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Publications (3)1.52 Total impact

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    ABSTRACT: This work reports on the relationship between structure and dielectric properties of biaxially oriented polypropylene. The morphology of semi-crystalline bioriented isotactic polypropylene (BOiPP) films is investigated using Wide Angle X-ray Diffraction (WAXD) and Polarized Optical Microscopy (POM). A β-orthorhombic structure, with a crystallinity ratio of about 46%, and a “Crater” morphology of the β-form is identified. Dielectric properties are measured by Broadband Dielectric Spectroscopy (BDS) over a wide temperature range (-150°C to 125°C). Since the dissipation factor of the PP is very low, special care was taken to obtain valid data. Two main relaxation processes are observed: a α-relaxation peak associated to the glass transition temperature (Tg) at low frequency and temperature about -7°C, and a broad β*-relaxation at high frequency at about -60°C, attributed to CH orientation. The variation of the dissipation factor versus sample thickness (from 3.8 μm to 11.8 μm) is correlated and explained by the increase of crystallinity ratio at larger thicknesses.
    Solid Dielectrics (ICSD), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: The dielectric properties of two grades of Bi-oriented isotactic polypropylene (BOiPP) are studied, using a variety of techniques: breakdown field measurements, dielectric spectroscopy, thermally stimulated depolarization currents, dc conduction currents. Standard (STPP) and high-crystallinity (HCPP) polypropylene films are investigated. Measurements are carried out over a wide temperature range, up to (-150°C/ +125°C). Breakdown field in both materials show a very small difference. On the other hand, dielectric losses and dc conduction currents are significantly lower in HCPP. Both materials show a decrease of dielectric losses versus temperature in the range (20-90°C), favorable for the application to ac power capacitors. The analysis of dc currents allows to evidence two main conduction mechanisms: (i) below 80°C in both materials, a hopping mechanism due to motion of electrons occurring in the amorphous phase; (ii) above 80°C, an ionic conduction in HCPP and a hopping conduction in STPP.
    Solid Dielectrics (ICSD), 2013 IEEE International Conference on; 01/2013
  • C. Guillermin, O. Dujeu, J.-M. Lupin
    IEEE Transactions on Power Delivery 03/2012; · 1.52 Impact Factor