Breakdown-induced light emission and poling dynamics of porous fluoropolymers

To date the charging mechanism of porous electret materials is not completely understood. The present study is focused on the investigation of light emission during corona poling of individual films of expanded polytetrafluoroethylene (ePTFE) with nominal porosity of 91% and of the same film sandwiched between two solid poly-fluroethylene propylene copolymer (FEP) films. One observes that as soon as the applied electric field exceeds a certain threshold value (Vth), the individual film and sandwiched structure start to emit light. For the sandwich structure the light intensity decays with time to zero, whereas for an individual ePTFE film a continuous light emission at V>Vth is observed. The emitted light is a result of electrical breakdown events in air developing in the pores of the media. For the sandwich sample the positive and negative charges generated during breakdown are trapped at opposite ePTFE/solid film interfaces, thus resulting in a macroscopic dipole formation (polarization). In the case of...

[1]  H. Seggern,et al.  Breakdown-induced polarization buildup in porous fluoropolymer sandwiches: a thermally stable piezoelectret , 2006 .

[2]  H. Seggern,et al.  Air-breakdown charging mechanism of fibrous polytetrafluoroethylene films , 2005 .

[3]  Reimund Gerhard-Multhaupt,et al.  Less can be more. Holes in polymers lead to a new paradigm of piezoelectric materials for electret transducers , 2002 .

[4]  Siegfried Bauer,et al.  Dielectric barrier microdischarges: Mechanism for the charging of cellular piezoelectric polymers , 2002 .

[5]  Werner Wirges,et al.  Thermally stable dynamic piezoelectricity in sandwich films of porous and nonporous amorphous fluoropolymer , 2001 .

[6]  M. Paajanen,et al.  Determination of the actuator sensitivity of electromechanical polypropylene films by atomic force microscopy , 2000 .

[7]  S. Bauer,et al.  Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets , 2000 .

[8]  R. Gerhard-Multhaupt,et al.  Piezoelectricity of porous polytetrafluoroethylene single- and multiple-film electrets containing high charge densities of both polarities , 2000 .

[9]  J. Hillenbrand,et al.  Electromechanical response of cellular electret films , 1999, 10th International Symposium on Electrets (ISE 10). Proceedings (Cat. No.99 CH36256).

[10]  Reimund Gerhard-Multhaupt,et al.  High surface-charge stability of porous polytetrafluoroethylene electret films at room and elevated temperatures , 1999 .

[11]  Mauro M. Costa,et al.  Corona charging of polymers: recent advances on constant current charging , 1999 .

[12]  J. Giacometti,et al.  Study of poling behavior of biaxially stretched poly(vinylidene fluoride) films using the constant‐current corona triode , 1995 .

[13]  Iu. P. Raizer.  Gas Discharge Physics , 1991 .

[14]  Yuri P. Raizer,et al.  Breakdown of Gases in Fields of Various Frequency Ranges , 1991 .

[15]  H. Seggern.  Isothermal and thermally stimulated current studies of positively corona charged polyfluoroethylenepropylene (Teflon FEP) , 1981 .