Title :
Correlations between pyroelectricity, thermal transitions and dielectric relaxations in PVDF and related copolymers
Author :
Teyssedre, Gilbert ; Bernes, Alain ; Lacabanne, Colette
Author_Institution :
Lab. de Phys. des Solides, Univ. Paul Sabatier, Toulouse, France
Abstract :
The temperature dependence of the pyroelectric coefficient of PVDF and P(VDF-TrFE)75/25 has been correlated with thermal transitions and dielectric relaxations as revealed by DSC and TSC. For both polymers, three changes in slope have been found: the lower temperature one corresponds to the glass transition of the free amorphous phase of the polymers. An upper component of the glass transition, Tgu(10/20°C) has been ascribed to the glass transition of the amorphous phase constrained by crystallites. The α process occurs at 40/50°C. It has been associated with conformational reorganizations related to the crystalline phase. It plays a key role in ageing of electroactive properties. Above Tα, cooperative movements are liberated. They are precursors of the Curie transition
Keywords :
crystallites; dielectric relaxation; electrets; ferroelectric Curie temperature; ferroelectric materials; glass transition; polymer blends; polymers; pyroelectricity; thermal analysis; thermally stimulated currents; -120 to 120 C; Curie transition; DSC; P(VDF-TrFE) copolymers; PVDF; TSC; conformational reorganization; cooperative movements; crystalline phase; crystallite constrained amorphous phase; dielectric relaxations; electrets; ferroelectrics; free amorphous phase; glass transition; pyroelectricity; temperature dependence; thermal transitions; Amorphous materials; Crystallization; Dielectrics; Ferroelectric materials; Glass; Heating; Polarization; Polymers; Pyroelectricity; Temperature dependence;
Conference_Titel :
Electrets, 1994. (ISE 8), 8th International Symposium on
Conference_Location :
Paris
Print_ISBN :
0-7803-1940-0
DOI :
10.1109/ISE.1994.514846
