Capacitance Dilatometry for the in-situ Controlled Expansion Process of Cellular Polymer-Filler Composites (Ferroelectrets)

Leonhartsberger, J.G.; Salhofer, H.; Schwödiauer, Reinhard; Bauer‐Gogonea, S.; Bauer, Siegfried; Forstner, R; Eder, G.; Paajanen, Mika; Minkkinen, Hannu; Raukola, J.

doi:10.1080/00150190600737735

Cited by 9 publications

(5 citation statements)

References 12 publications

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“…The capacitance of the sample is expected to increase during the pressure increase (b) and finally to decrease below the initial value during the sudden release of the pressure (c) (after ref. [18]). Figure 5.…”

Section: à3mentioning

confidence: 93%

“…Recent investigations have revealed a frequency dependence of the piezoelectric response at very low frequencies, which was ascribed to the viscoelastic properties of piezoelectric polymers. [16][17][18] So far, no attempt to measure the shear piezoelectric coefficients of cellular polymers has been reported. The determination of shear piezoelectric coefficients in polymers is a difficult task, and even for traditional piezoelectric polymers, such as PVDF, only few reports are available.…”

Section: Piezo-and Pyroelectricity Of Internally Charged Cellular Polmentioning

confidence: 99%

“…In a second process step after coextrusion and biaxial stretching, the size of the voids can be varied by an inflation process, based on a high-pressure treatment and a subsequent heat-setting process. [12][13][14][15][16][17][18] For the controlled inflation of the voids in the cellular polymer, the external gas pressure is usually raised and kept at a high value for a certain time (Figure 4). …”

Section: à3mentioning

confidence: 99%

“…The polymer is inflated by a subsequent sudden release of the external gas pressure (Figure 4). [13][14][15][16][17][18] The inflated structure needs to be stabilized by a thermal treatment above ambient temperature. [15] The thermal treatment increases the crystallinity of the polymer matrix, as revealed by differential scanning calorimetry, thereby stiffening and stabilizing the foam structure.…”

Section: à3mentioning

confidence: 99%

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Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

2005

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Cellular polymers can be internally charged by "microstorms" (silent or partial discharges) within the voids of the polymer foam. The resulting material, which carries positive and negative charges on the internal void surfaces, is called a ferroelectret. Ferroelectrets behave like typical ferroelectrics, hence they provide a novel class of ferroic materials. The soft foams are strongly piezoelectric and can be used, in a wide range of applications, as transducers for interconverting mechanical and electrical signals. Herein, an overview is provided on the preparation of cellular polymers by physical foaming (extrusion, biaxial stretching, and controlled inflation by pressure treatments), on their charging by "microstorms", on their piezo- and pyroelectricity, and on analogies to ferroelectrics. Finally, a survey of selected applications is presented.

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Section: à3mentioning

confidence: 93%

Section: Piezo-and Pyroelectricity Of Internally Charged Cellular Polmentioning

confidence: 99%

Section: à3mentioning

confidence: 99%

Section: à3mentioning

confidence: 99%

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Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

2005

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“…They are produced by stretching filler-loaded PP under suitable conditions. 25,26 Figure 1 shows the normalized capacitance decay in dry air at different pressures. In order to optimize their electromechanical properties, the samples were inflated by gas-diffusion expansion in nitrogen and subsequent heat treatment.…”

mentioning

confidence: 99%

Influence of gas pressure in the voids during charging on the piezoelectricity of ferroelectrets

Qiu

Mellinger

Gerhard

2008

Applied Physics Letters

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Nonlinear capacitance dilatometry for investigating elastic and electromechanical properties of ferroelectrets

Bauer‐Gogonea

Camacho-Gonzalez

Schwödiauer

et al. 2007

Applied Physics Letters

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Nonlinearities in ferroelectret polymer foam capacitors arise from voltage-dependent thickness changes. Such thickness changes are caused by the converse piezoelectric and electrostrictive effects in these soft materials. The authors show that the higher harmonics of the current response during application of a sinusoidal voltage to ferroelectret capacitors provide information on the elastic and electromechanical properties of the foam. The authors demonstrate the potential of this versatile measurement technique by investigating the temperature dependence of the piezoelectric response and by monitoring the changes in the elastic and electromechanical properties during inflation of cellular polypropylene.

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Capacitance Dilatometry for the in-situ Controlled Expansion Process of Cellular Polymer-Filler Composites (Ferroelectrets)

Cited by 9 publications

References 12 publications

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles

Influence of gas pressure in the voids during charging on the piezoelectricity of ferroelectrets

Nonlinear capacitance dilatometry for investigating elastic and electromechanical properties of ferroelectrets

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