Influence of ionizing irradiation on the electrical strength of polyolefines and their blends with elastomers

Магеррамов, А. М.; Никольский, В.Г.; Mironov, N.A.; Bagirov, M. A.; Chebotarevskii, A.E.

doi:10.1016/0032-3950(81)90412-3

Cited by 2 publications

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“…By now, various mechanisms have been proposed for changes in the electrophysical and strength properties of polyolefins, among them reversible and irreversible free radical processes under exposure to γ-radiation [6][7][8][9][10][11]16]. The electric strengthening of polymers and the mechanisms of this effect are of considerable importance.…”

Section: Resultsmentioning

confidence: 99%

“…It is well known [3][4][5] that polyethylene (PE) is a preferably crosslinkable polymer, whereas PP is prone to oxidative degradation. Changes in the electric and dielectric properties upon radiation modification strongly depend on polymer crystallization conditions and irradiation mode [2,6]. Certain doses of γ -radiation on PE and PP lead to an increase in the electric strength E st [4][5][6][7] and to changes in the dielectric loss tangent , permittivity ε [8], electric conductivity [9], charge state [10], and mechanical strength [1,11].…”

mentioning

confidence: 99%

“…Changes in the electric and dielectric properties upon radiation modification strongly depend on polymer crystallization conditions and irradiation mode [2,6]. Certain doses of γ -radiation on PE and PP lead to an increase in the electric strength E st [4][5][6][7] and to changes in the dielectric loss tangent , permittivity ε [8], electric conductivity [9], charge state [10], and mechanical strength [1,11]. These changes in the dielectric properties of polymers are primarily associated with crosslinking, oxidation, degradation, and reversible and irreversible processes.…”

mentioning

confidence: 99%

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Structural aspects of the radiation modification of the dielectric properties of polyolefins

Магеррамов

Dashdamirov

2005

High Energy Chem

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1 A wide variety of supermolecular structure elements in polyolefins, in particular, low-density polyethylene (LDPE), high-density polyethylene (HDPE), and isotactic polypropylene (PP), provides prerequisites to the target-oriented and efficient modification of their structure and electric properties by γ -or electron-beam irradiation [1,2]. It is well known [3][4][5] that polyethylene (PE) is a preferably crosslinkable polymer, whereas PP is prone to oxidative degradation. Changes in the electric and dielectric properties upon radiation modification strongly depend on polymer crystallization conditions and irradiation mode [2,6]. Certain doses of γ -radiation on PE and PP lead to an increase in the electric strength E st [4][5][6][7] and to changes in the dielectric loss tangent , permittivity ε [8], electric conductivity [9], charge state [10], and mechanical strength [1,11]. These changes in the dielectric properties of polymers are primarily associated with crosslinking, oxidation, degradation, and reversible and irreversible processes. Note that the supermolecular structure and crystallization conditions of a polymer can affect the kinetics and direction of these processes. In this case, it is of importance to refine the roles of the crystalline phase and the size of crystallites, spherulites, and individual elements of the polymer supermolecular structure. For example, according to published data [12], treelike tracks branched under exposure to an electric field developed in crosslinked PE along the lamellar structure, whereas the development of a fine spherulitic structure with a high crystallinity in PP improved the electret properties of the polymer [13]. However, the possible influence of transient species (ions, radicals, and geminate and bound pairs) and bulk and polarization effects on the electrophysical, service, and strength properties of PE and PP were not discussed in the liter-1 E-mail: arifm50@rambler.ru δ tan ature. Of the performance characteristics, the electric strength E st and the mechanical strength σ m of polymers and compositions are the most important. At high fields (close to prebreakdown fields) in PE, the processes of strength losses are preceded by free-radical states [14]. Free radicals as electron traps affect radiation-induced electric conductivity [9,15]. At the same time, taking into account structure relaxation, elementary ion-radical reactions, etc., in polyolefins during γ -irradiation could reveal other conceivable reasons for the effect of electric strengthening and changes in the parameters ε and . The mechanisms of the radiation-induced oxidative degradation of PP [14] and the role of intermolecular and intramolecular crosslinks, excited and ionic states, posteffects, and radical formation in the radiation modification of structures and properties are not clearly understood. In combined effects on polymers, synergistic [16] and antagonistic effects [17] were not taken into consideration. The study of these problems in the structure-property-technology aspect is of gre...

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Section: Resultsmentioning

confidence: 99%