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Structure effect of thin film polypropylene view by dielectric spectroscopy and X‐ray diffraction: Application to dry type power capacitors
Author(s) -
Kahouli Abdelkader,
GallotLavallée Olivier,
Rain Pascal,
Lesaint Olivier,
Heux Laurent,
Guillermin Christophe,
Lupin JeanMarc
Publication year - 2015
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.42602
Subject(s) - crystallinity , materials science , dielectric , dissipation factor , composite material , relaxation (psychology) , tacticity , polypropylene , diffraction , dielectric spectroscopy , optics , polymer , chemistry , optoelectronics , physics , psychology , social psychology , polymerization , electrode , electrochemistry
This work reports on the relationship between structure and dielectric properties of biaxially oriented polypropylene. The morphology of semicrystalline bioriented isotactic polypropylene films is investigated using wide angle X‐ray diffraction and Polarized Optical Microscopy. A β‐orthorhombic structure, with a crystallinity ratio of about 46%, and “Crater” morphology of the β‐form is identified. Dielectric properties are measured by Broadband Dielectric Spectroscopy over a wide temperature range (−150 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 temperature about −7°C, and a broad β*‐relaxation at about −60°C, partly attributed to CH orientation. The variation of the dissipation factor versus sample thickness (from 3.8 to 11.8 µm) is correlated and partly explained by the increase of crystallinity ratio and lamella size at larger thicknesses. It comes out that the thinnest film seems perfectly meet the application requesting, namely lowest dissipation factor and highest permittivity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 42602.