Charge storage behavior of isotropic and biaxially‐oriented polypropylene films containing α‐ and β‐nucleating agents

Behrendt, Nico; Mohmeyer, Nils; Hillenbrand, J.; Klaiber, Martin; Zhang, Xiaoqing; Sessler, G. M.; Schmidt, Hans‐Werner; Altstädt, Volker

doi:10.1002/app.22502

Cited by 77 publications

(77 citation statements)

References 25 publications

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“…There is currently no special class of polymer additive that is intentionally designed for electret purposes; however, nucleating agents, antioxidants, light stabilizers, fluorochemicals, and inorganic ceramic ferroelectrics were investigated. Nucleating agents either provide smaller spherulites whose boundaries are traps for space charges, or generate microvoids that prohibit charge migration (Behrendt et al 2006;Mohmeyer et al 2006Mohmeyer et al , 2007. Antioxidants and light stabilizers can act as nucleators and also provide deep charge traps (Cartwright et al 1996;Rousseau et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Electrostatic Capture Efficiency Enhancement of Polypropylene Electret Filters with Barium Titanate

Kılıç

Shim

Pourdeyhimi

2015

Aerosol Science and Technology

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This study reports on the effects of BaTiO 3 -a high dielectric constant additive-addition on charging and filtration properties of meltblown polypropylene (PP) electret filters. Since electrostatic capture efficiency of electret filters is mainly dependent on electrical forces, surface potential and aerosol filtration properties were analyzed and compared. Due to quasipermanent nature of electret property, stability of charging and filtration performance was also investigated via following an isothermal charge decay procedure. Addition of BaTiO 3 did not alter fiber morphology significantly. Particularly, the stability of electrostatic filtration performance was found to be promising with the addition of BaTiO 3 . Possible microstructural changes after addition of BaTiO 3 were investigated via wide angle X-ray diffraction. Changes in crystal structure of PP upon addition of BaTiO 3 did not deteriorate electrostatic properties.

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Section: Introductionmentioning

confidence: 99%

Electrostatic Capture Efficiency Enhancement of Polypropylene Electret Filters with Barium Titanate

Kılıç

Shim

Pourdeyhimi

2015

Aerosol Science and Technology

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“…[26][27][28] Thus, the formation and the enlargement of voids, respectively, are confirmable by decrease of the density. The density measurements are shown in Table 1.…”

Section: Morphology Of the Expanded Filmsmentioning

confidence: 81%

“…A very regular spherulite particle size distribution and a low spherulite size are archieved through this nucleation effect, counteracting the brittleness. [26,28] Another reason is the structure of the generated cavities (Fig. 3).…”

Section: Analysis Of the Temperature Dependence Of The D 33 -Coefficientmentioning

confidence: 99%

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Piezoelectricity of Cellular Polypropylene Films Expanded by a Dichlormethane Evaporation Process

et al. 2008

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Piezoelectric effects in polar polymers are known for over 30 years, especially in b-PVDF. [1] In 1995, weak piezoelectric effects were also found in multilayer polymer films. Kacprzyk succeeded in verifying those piezoelectric effects in duallayer dielectrics, on basis of polypropylene/polyurethaneelectret sandwich systems after a corona charging. The relatively low piezoelectric d 33 -coefficient, of about 4 pC/N was obtained due to the different elasticity of the polymer layers. [2] In 1996, electromagnetic transducer coefficients of 30 pm/V in corona-charged cellular i-PP films were detected and such films were utilised for first applications. [3] A few years later, those effects were characterised by models of the cellular materials. [4][5][6][7] Through the corona charging [8] of thin cellular polypropylene films, with very high electric voltages, breakdowns in the individual pores are caused by micro plasma discharges. [7,9] After the electric breakdown the space charges are deposited at the interfaces of the cells. By applying a mechanical tension, the charged pores act as macroscopic dipoles; therefore the films show, with appropriately fixed electrodes on the surfaces of the film, a clearly measurable piezoelectric activity, since the system reacts to this change of the polarisation with a compensation current in the electrodes. [4,[10][11][12][13] The accuracy of a piezoelectric model was verified through the good correlation of the calculated and measured d 33 -coefficients. [14,15] Such cellular polypropylene films show an anisotropic, lentoid cavity structure. [16,17] As the charged cellular films were applied in electro mechanical transducers, such as acoustic sensors, [16,17] their production processes and the charging methods were further investigated. Based on this, other influence factors on the piezoelectric activity, such as the effect of heat treatment [5,10] and UV radiation with short wave length, [18,19] were studied.Recently some articles concerning the optimising of the piezoelectric activity of cellular films by using gas-expansion processes, were published. [20][21][22] The role of geometric shape of the cells, [23,24] and the influence of the gas in the cells, during the charging, [25] were closely studied. The development of expansion processes under high pressure for achieving large piezoelectric coefficients is one of the main focuses in today's research. [20][21][22] In the present paper, a new method for expanding stretched cellular i-PP films [26,27] is introduced. This process consists of three steps. Firstly, the cellular i-PP films with small cavities are saturated with dichlormethane (DCM). Then the DCM is abruptly evaporated at an elevated temperature of 120°C to expand the cavities inside the films. Finally, the expanded film samples are quenched in liquid nitrogen, to fix the cell structure. Experimental MaterialsAn isotactic polypropylene reactor powder, supplied by Borealis Linz, Austria, was used for the investigations. The weight average molecular weight was 425.000 ...

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“…The films were charged for 30 s in a standard point-to-plate corona triode employing a grid voltage of þ400 V (grid size: 0.2 mm) and a corona voltage of þ12.5 kV. [15][16][17][18]24,29,[32][33][34] The grid ensures uniform film surface potentials between 400 V and 420 V. [35] The charge storage characteristics of the obtained electret films were evaluated by the ITPD method. Here the surface potential of the electrets films is determined as a function of the exposed time at elevated isothermal temperatures, which was the standard temperature of T ITPD ¼ 90 8C unless otherwise noted.…”

Section: Physical Agingmentioning

confidence: 99%

Tailored Additives to Improve the Electret Performance of Polycarbonates

Erhard

Lovera

Jenninger

et al. 2010

Macro Chemistry & Physics

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An electret is a dielectric material exhibiting a quasi‐permanent electric charge. The aim of this work is to give access to PC electret materials with a distinctly improved electret performance. In this context, the charge storage capabilities of corona charged films of several PC grades were investigated by isothermal potential decay measurements at 90 °C. The most promising PC grade was further improved by a new class of bisimide additives. The best additive at the most efficient concentration in combination with a physical aging step yielded excellent PC electrets maintaining almost their complete applied charge even at 90 °C.

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Charge storage behavior of isotropic and biaxially‐oriented polypropylene films containing α‐ and β‐nucleating agents

Cited by 77 publications

References 25 publications

Electrostatic Capture Efficiency Enhancement of Polypropylene Electret Filters with Barium Titanate

Electrostatic Capture Efficiency Enhancement of Polypropylene Electret Filters with Barium Titanate

Piezoelectricity of Cellular Polypropylene Films Expanded by a Dichlormethane Evaporation Process

Tailored Additives to Improve the Electret Performance of Polycarbonates

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