Impurity Effect of the Dielectric Properties of Isotactic Polypropylene

Umemura, Tokihiro; Suzuki, Takaya; Kashiwazaki, T.

doi:10.1109/tei.1982.298498

Cited by 41 publications

(15 citation statements)

References 9 publications

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“…b relaxation. Activation energies for this process usually range from 90 to 170 kJ mol -1 [7,22], but much higher values (up to 350 kJ mol -1 ) are also reported [4]. The intermediate b peak situated around 300 K has been attributed to the glass transition of the amorphous phase.…”

Section: Resultsmentioning

confidence: 97%

“…The intermediate b peak situated around 300 K has been attributed to the glass transition of the amorphous phase. Due to the broadness of this relaxation, some authors proposed two transitions involving unconstrained regions of the amorphous phase and regions constrained by crystallites (which may depend on the crystallite size [22]) [4,7]. The Vogel-Fulcher-Tammann (VTF) or its equivalent, the Williams-Landel-Ferry temperature dependence observed for this relaxation indicates cooperative behaviour related to the glass transition [41][42][43].…”

Section: Resultsmentioning

confidence: 99%

“…The measurable dielectric relaxations and losses in apolar PP are generally ascribed to impurities and to the fact that it is always slightly oxidized and thus contains polar carbonyl, peroxy or hydroperoxy groups. Among impurities, residual catalysts and antioxidants have been reported to affect the dielectric properties [4]. However, for the electrical application of such polymers, it is of essential interest to understand the dielectric phenomena in them.…”

Section: Introductionmentioning

confidence: 99%

“…The origins of these relaxations have been studied in the past, mainly by mechanical measurements. However, a few dielectric studies are also available [4,[9][10][11]. Although some detailed molecular assignments are still open to debate, the reality of the basic relaxation processes is clear.…”

Section: Introductionmentioning

confidence: 99%

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Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

Suljovrujić

2012

Polym. Bull.

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The molecular relaxation behaviour of isotactic polypropylene (iPP) exposed to gamma radiation in air to various absorbed doses (up to 700 kGy) has been investigated by dielectric loss (tan d) analysis; the polar (mainly carbonyl and hydroperoxide) groups that were introduced by radiation-induced oxidation were considered as tracer groups. All relaxation zones (a, b, c and d in the order of decreasing temperature), between 25 K and melting temperature, were studied in the frequency range from 1 kHz to 1 MHz. The changes observed in the dielectric relaxation spectra were related to the modifications in the structural and morphological parameters attributed to exposure of the iPP samples to radiation. Wide-angle X-ray diffraction was used to investigate radiation-induced changes in the crystalline structure and degree of crystallinity, since the a relaxation is connected with this phase. Infrared spectroscopy and gel measurements were used to determine the changes in the oxidative degradation and the degree of network formation, respectively. Conclusions derived using different methods were compared. This study reveals high dielectric and/or relaxation sensitivity of iPP to gamma radiation. Disappearance of the lowtemperature dielectric (c and d) relaxations together with large changes in intensity, position and activation energy of the dielectric a relaxation are observed with gamma irradiation and are mainly connected with oxidative degradation in iPP structure.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

Suljovrujić

2012

Polym. Bull.

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“…PP is a n essentially apolar material with a low inherent dipole moment (4). exhibiting dielectric relaxation peaks mainly as a consequence of slight oxidation and/or the presence of small amounts of polar additives (8). In the audio frequency range, PP shows two dielectric loss peaks in the temperature range covered in the present study.…”

Section: Discussionmentioning

confidence: 51%

AC and DC dielectric properties of some polypropylene/calcium carbonate composites

Bánhegyi

Karasz

Petrovìć³

1990

Polymer Engineering & Sci

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AC dielectric properties and thermally stimulated polarization (TSP) and depolarization (TSD) currents were studied in a series of CaCO3‐filled polypropylene composites. The filler content (0 to 50 weight percent) and the average particle size (3.0 to 16.1 μm) at constant filler content (30 weight percent) were varied in separate groups of samples. In a third group of samples the filler (20 to 40 weight percent) was surface treated with stearates. The AC dielectric behavior of composites containing untreated fillers is largely determined by a small amount of adsorbed water. Upon heating, the dielectric properties show maxima (increasing with decreasing frequency) which disappear on cooling. In the case of stearate‐treated fillers the dielectric loss level is higher, the dispersion and loss curves on heating reflect a combination of dipolar and protonic processes with water desorption. In the dry state the onset of an audio frequency relaxation process is observed in the pre‐melting zone. The thermally stimulated currents of the composites containing treated and untreated fillers are also different. In the case of the untreated fillers the TSP curves show maxima indicating water desorption which are increasingly intense and roughly exponential with filler content. The high temperature conductivity and the intensity of the pre‐melting depolarization peak pass through a minimum as a function of filler content. Above 20 weight percent filler content the activation energy of high temperature conductivity decreases. In the case of the surface treated samples, the thermally stimulated response is different for “wet” and dried samples. The dry samples exhibit a relaxation between the amorphous and crystalline transitions of the matrix polymer which is probably due to interfacial relaxation caused by the enhanced surface conductivity of the stearate‐treated fillers.

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Polymer Dielectrics for Capacitor Application

Nasreen

Treich

Baczkowski

et al. 2017

Kirk-Othmer Encyclopedia of Chemical Technology

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Dielectric materials are a class of materials that are polarized under an electric field. Typically, highly polarizable, or high dielectric materials are used in energy storage applications such as a capacitor. Materials that have high dielectric constant, low dielectric loss, and high breakdown strength, have high energy density. Other important criteria for choosing a dielectric candidate include good thermal and mechanical stability. For their ease of processability and light weight applications, many polymer dielectrics are currently used commercially. Moreover, research to discover new materials to meet growing demand for lighter and more efficient materials has been ongoing. This article provides information on the basic principles of a capacitor, what makes a good dielectric material for capacitor energy storage applications, common dielectric polymers and their properties, as well as the exploration of next generation dielectric materials. Finally, an examination of current efforts to explore new dielectric materials and how they can be further tuned with the help of theoretical computations and experimental validation, are discussed.

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Impurity Effect of the Dielectric Properties of Isotactic Polypropylene

Cited by 41 publications

References 9 publications

Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

AC and DC dielectric properties of some polypropylene/calcium carbonate composites

Polymer Dielectrics for Capacitor Application

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