High surface-charge stability of porous polytetrafluoroethylene electret films at room and elevated temperatures

Xia, Zhang; Gerhard, Reimund; Künstler, W.; Wedel, Armin; Danz, R.

doi:10.1088/0022-3727/32/17/102

Cited by 113 publications

(60 citation statements)

References 9 publications

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“…Piezoelectric properties of porous PTFE foams have already been reported some time ago (29,30) . The high surface charge stability of these materials in particularly elevated temperatures range has been confirmed (31,32,33) and also in independent experiments (34,35) . To some extent, the stability of the surface potential and of the resulting piezoelectric response were found to improve with increasing porosity to some extent (23) .…”

Section: Materials Characteristicsmentioning

confidence: 63%

Ceramic Based Intelligent Piezoelectric Energy Harvesting Device

Patel¹

2011

Advances in Ceramics - Electric and Magnetic Ceramics, Bioceramics, Ceramics and Environment

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Section: Materials Characteristicsmentioning

confidence: 63%

Ceramic Based Intelligent Piezoelectric Energy Harvesting Device

Patel¹

2011

Advances in Ceramics - Electric and Magnetic Ceramics, Bioceramics, Ceramics and Environment

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“…Aging has also been known to improve the charge stability of electret materials. Several thermal treatments of the charging are referenced (see Refs [1,7]). In this paper, we investigated the charge storage properties with temperature resistance.…”

Section: Electret Properties Of Composite Filmsmentioning

confidence: 99%

“…The standard porous PTFE and the composite PTFE/COC films were both heated to 100 0 C and corona discharge performed (e.g. heating during charging process) at -800 V and -400 V of the grid voltage in order to limit the surface potential [1,7]. Experimental results (Figure 4) indicate that the standard porous PTFE (24 μm) and the composite PTFE/COC (25 μm) films exist at -328 V and -343 V of the initial surface potential.…”

Section: Electret Properties Of Composite Filmsmentioning

confidence: 99%

“…Current commercially available electret polymers which include polypropylene (PP), polyethyleneterephthalate (PET), cyclic olefin copolymers (COC), polytetrafluoroethylene (PTFE) and fluoroethylenepropylene (FEP), exhibit good charge storage capacity [1][2][3]. In particular, a thick porous PTFE exhibits excellent dielectric properties including high charge storage stability at high temperatures [4][5][6][7]. Widely used PTFE electret related applications include such items as electret condenser microphones (ECM), soft ferro-electret transducers and transdermal drug delivery (TDD) systems [5,[8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

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Charge storage and mechanical properties of porous PTFE and composite PTFE/COC electrets

Ko¹,

Tseng²,

Wu³

et al. 2010

E-Polymers

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Recent futuristic applications of flexible electret loudspeakers have garnered much interest for these novel loudspeakers. To increase the loudspeaker properties, a processing method was developed to improve the electret and mechanical properties of porous PTFE film. Taking a thin porous PTFE film as the base material, a cyclic olefin copolymer (COC) was coated to a base material to form a PTFE/COC composite film. Results show that the composite material improves the advantageous characteristics when used as an electret diaphragm for loudspeakers. By measuring the surface potential decay and the elastic modulus, properties of a standard porous PTFE film were compared to an improved composite PTFE/COC film. Experimental results showed that the composite PTFE/COC possess the following advantages: (1) 80% higher surface potential after 10 days at room temperature, (2) a better thermal resistance of charge storage, and (3) a 643% higher elastic modulus. Therefore, our novel composite material can be used to create a much improved electret diaphragm for flexible electret loudspeakers.

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“…Microporous PTFE [20,21], as well as the network-forming PFCB [22] were shown to be outstanding charge electrets when charged as single layers, comparable or even superior to standard PTFE. A hybrid stack consisting of the two fluoropolymers was also found to exhibit excellent charge storage properties [21].…”

mentioning

confidence: 99%

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

Neugschwandtner¹,

Schwödiauer²,

Bauer‐Gogonea³

et al. 2000

Appl Phys A

102

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Large piezoelectric d 33 coefficients around 600 pC/N are found in corona-charged non-uniform electrets consisting of elastically "soft" (microporous polytetrafluoroethylene PTFE) and "stiff" (perfluorinated cyclobutene PFCB) polymer layers. The piezoelectric activity of the twolayer fluoropolymer stack exceeds the d 33 coefficient of the ferroelectric ceramic lead zirconate titanate (PZT) by more than a factor of two and that of the ferroelectric polymer polyvinylidene fluoride (PVDF) by a factor of 20. Soft piezoelectric materials may become interesting for a large number of sensor and transducer applications, in areas such as security systems, medical diagnostics, and nondestructive testing. 77.84.Jd; 85.50.+k Piezoelectricity is the basis for a large number of sensor and transducer applications. Mass products emerge in security systems, medical diagnostics and nondestructive testing [1]. Basic science benefits from resonant ultrasound spectroscopy for the determination of acoustical properties of materials with sample masses of only a few µg [2]. Sensitive and low-cost piezoelectric materials are in high demand for these applications. In this rapid communication, very large piezoelectric coefficients are reported in charged heterogeneous electret films, surpassing all materials known so far. A heterogeneous two-layer electret stack, based on exceptionally stable fluoropolymer charge electrets is proposed and experimentally demonstrated. Preliminary results indicate not only very large, but also long-term stable piezoelectric effects, most promising for applications in sensor and transducer devices. PACS:Piezoelectric material constants relate second-order symmetric tensors (stress T or strain S) to vectors (displacement D or electric field E). Since electric field and stress are independent variables easily to control experimentally, the most often used piezoelectric tensor is the third-rank d-tensor relating displacement D and stress T (direct piezoelectric effect) or strain S and electric field E (inverse piezoelectricIn piezoelectric sensors and thickness mode resonators, the d 33 coefficient is employed, 3 denotes the polar axis and the contracted notation is used. A necessary condition for the occurrence of piezoelectricity is the absence of a center of symmetry, piezoelectric materials are therefore intrinsically anisotropic. Large piezoelectric coefficients are usually found in ferroelectric crystals and polymers. The most widely employed piezoelectric material, lead zirconate titanate (PZT), with a composition near the morphotropic phase boundary between the rhombohedral and tetragonal phase shows a d 33 coefficient of 220 pC/N [4]. Since the use of lead-containing materials is environmentally hazardous, the development of new piezoelectric materials is a matter of urgency. For a large number of applications, e.g. in medical ultrasound, low-density piezoelectric materials (such as polymers) are interesting, with an acoustic impedance matched to that of the human body. Unfortunately, the d 33 coeff...

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High surface-charge stability of porous polytetrafluoroethylene electret films at room and elevated temperatures

Cited by 113 publications

References 9 publications

Ceramic Based Intelligent Piezoelectric Energy Harvesting Device

Ceramic Based Intelligent Piezoelectric Energy Harvesting Device

Charge storage and mechanical properties of porous PTFE and composite PTFE/COC electrets

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

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