Complete relaxation map of polyethylene: filler-induced chemical modifications as dielectric probes

Frübing, Peter; Blischke, D.; Gerhard, Reimund; Khalil, M.S.

doi:10.1088/0022-3727/34/20/308

Cited by 75 publications

(31 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The VFT parameters are evaluated by fitting equation (2) to the experimental results obtained for β-relaxation in the POM/alumina system and are listed in Table I. The VFT temperature dependence of the loss maxima in the case of β-relaxation indicates a cooperative character of the corresponding relaxation mechanisms, which is typical behavior for mechanisms related to the glass to rubber transition of the amorphous phase [5,42]. This result confirms the initial hypothesis of ours that β-relaxation, recorded only in the POM/alumina system, is related to the glass to rubber transition of POM.…”

Section: Resultsmentioning

confidence: 99%

Dielectric relaxations in polyoxymethylene and in related nanocomposites: Identification and molecular dynamics

Karahaliou

Kerasidou

Georga

et al. 2014

Polymer

View full text Add to dashboard Cite

Broadband dielectric spectroscopy is employed for the study of the dielectric response of Polyoxymethylene/boehmite alumina (POM/alumina) and Polyoxymethylene/Layered Silicates (POM/LS) semi-crystalline nanocomposites, together with the response of pure POM. The compilation of the dielectric responses of all systems reveals the existence of five dielectric relaxation mechanisms assigned, in terms of decreasing temperature at constant frequency, as IP (interfacial polarization), α-, 2 β-, γ-and δ-relaxations. IP, α-and γ-relaxations are detected in all studied systems and they are well documented in the literature. δ-relaxation, been the fastest mechanism, is present only in the POM/LS system and is associated with defect dipoles in the crystalline phase of POM. Finally, β-relaxation is present only in the POM/alumina nanocomposite and its dynamics obey Vogel-Fulcher-Tamann temperature dependence. This work presents a complete mapping of the dielectric relaxation mechanisms of POM and signifies the connection of β-mode with the glass to rubber transition of POM, confirming its cooperative character.

show abstract

Section: Resultsmentioning

confidence: 99%

Dielectric relaxations in polyoxymethylene and in related nanocomposites: Identification and molecular dynamics

Karahaliou

Kerasidou

Georga

et al. 2014

Polymer

View full text Add to dashboard Cite

show abstract

“…, B and the Vogel temperature T ? are VTF parameters [46]. The Vogel temperature is closely related to the dynamic glass-transition temperature T g , which is usually defined as the temperature where the relaxation time is s = 100 s. The VTF parameters are also used for determining the dynamic fragility m and the apparent activation energy E a at T g [43]; the values of the calculated parameters are given in Table 1.…”

Section: Resultsmentioning

confidence: 99%

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

Suljovrujić

2012

Polym. Bull.

View full text Add to dashboard Cite

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.

show abstract

“…The Vogel temperature is known to be closely related to the dynamic glass transition temperature T g which is usually defined as the temperature where the relaxation time is 100 s. 28,46 The VFTH fit parameters 0 , T 0 and T V of the relaxation as well as the glass transition temperature T g are listed in Table 2 for the two conditions. It is clear that the water influences the cooperative process and the glass transition estimated from the VFTH is around 8 K, higher in dry sample compared to the wet one.…”

Section: Dielectric Relaxation Mapmentioning

confidence: 99%

Change in dielectric relaxation with the presence of water in highly filled composites

Tuncer

2017

J. Adv. Dielect.

View full text Add to dashboard Cite

It is important to determine the dielectric characteristics of semiconductor encapsulation materials based on epoxy resins. We employed the dielectric spectroscopy technique to investigate the dielectric relaxation in the presence of water and how it changes the relaxation. It was observed that the dielectric relaxation of the material was significantly influenced by absorbed water, the local segmental motion (also known as Johari-Goldstein ( ) relaxation) was influenced most by the presence of the water, it was modified by the wet sample compared to dry one, and required high activation energy. The relaxation related to the glass transition was contributed by the cooperative motion (the -relaxation) of the epoxy resin system. The -relaxation was shifted to a low temperature in the wet sample compared to dry one. The relaxation was modeled with a clear Vogel-Fulcher-Tammann-Hesse (VFTH) behavior; the Vogel temperature of the wet sample was 8 K lower than the dry sample. The presence of water acts as a plasticizer for the molecular relaxation, and speed-up the cooperative process. The measured data were also used to estimate the electrical properties of the resin system by employing an effective-medium model together with a porous media continuum model by taking into account the physical properties of the system. It is already known that the influence of water in semiconductor packaging is important in sensitive applications. The presented measurements and the analysis method would be appreciated within the semiconductor packaging community to improve material selection and performance evaluation efforts.

show abstract

Complete relaxation map of polyethylene: filler-induced chemical modifications as dielectric probes

Cited by 75 publications

References 16 publications

Dielectric relaxations in polyoxymethylene and in related nanocomposites: Identification and molecular dynamics

Dielectric relaxations in polyoxymethylene and in related nanocomposites: Identification and molecular dynamics

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

Change in dielectric relaxation with the presence of water in highly filled composites

Contact Info

Product

Resources

About