRACT
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Papers by Colette Lacabanne