A dielectric study of molecular relaxations in irradiated high density polyethylene

Stamboliev, G.; Suljovrujić, E.

doi:10.1016/j.polymdegradstab.2009.12.010

Cited by 14 publications

(7 citation statements)

References 49 publications

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“…At this temperature, the chain displacement is several nm per second and can occur between amorphous and crystalline regions. Such a picture is in good relationship with the transition temperature range at SANS measurements and the dynamic of α-relaxation of the neat HDPE sample from temperature-dependent dielectric measurements [69,70]. These transformations in the nanoscale level give a new insight into the changes in mechanical properties (e.g., tensile strength [71]) observed in some quenched composites after mild annealing.…”

Section: Thermal Stability Of the Polymer Nanocomposite Structuresupporting

confidence: 54%

Composite Films of HDPE with SiO2 and ZrO2 Nanoparticles: The Structure and Interfacial Effects

et al. 2021

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Herein, we investigated the influence of two types of nanoparticle fillers, i.e., amorphous SiO2 and crystalline ZrO2, on the structural properties of their nanocomposites with high-density polyethylene (HDPE). The composite films were prepared by melt-blending with a filler content that varied from 1% to 20% v/v. The composites were characterized by small- and wide-angle x-ray scattering (SAXS and WAXS), small-angle neutron scattering (SANS), Raman spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). For both fillers, the nanoaggregates were evenly distributed in the polymer matrix and their initial state in the powders determined their surface roughness and fractal character. In the case of the nano-ZrO2 filler, the lamellar thickness and crystallinity degree remain unchanged over a broad range of filler concentrations. SANS and SEM investigation showed poor interfacial adhesion and the presence of voids in the interfacial region. Temperature-programmed SANS investigations showed that at elevated temperatures, these voids become filled due to the flipping motions of polymer chains. The effect was accompanied by a partial aggregation of the filler. For nano-SiO2 filler, the lamellar thickness and the degree of crystallinity increased with increasing the filler loading. SAXS measurements show that the ordering of the lamellae is disrupted even at a filler content of only a few percent. SEM images confirmed good interfacial adhesion and integrity of the SiO2/HDPE composite. This markedly different impact of both fillers on the composite structure is discussed in terms of nanoparticle surface properties and their affinity to the HDPE matrix.

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Section: Thermal Stability Of the Polymer Nanocomposite Structuresupporting

confidence: 54%

Composite Films of HDPE with SiO2 and ZrO2 Nanoparticles: The Structure and Interfacial Effects

et al. 2021

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“…Comparable behaviour has also been reported for severely aged LDPE [58] and HDPE [59]. Elsewhere, Suljovrujic [60] suggested that such a dielectric response may be related to the mobility of polar chains segments or disordered chains located in amorphous regions (the dielectric β and γ-relaxation) and at the surface of crystalline regions (α and γ-relaxation) [59], such that the relaxation shifts to higher frequencies with increasing amorphous fraction (see aged LDPE and HDPE). In the case of the polyethylene blend system considered here, the broad dielectric relaxation peaks located at frequencies above 1 Hz in figure 7(b) are therefore in line with published data and readily explicable in terms of various moieties/defects (cleaved chains, crosslinks, C=O, O-H and C=C) located at a range of different structural locations within the polymer morphology.…”

Section: Dielectric Responsementioning

confidence: 82%

On the influence of morphology and chemical defects on charge transport dynamics in polyethylene: thermal ageing and concentration gradient

Tantipattarakul¹,

Vaughan²,

Andritsch³

2019

J. Phys. D: Appl. Phys.

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A blend composed of a high-density polyethylene and a low-density polyethylene was subjected to thermo-oxidative ageing at 160 °C, under conditions where oxygen diffusion effects lead to a non-uniform distribution of chemical defects throughout the specimens. The existence of highly and lightly oxidised regions was demonstrated by Fourier transform infrared spectroscopy and confocal Raman microprobe spectroscopy and the effect of these on the dielectric behaviour of the system was investigated. Dielectric spectroscopy revealed a broad loss peak at frequencies above 1 Hz that increases in strength with increasing ageing time, which we associate with the motion of polar chain segments within the polymer. For ageing times below 3 h, samples exhibited reduced conductivity under a constant electric field compared with the initial unaged system; above 3 h, the conductivity was found to increase monotonically with ageing time and corresponded to the appearance of an additional low frequency (<1 Hz) dielectric loss process and marked migration of space charge into the bulk away from the relevant physical electrode. This change in behaviour was found to occur abruptly and the final distribution of space charge was found to correlate well with the distribution of ageing inducing chemical defects within the system. From these observations, the effects of chemical defects on charge transport dynamics are discussed.

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“…This observation holds for both bulk crystallized specimens and single crystal mats [47]. Thus, chemicrystallization that originates from the morphological rearrangement of polymer fragments after radiation-induced chain scission events [51] can introduce shift in the position and increase in apparent activation energy of the a relaxation, clearly observed for high-density polyethylene [52]. As a consequence of a branched molecular structure, LDPE has initially small crystallinity.…”

Section: A Ir Normalized Absorbance (A/d Values;mentioning

confidence: 74%

“…The constrained chains are unable to relax completely, thus the relaxation strength is reduced. Furthermore, complete disappearance of the b relaxation in HDPE with gamma irradiation, observed in our previous paper [52], is attributed to the more restricted chain segment mobility in the network, but the contribution of the radiation-induced increase in crystallinity was also taken into account. Also, according to Ratner et al [74] this transition in HDPE also disappeared upon peroxide-generated crosslinking in interlamellar regions.…”

Section: A Ir Normalized Absorbance (A/d Values;mentioning

confidence: 79%

Polyethylene crosslinked in different media: structural changes versus dielectric behaviour

et al. 2014

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Changes in the structure and dielectric properties of low-density polyethylene were created by gamma irradiation in air, deionised water and nitrogen. Role of irradiation media on dielectric and charge trapping behaviour was studied through dielectric loss and thermally stimulated discharge current measurements. Changes in magnitude, position and activation energy of all dielectric relaxations (c, b and a) were found to be dependent on crosslinking and oxidative degradation, two competitive processes which can be tuned by radiation dose and media. Largest changes in the position and activation energy were found for the b relaxation due to its cooperative nature.

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A dielectric study of molecular relaxations in irradiated high density polyethylene

Cited by 14 publications

References 49 publications

Composite Films of HDPE with SiO2 and ZrO2 Nanoparticles: The Structure and Interfacial Effects

Composite Films of HDPE with SiO2 and ZrO2 Nanoparticles: The Structure and Interfacial Effects

On the influence of morphology and chemical defects on charge transport dynamics in polyethylene: thermal ageing and concentration gradient

Polyethylene crosslinked in different media: structural changes versus dielectric behaviour

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