Influence of fillers on mechanical properties of ATH filled EPDM during ageing by gamma irradiation

International audienceThe presence of a significant content of fillers accelerates the degradation of ATH filled EPDM subjected to gamma irradiation at room temperature. Above the melting temperature of the EPDM, this induces a decrease in the apparent mechanical reinforcement of the fillers. This also promotes de-cohesion mechanisms which leads to an increase in the strain at break with irradiation dose. It is not clear whether the use of a filler treatment attenuates this accelerating effect or not; however, part of this treatment remains efficient at a high dose and seems also to delay but not suppress the occurrence of de-cohesion mechanisms at large strain. Moreover, at room temperature, i.e. below the melting temperature, all the consequences of ageing by gamma irradiation are strongly attenuated by the presence of a semicrystalline microstructure, the morphology of which is not too strongly modified by irradiation. (C) 2010 Elsevier Ltd. All rights reserved

Conformation and crystallinity in polymers : a study using novel Roman techniques

Crystallinity and conformation of biopolymers, polyamides and even numbered normal paraffins were studied using novel Raman techniques. The newly developed Fourier transform Raman method was used for characterization of biopolymers and polyamides. Low frequency modes of vibration by conventional Raman spectroscopy were investigated in terms of structure for the paraffins. The temperature dependence of the low frequency and internal mode regions were studied for even n-paraffins from C22H46 to C36H74 and for the binary mixture C28H58 &#43; C30H62. Particular emphasis was placed on temperatures just below the melting point. The lattice packing in the crystals was found to depend on the history of the sample crystallization. As the temperature was raised up to the solid-solid phase transition, a change from two chains per unit cell to one chain was observed. The degree of order was found to decrease as the temperature increased but no evidence of the presence of defects was detected. The study of the binary mixture suggests that the chains in the mixture do not vibrate as isolated rods but rather like the longest hydrocarbon component. The FT Raman spectra of three solid homopolypeptides were acquired for the first time. These spectra show mainly sharp bands arising from the characteristic side group vibrations. The corresponding infrared spectra exhibit predominantly bands arising from secondary amide vibrations broadened by OH species absorptions. Thus identification was more readily achieved with the Raman technique. Studies in the liquid state led to the conclusion that considerable improvements in sensitivity are needed before the method becomes useful to biochemists. Aliphatic polyamides of the type nylon X and nylon X,Y were characterized by FT Raman. The spectra obtained tended towards that of polyethylene as the number of methylene group per repeat unit increases. The FT Raman study of samples of nylon 6 with different crystallinity led to the conclusion that this technique has the potential to give a quantitative measure of percentage crystallinity. Evidence is presented that FT Raman spectroscopy may be capable of distinguishing between various nylon copolymers. In contrast, it was confirmed that the infrared study of aliphatic polyamides does not provide an easy means to their identification since the strongest bands arise from the secondary amide vibrations and sample preparation in the form of film was required.</p

Théorie de la spectroscopie vibrationnelle

International audienc

In Situ Study of Plastic Micro-Mechanisms of Deformation Involved during Stretching Forvarious composites based on Isotactic Polypropylene: Characterization of Macromolecular Chains Orientation and Volume damage

Simulation and prediction of the thermo-mechanical behavior of composites based on thermoplastic polymers do not cease arousing the interest of a wide range of manufacturers in the automotive industry, for instance. Therefore, the determination of mechanical behavior laws must be the most efficient as possible. The key parameter to take into account is the microstructure evolution of the polymers during the mechanical solicitation [1-6]. This paper focuses on the characterization of the irreversible microstructural mechanisms involved during plastic deformation stage of uniaxial stretching tests. The matrix material of the study is the isotactic polypropylene (iPP) declined in various forms: a neat iPP, an impact iPP (PP/EPR) and two PP/EPR composites filled with mineral particles (µ-talc and CaCO3). The various compositions of these materials allow highlighting the competition between the macromolecular chains orientation mechanism and the volume damage process. Raman spectroscopy analyses are performed in real time during the mechanical solicitation using the VidéoTraction™ system [2, 5-7]. This innovative coupling system enables to follow the evolutions of the different studied composites microstructures. Results brought by Raman spectroscopy are correlated with others common analyses techniques such as in situ Wide Angle X-ray Scattering (performed with high energy synchrotron radiation on the P07 beamline at PETRAIII, Hamburg, Germany), in situ Incoherent Steady Light Transport and in situ Scanning Electron Microscopy observations

In situ study of plastic micro-mechanisms of deformation involved during stretching forvarious composites based on isotactic polypropylene: characterization ofmacromolecular chains orientation and volume damage.

Simulation and prediction of the thermo-mechanical behavior of composites based on thermoplastic polymers do not cease arousing the interest of a wide range of manufacturers in the automotive industry, for instance. Therefore, the determination of mechanical behavior laws must be the most efficient as possible. The key parameter to take into account is the microstructure evolution of the polymers during the mechanical solicitation [1-6]. This paper focuses on the characterization of the irreversible microstructural mechanisms involved during plastic deformation stage of uniaxial stretching tests. The matrix material of the study is the isotactic polypropylene (iPP) declined in various forms: a neat iPP, an impact iPP(PP/EPR) and two PP/EPR composites filled with mineral particles (µ-talc and CaCO3). The various compositions of these materials allow highlighting the competition between the macromolecular chains orientation mechanism and the volume damage process. Raman spectroscopy analyses are performed in real time during the mechanical solicitation using the VidéoTraction™ system [2, 5-7]. This innovative coupling system enables to follow the evolutions of the different studied composites microstructures. Results brought by Raman spectroscopy are correlated with others common analyses techniques such as in situ Wide Angle X-ray Scattering (performed with high energy synchrotron radiation on the P07 beamline at PETRAIII, Hamburg, Germany), in situ Incoherent Steady Light Transport and in situ Scanning Electron Microscopy observations

Analyse diélectrique en tension et température de câbles à isolation PVC après exploitation

National audienc

Real‐time Raman spectroscopy measurements to monitor the effect of polypropylene crosslinking on its true mechanical behaviour

International audienc

Dielectric relaxation behaviour in semi-crystalline polyvinylidene fluoride (PVDF)/TiO2 nanocomposites

International audiencePolymer nanocomposites based on polyvinylidene fluoride (PVDF) matrix filled with TiO2 nanoparticles (1%, 2%, 3% and 5% by v/v%) were studied by broadband dielectric spectroscopy (BDS) in order to investigate the filler effect on the molecular mobility of the polymer chains. The formalism of electric modulus was used to analyze the dielectric response, thus three relaxation processes were observed. In fact, the first one, which is around ―40 °C at 10 Hz, is attributed to the glass transition at low temperature. As for the second phenomenon, around 30 °C at 10 Hz, it is related to the dipolar relaxations in the crystalline phase. Regarding the third one, around 100 °C at 10 Hz, it can be due to the interfacial polarization (IP). The crystallinity ratio decreases and the electric modulus of the interfacial polarization increases with the increase of the TiO2 content