Electret stability related to spherulites in polypropylene

Thyssen, A.; Almdal, Kristoffer; Thomsen, Erik Vilain

doi:10.1109/tdei.2015.004891

Cited by 13 publications

(13 citation statements)

References 14 publications

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“…Figure 3 shows the surface potential after 24 hours as a function of the crystallinity for the different sample types. The solid lines represent data from Figure 1 to Figure 4 and the dashed lines represent data from previous work [8]. In Figure 3, a clear correlation is seen between increased charge stability and an increased degree of crystallinity.…”

Section: Crystallinitymentioning

confidence: 77%

“…We emphasize the importance of the small size of the spherulites [8]. The size of the spherulites was determined using SEM to be smaller than 1 µm.…”

Section: Resultsmentioning

confidence: 99%

“…After the samples have been pressed, they are exposed to quenching in an ice bath, going from 180 °C to 0 °C in approximately 1 s. This is to ensure small size spherulites, which work done previously [8] concluded was very important to obtain a good charge stability.…”

Section: Press and Coolingmentioning

confidence: 99%

“…The higher the degree of crystallinity the better the charge stability will be. However, since the size of the crystalline areas, known as spherulites, plays an even bigger role than the crystallinity [8], increasing the crystallinity should not happen through increased spherulites size but through an increased number spherulites.…”

Section: Crystallinitymentioning

confidence: 99%

“…In reference [6], [7] it has been revealed that the electrical charges in polymer electrets are associated with the crystalline spherulites, in particular the center of these. In [8] we have demonstrated that the size of the spherulites are of major importance to the charge stability. The influence of the degree of crystallinity is, however, to be determined.…”

Section: Introductionmentioning

confidence: 96%

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Electret stability related to the crystallinity in polypropylene

Thyssen

Almdal

Thomsen

2017

IEEE Trans. Dielect. Electr. Insul.

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Through mixing isotactic-polypropylene (i-PP) and atactic-polypropylene (a-PP), we have demonstrated the importance of the crystallinity in polypropylene as an electret material. Samples with crystallinities between 7 % and 47 % were used. A high degree of crystallinity in polypropylene, used as an electret, gives a better charge stability with respect to temperature and humidity changes. The semicrystalline i-PP significantly outperforms a-PP regarding charge stability. a-PP is an amorphous polymer. By mixing a-PP and i-PP, the degree of crystallinity can be controlled, while all other sample preparation processes and characteristics can be identical. This is important since the performance of an electret material is sensitive to its previous process history. Activation energies used for predicting the thermal potential decay are determined from thermally stimulated current and isothermal potential decay experiments. Activation energies from 0.98 eV to 1.41 eV were determined. From these values, a very good agreement was achieved between the experimental potential decay at room temperature for more than 290 days, and a theoretical estimation of the potential decay.

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Section: Crystallinitymentioning

confidence: 77%

“…We emphasize the importance of the small size of the spherulites [8]. The size of the spherulites was determined using SEM to be smaller than 1 µm.…”

Section: Resultsmentioning

confidence: 99%

Section: Press and Coolingmentioning

confidence: 99%

Section: Crystallinitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 3 more Smart Citations

Electret stability related to the crystallinity in polypropylene

Thyssen

Almdal

Thomsen

2017

IEEE Trans. Dielect. Electr. Insul.

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Study on correlation of filtration performance and charge behavior and crystalline structure for melt‐blown polypropylene electret fabrics

Xiao

Gui

Chen

et al. 2015

J of Applied Polymer Sci

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Melt-blown polypropylene (PP) electret fabrics are widely used as air filter media due to the specific mechanism of electrostatic filtering. In this article, two additives, stearate and modified rosin, are doped to PP fabrics during melt-blown process. The filtration performance of doped PP gets improved greatly, with filtration efficiency increased by 6% at room temperature but its temperature stability promoted dramatically. As a result, the filtration efficiency of doped PP still remains above 95% of its initial, whereas that of non-doped PP only remains 58% at 1108C. By XRD characterization the structure modification is observed after doping. The crystallinity increases from 14.17% to 22.64% and 29.62%, respectively. Meanwhile, the crystallite has a smaller size, respectively, 89Å and 86Å as compared to 107Å for non-doping in the direction vertical to lattice plane (110). This demonstrates that additive doping can give rise to larger crystallinity and more fine-grained crystallite. Therefore, doped PP improves its charge storage behavior ascribing to expanding interface between crystallite and amorphous region and then enlarging charge trap density. Furthermore, the effect of additive doping on electret charge storage behavior is investigated by short-circuit TSD, and the filtration performance can be explained relevantly with TSD. A charge storage profile is also adopted to illustrate that the space charge captured by charge traps is in the form of space-charge dipole with the rigidity of crystallite.

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Annealing for the improvement of the capabilities of parylene C as electret

Kachroudi

Lagomarsini

Mareau

et al. 2018

J of Applied Polymer Sci

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Parylene C is a polymer elaborated by chemical vapor deposition and is particularly useful for the coating of deformed structures. New‐generation soft energy harvesting electrostatic generators can be of complex shape. These generators need electret material in order for them to function. It could thus be interesting to incorporate parylene C in this device. However, this polymer suffers from bad retention of trapped charges after corona discharge and a poor thermal stability of these charges. In this work, parylene C polymers were subjected to specific annealing before corona charging. This induces strong changes in the crystallinity of the material. Atomic force microscopy and X‐ray diffraction quantified the crystalline nature of parylene C following the annealing temperature. Surface potential decay of corona‐charged parylene C demonstrated that annealing to about 150°C is beneficial for the trapping of charges for a long time (analysis over 12 days). At the same time, thermal stability of the electret parylene C is achieved up to 100°C. Spherulites with a specific area close to the surface of the polymer could explain such performances due to their influence on the distribution of traps. Dielectric analysis does not confirm that the decay of surface charges is correlated to the dynamics of polymer chains, although the moving of chains probably influences the flowing of these charges. In sum, annealed parylene C appears to be a new interesting candidate for electret‐based electrostatic generators. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46908.

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Electret stability related to spherulites in polypropylene

Cited by 13 publications

References 14 publications

Electret stability related to the crystallinity in polypropylene

Electret stability related to the crystallinity in polypropylene

Study on correlation of filtration performance and charge behavior and crystalline structure for melt‐blown polypropylene electret fabrics

Annealing for the improvement of the capabilities of parylene C as electret

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