Time‐resolved nanosecond radiation‐induced conductivity in polymers

Tyutnev, A. P.; Abramov, V. N.; Dubenskov, P. I.; Saenko, V. S.; Ванников, А. В.; Pozidaev, E. D.

doi:10.1002/actp.1986.010370603

Cited by 20 publications

(10 citation statements)

References 36 publications

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“…Currently, these works are of historical interest only (see [24][25][26][27]). This early effort found logical conclusion in our works [9,28]. The last article dealt with pulsed (8, 40 ns and 0.3 ms) RIC data for a broad polymer list reporting values of K p .…”

Section: Discussionmentioning

confidence: 59%

“…The last article dealt with pulsed (8, 40 ns and 0.3 ms) RIC data for a broad polymer list reporting values of K p . Furthermore, for the first time, we proposed an RFV treatment of pulsed irradiations that introduces the notion of the initial effective mobility µ in = α 1+α µ 0 τ 0 ν 0 [28]. In addition, we developed a simple analytic approach to estimate the frequency factor itself.…”

Section: Discussionmentioning

confidence: 99%

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Time-Resolved Radiation-Induced Conductivity of Polyimide and Its Description Using the Multiple Trapping Formalism

et al. 2019

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Polymer dielectrics subjected to intense radiation fluxes exhibit a radiation-induced conductivity (RIC). Polyimide is a good dielectric with excellent mechanical and thermal properties featuring high radiation resistance currently widely used in the spacecraft industry. Its RIC has been extensively studied in several laboratories. The purpose of the present study is to make a direct measurement of the RIC for both pulsed and continuous irradiation using a current sensing technique, which is contrary to the indirect method employing a surface-potential decay technique that is now preferred by spacecraft charging engineers. Our experiments are done in a small-signal regime excluding any recombination and dose effects. In combination with existing computer codes, we managed to develop further the conventional multiple trapping formalism and the RIC theory based on it. The main idea is to supplement an exponential trap distribution responsible for a dominant dispersive carrier transport in polymers with a small concentration of inherent deep traps which may or may not have an energy distribution. In line with this reasoning, we propose a tentative set of RIC model parameters for polyimide that accounts for the observed experimental data. The findings and their implications are discussed in a broad context of previous studies.

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Section: Discussionmentioning

confidence: 59%

Section: Discussionmentioning

confidence: 99%

Time-Resolved Radiation-Induced Conductivity of Polyimide and Its Description Using the Multiple Trapping Formalism

et al. 2019

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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%

“…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 .…”

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.…”

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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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Chemical aspects of the radiation‐induced conductivity in polymers

1996

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It has been demonstrated that radiation-induced conductivity (RIC) is strongly dependent on the chemical structure ofthe macromolecules, this dependence being influenced by the position of the active molecular group acting as a hopping center for charge carriers: main chain vs pendant case. Both RIC magnitude and its nature (free ion vs geminate) are affected. Annealing of the radiation-induced conductivity (RIC) in four common polymers (PS, PET, LDPE and PTFE) continuously irradiated in vacuum to doses of about 5 x 10' Gy has been studied. While substantial recovery (up to 75%) has been observed in PS and PET, only steady degradation of RIC has been encountered in LDPE and especially in PTFE (annealing at elevated temperatures has been fulfilled only in air). Unlike other polymers tested, PS shows recovery that depends critically on the surrounding atmosphere (air or vacuum).To describe these results one relies heavily on the radiation-induced oxidation as a chain radical process with degenerate branching (a case of LDPE and PTFE) and catalytic recombination of macroradicals (as in PS).

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Time‐resolved nanosecond radiation‐induced conductivity in polymers

Cited by 20 publications

References 36 publications

Time-Resolved Radiation-Induced Conductivity of Polyimide and Its Description Using the Multiple Trapping Formalism

Time-Resolved Radiation-Induced Conductivity of Polyimide and Its Description Using the Multiple Trapping Formalism

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

Chemical aspects of the radiation‐induced conductivity in polymers

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