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DF: Dielektrische Festkörper
DF 3: FV-internes Symposium „Polare Polymere und Ferroelektrete“
DF 3.8: Talk
Saturday, March 5, 2005, 11:40–12:00, TU C130
Influence of the amorphous phase on piezoelectricity in polyamide 11 — •Peter Fruebing, Alexander Kremmer, and Reimund Gerhard-Multhaupt — Department of Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam
Odd-numbered polyamides can form ferroelectric domains, in which the polymer chains are aligned in parallel and all amide-group dipoles are oriented perpendicular to the chains and parallel to each other. The domain structure is thermally stable up to the melting region (170 ∘C) because the amide groups are linked by hydrogen bonds. However, the piezoelectric d33 coefficient of 4 pC/N that can be achieved on extruded polyamide-11 films after uniaxial stretching at room temperature and electrical poling above the coercive field (75 MV/m) is relatively small. This is probably a consequence of the existence of a rigid amorphous phase where dipole orientation is sterically hindered. Furthermore, there are also relaxation contributions to the polarisation which may arise from a glass-forming amorphous phase.
Dielectric relaxation spectroscopy, dynamic mechanical analysis, differential scanning calorimetry and infrared spectroscopy are employed after various preparation steps (stretching, poling and annealing) in order to understand in particular the role of different amorphous phases for dipole orientation and dipole libration and thus possible restrictions for the piezoelectric response.