Dynamic molecular mobility of polyurethane by a broad range dielectric and mechanical analysis

Dupenne, David; Roggero, Aurélien; Dantras, Éric; Lonjon, Antoine; Pierre, T.; Lacabanne, C.

doi:10.1016/j.jnoncrysol.2017.04.022

Cited by 16 publications

(14 citation statements)

References 58 publications

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“…In other polymer families, however, charge transport processes are decoupled from the molecular mobility, resulting in an Arrhenius dependence of DC conductivity (e.g. silicones [30] or polyurethane [31] networks). Annealing the sample results in a three decade loss in dc con ductivity compared to the first BDS pass.…”

Section: Charge Transport Processes At Low Frequenciesmentioning

confidence: 99%

Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 1. Dielectric spectroscopy response in the dry state

Roggero

Caussé

Dantras

et al. 2019

Electrochimica Acta

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OATAO is an open access repository that collects the work of some Toulouse researchers and makes it freely available over the web where possible. This is an author's version published in: https://oatao.univ-toulouse.fr/23151Official URL : https://doi.Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 1. Dielectric spectroscopy response in the dry state. a b s t r a c tIn this series, an epoxy varnish for the corrosion protection of carbon steel was analyzed in the dry state by broadband dielectric spectroscopy (part 1) to describe the molecular mobility of the epoxy network. Electrochemical impedance spectroscopy measurements were then performed during immersion in a 0.5 M NaCl solution (part 2), with the intent to detect the signature of the molecular mobility in the wet state. The present part 1 focuses on the analysis of the dipolar relaxation times associated with the dielectric manifestation of the glass transition in the dry varnish (a mode). They displayed the charac teristic Vogel Fulcher Tammann dependence on temperature, which is the typical signature of the a mode. The study of the relaxation times showed an anti plasticizing process upon heating the sample, attributed to the outgassing of absorbed ambient humidity and plasticizers from the formulation. When these elements were completely removed, through an annealing step, the epoxy network became sta bilized. The low frequency electrical conductivity of the varnish presented a very similar temperature dependence to the a mode, meaning that the molecular mobility governs the electrical charge transport processes in this system. Absorbed ambient humidity and plasticizers also had a great influence on the electrical conductivity, resulting in three decades higher values compared to the annealed sample without these elements. The strong influence of plasticizers on both the molecular mobility (through plasticization) and the electrical conductivity should be taken into account in view of the barrier properties of the final coating. Part 1 of this series provides a basis for a molecular mobility analysis of the electrochemical impedance measurements performed in part 2.

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Section: Charge Transport Processes At Low Frequenciesmentioning

confidence: 99%

Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 1. Dielectric spectroscopy response in the dry state

Roggero

Caussé

Dantras

et al. 2019

Electrochimica Acta

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“…It indicates ions accumulation at electrode‐sample interfaces 27 . The value of

∆ ε_{KK}^{''}

for the

α

relaxation is higher (Table 3) than the one generally obtained for polymer matrices (around 10 −1 ) 47–49 …”

Section: Resultsmentioning

confidence: 79%

Dynamic electrical and mechanical properties of epoxy/silver nanowires composites

Bedel

Lonjon

Dantras

et al. 2021

J of Applied Polymer Sci

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The aim of this work is to study electrically conductive composites from an epoxy matrix loaded with silver nanowires (AgNWs). Dynamic mechanical analysis (DMA) and dynamic dielectric spectroscopy (DDS) were used to study the molecular mobility of the epoxy matrix and its epoxy/AgNWs composites. The influence of the epoxy/amine ratio on the macroscopic properties was analyzed. The loss modulus of the epoxy matrix highlights two major relaxations, β and α. The β relaxation is due to the localized mobility initiated by hydroxyl groups. The α trelaxation is the anelastic effect liberated at the glass transition. The introduction of a small amount of AgNWs (<8 vol%) has practically no influence on the mechanical properties of the glassy state. For the rubbery state, AgNWs cause an increase in the storage modulus as a function of the filler content. The loss modulus profile is modified: The 0.25emω relaxation due to heterogeneities of the 3D network is observed independently from the hydration level of composites. The magnitude of the α mode is increased due to the stick–slip phenomenon. Moreover, it is shifted toward lower temperatures upon the introduction of AgNWs. In other words, the activation enthalpy decreases for both modes. Electrical study through DDS and conductivity measurement of epoxy/AgNWs composites shows the consequence of a lower relative degree of conversion caused by the insertion of AgNWs. Epoxy/AgNWs composites allow us to obtain one of the highest values of the electrical conductivity for polymer‐based composites without any drastic evolution of mechanical properties.

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“…To characterize the low‐temperature relaxation process (the Schatzki dipolar process, 41 also labeled as γ‐process), the Havriliak‐Negami (HN) empirical model, was employed. For each sample, the four HN fitting parameters ( Δε , a , b and τ ) were determined, at several temperatures, from a multiple nonlinear regression analysis of the experimental isotherms of loss permittivity (ε″).…”

Section: Resultsmentioning

confidence: 99%

Effect of chain extender on the morphology, thermal, viscoelastic, and dielectric behavior of soybean polyurethane

Favero

Marcon

Figueroa

et al. 2021

J of Applied Polymer Sci

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The objective of this work was to determine the influence of different chain extenders (CEs) on the morphology, thermal, viscoelastic, and dielectric properties of soybean polyurethane (PU). The PU with ethane‐1.2‐diol showed a more organized structure, which was attributed to the smaller amount of methylene groups (CH2) and the shorter distance between the hydrogen bonds. While, PUs with dipropylene glycol, the free volume increased due to the less effective interactions formed between the hard and soft domains. The α, β, and γ transitions dipolar by conductive process, are probably associated with (a) local motions of the main chain, (b) the smaller groups rotation motions in the fatty acid chains in the soft phase, and (c) the CH2 group rotation motion in the amorphous region. The phase‐separated morphology is most evident at high temperatures due to the Maxwell–Wagner–Sillars interfacial polarization process.

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Dynamic molecular mobility of polyurethane by a broad range dielectric and mechanical analysis

Abstract: OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.

Cited by 16 publications

References 58 publications

Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 1. Dielectric spectroscopy response in the dry state

Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 1. Dielectric spectroscopy response in the dry state

Dynamic electrical and mechanical properties of epoxy/silver nanowires composites

Effect of chain extender on the morphology, thermal, viscoelastic, and dielectric behavior of soybean polyurethane

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