Corona charging of electrets: models and results

Ferreira, G. F. Leal; Figueiredo, M.T.

doi:10.1109/14.155789

Cited by 40 publications

(16 citation statements)

References 74 publications

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“…Electrostatic charges are commonly injected to polymeric fibers in order to improve the use of these materials in electrostatic filtration applications (Ferreira & Figueiredo, 1992; Kim et al ., 2006). Polymeric materials containing electrostatic charges are called electrets and have been widely used as air filters and respiratory masks.…”

Section: Introductionmentioning

confidence: 99%

Direct observation of the spatial distribution of charges on a polypropylene fiber via Electrostatic Force Microscopy

Ávila

Montenegro

Hinestroza

2012

Journal of Microscopy

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SummaryThe spatial distribution of electrical charges along the longitudinal axes of a polypropylene electret fiber was determined using Electrostatic Force Microscopy (EFM). EFM mapping on highly curved surfaces, such as those of polymeric fibers, is a challenging endeavour and most work reported in the scientific literature has been limited to single linescan analysis or flat specimens. Charged polymeric fibers, electrets, are extensively used in high performance filtration applications and methods to determine the amount and magnitude of the charges on these fibers remain elusive. Electrical charge maps of individual fibers were obtained by biasing the tip to -10 V and maintaining a constant tipsample distance of 100 nm. Spatially dependant EFM phase and magnitude gradients were determined and the developed technique may provide a unique understanding into the heterogeneous charge distribution on electrets fibers. Direct mapping of the charge distribution in electrets fibers can offer new insights in the development of antistatic additives, new means to facilitate electrostatic self-assembly of nano-moieties on the surface of fibrous materials and a quantitative metrics capable of determining discharge dynamics and predicting the shelf-life of filtration media.

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Section: Introductionmentioning

confidence: 99%

Direct observation of the spatial distribution of charges on a polypropylene fiber via Electrostatic Force Microscopy

Ávila

Montenegro

Hinestroza

2012

Journal of Microscopy

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“…Secondly, we plainly see a cross-over effect in the decay of the surface potential in our electret samples, whereby the samples charged to higher initial surface potentials decay faster and reached the lower overall final potentials. This is a well known effect in polyethylenes charged by corona [48]. Mathematically we state that we find the parameters x that solve the inverse problem G(x) = d using the Nelder-Mead direct search method to maximize the log-likelihood of the data.…”

Section: Experimental Methodsmentioning

confidence: 99%

Electro-drop bouncing in low-gravity

Schmidt

Weislogel

2020

Physics of Fluids

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We investigate the dynamics of spontaneous jumps of water drops from electrically charged superhydrophobic dielectric substrates during a sudden step reduction in gravity level. In the brief free-fall environment of a drop tower, with a non-homogeneous external electric field arising due to dielectric surface charges (with surface potentials 0.4-1.8 kV), body forces acting on the jumped drops are primarily supplied by polarization stress and Coulombic attraction instead of gravity. This electric body force leads to a drop bouncing behavior similar to well-known phenomena in 1-g 0 , though occurring for much larger drops (∼ 0.5 mL). We show a simple model for the phenomenon, its scaling, and asymptotic estimates for drop time of flight in two regimes: at short-times close to the substrate when drop inertia balances Coulombic force due to net free charge and image charges in the dielectric substrate and at long-times far from the substrate when drop inertia balances free charge Coulombic force and drag. The drop trajectories are controlled primarily by the dimensionless electrostatic Euler number Eu, which is a ratio of inertial to electrostatic forces. To experimentally determine values of Eu we conduct a series of drop tower experiments where we observe the effects of drop volume, net free charge, and static surface potential of the superhydrophobic substrate on drop trajectories. We use a direct search optimization to obtain a Maximum Likelihood Estimate for drop net charge, as we do not measure it directly in experiment. For φEu/8π > 1 drops escape the electric field, where φ is a drop to substrate aspect ratio. However, we do not observe any escapes in our dataset. With an eye towards engineering applications I am also greatly indebted to Andrew Greenberg for his frequent and sage technical advice, and to Joe Shields for his assistance with drop tower experiments.

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“…14 Finally, it was shown that the electric conduction in PET obeys the Poole-Frenkel law in agreement with published data. 21,22 Theoretical models for CC measurements are already available and described in the literature 12 for several cases such as free charge injection and charge injection in the presence of trapping. Such models were originally applied to corona charging measurements under open circuit but they are the same for closed circuit measurements.…”

Section: Discussionmentioning

confidence: 99%

“…The advantage of the CC is that the Maxwell total current equation can be, in some cases, analytically integrated and the charge transport and trapping in insulators may be theoretically treated. 9,12 The connection between the CC and voltage methods is briefly discussed in Ref. 13.…”

Section: Introductionmentioning

confidence: 99%

Electric measurements with constant current: A practical method for characterizing dielectric films

Giacometti

Wisniewski

Ribeiro

et al. 2001

Review of Scientific Instruments

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This article assesses the use of the constant current ͑CC͒ method for characterizing dielectric films. The method is based on charging the sample with a constant current ͑current stress͒ and measuring the corresponding voltage rise under the closed circuit condition. Our article shows that the CC method is an alternative to the constant voltage stressing method to study the electric properties of nonpolar, ferroelectric, and polar polymers. The method was tested by determining the dielectric constant of polytetrafluoroethylene, and investigating the electric conduction in poly͑ethylene terephthalate͒. For the ferroelectric polymer poly͑vinylidene fluoride͒, it is shown that hysteresis loops and the dependence of the ferroelectric polarization on the electric field can be obtained.

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Corona charging of electrets: models and results

Cited by 40 publications

References 74 publications

Direct observation of the spatial distribution of charges on a polypropylene fiber via Electrostatic Force Microscopy

Direct observation of the spatial distribution of charges on a polypropylene fiber via Electrostatic Force Microscopy

Electro-drop bouncing in low-gravity

Electric measurements with constant current: A practical method for characterizing dielectric films

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