The nature of the gamma dielectric relaxation in diglycidyl ether Bisphenol-A (DGEBA) based epoxies

Saeedi, Istebreq A.; Chalashkanov, N. M.; Dissado, L.A.; Vaughan, A. S.; Andritsch, Thomas

doi:10.1016/j.polymer.2022.124861

Cited by 8 publications

(7 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In summary, the above results suggest that, over the temperature range considered, the behaviour of the system is moving away from activated tunnelling towards an Arrhenius behaviour. Similar behaviour was reported in [27], particularly in systems that contained moieties that enhanced molecular mobility. We, therefore, concur with the above suggestion that, in the context of Figure 4, "pure thermal activation, as described by the Arrhenius equation is [ .…”

Section: Arrhenius Activated Tunnellingsupporting

confidence: 78%

“…This showed that the data aligned well with both Arrhenius and activated tunnelling behaviour, with both methodologies giving physically reasonable parameter values. The significance of this analysis is that it further reinforces the assertion of [27] that "pure thermal activation, as described by the Arrhenius equation, is just a manifestation of activated tunnelling above some material dependent temperature".…”

Section: Discussionsupporting

confidence: 63%

“…From this, it is evident that the data conform well to the Arrhenius equation (R 2 value of 0.962). However, it is evident from the residuals that these are not randomly distributed around the best fit line and, consequently, as recently described in our latest work [27], the same data set was also analysed in terms of the activated tunnelling model of Hill and Dissado [28]. In short, the approach considers quantum mechanical tunnelling through a potential barrier of height ∆ between potential energy minima separated by a distance d 0 .…”

Section: The Lower Temperature Dielectric Relaxation (γ Mode)mentioning

confidence: 99%

See 2 more Smart Citations

On Molecular Dynamics and Charge Transport in a Flexible Epoxy Resin Network

et al. 2022

Self Cite

View full text Add to dashboard Cite

An epoxy based on diglycidyl ether of bisphenol A was reacted with a long-chain poly(oxypropylene diamine) hardener in the presence of an accelerator, resulting in a flexible epoxy network. Tensile properties were tested as a function of accelerator concentration. All systems exhibited high levels of extensibility, with strain at failure values in excess of 65%. Molecular dynamics in a formulation containing 10 phr of accelerator were then examined using dielectric spectroscopy over the temperature range of 103–433 K. At low temperatures, a molecular relaxation process (γ relaxation) was observed and shown to conform well to both the Arrhenius equation and activated tunnelling. A stronger relaxation appeared (203–303 K) just before the onset of charge transport, which dominated the behaviour at higher temperatures. The former takes an unusual bimodal form, which we consider a result of overlapping β and α relaxations, consequently termed αβ mode. Analysis of this mechanism revealed a Vogel–Fulcher–Tammann (VFT) behaviour. The temperature-dependent DC conductivity, σDC (deduced from the low-frequency charge transport contribution to εr″), also revealed VFT behaviour with an onset statistically equivalent to that of the αβ mode, therefore suggesting that charge transport, at this temperature regime, is strongly affiliated with cooperative molecular motion.

show abstract

Section: Arrhenius Activated Tunnellingsupporting

confidence: 78%

Section: Discussionsupporting

confidence: 63%

Section: The Lower Temperature Dielectric Relaxation (γ Mode)mentioning

confidence: 99%

See 1 more Smart Citation

On Molecular Dynamics and Charge Transport in a Flexible Epoxy Resin Network

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…On the one hand, they reduce the mobility of the main-chain moieties and branch/chain ends of the base polymer, which ultimately leads to a lower value of the dielectric constant. On the other hand, they cause the accumulation of additional charges due to the interphase effect of the filler particles dispersed in the volume of the resin [71,[94][95][96][97]. For low filling levels (low wt%) the first effect dominates, so the ability of the composite structure to accumulate charges decreases and the dielectric constant is lowered [95][96][97][98].…”

Section: Analysis and Discussion Of Resultsmentioning

confidence: 99%

“…The curing agent used for the resin is an aliphatic amine-based hardener with a weight ratio of 5:1 (resin to hardener). Epoxy resins of this type are commonly applied in the electrical industry, and their properties are well established [67][68][69][70][71][72][73]. The gelation time of the applied resin at 25 • C is approximately 35 min (2100 s).…”

Section: Experiments Description 21 Materials For Tested Samplesmentioning

confidence: 99%

Control of Dielectric Parameters of Micro- and Nanomodified Epoxy Resin Using Electrophoresis

Dąda,

Błaut,

Mikrut

et al. 2024

Energies

View full text Add to dashboard Cite

This work presents the results of research on submicro- and nanocomposites with gradient properties, produced in a planned electrophoretic process. Epoxy-resin-based samples were filled with TiO2 particles of three different sizes (13 nm, 38 nm, and <1 µm) at four different values of average electric field Eav (0.0 Vmm−1, 125 Vmm−1, 250 Vmm−1, and 500 Vmm−1) for 1 h each. Changes in selected dielectric parameters (dielectric constant εr and dielectric loss factor tanδ) of the composites were analyzed using broadband dielectric spectroscopy (10−1 Hz to 105 Hz). The influence of the Eav and the current i(t) flowing through the sample material and the Joule heat generated in it on the resin curing process and the final gradient of dielectric parameters were investigated. The results show that the degree of modification of the εr gradient increases with increasing Eav and is more pronounced in the case of TiO2 nanoparticles. The largest modifications in the εr and tanδ were obtained for nanoparticles with a diameter of 13 nm at Eav = 500 Vmm−1, while the lowest for particles < 1 µm at Eav = 125 Vmm−1. The effect of electrophoresis on the dielectric parameters is significant, especially near the anode region. Increasing the concentration of TiO2 particles at the anode occurs at the expense of reducing their concentration in the remaining volume of the sample. The test results clearly demonstrate the importance of particle dimension and electric field strength for the gradient modification of the properties of the epoxy composite using electrophoresis. Numerical simulations of electric field stresses in the epoxy resin during the electrophoresis process, performed in the COMSOL program, revealed a significant increase in the E field strength in the areas close to the anode and cathode.

show abstract

Modeling and simulation of shape memory nanocomposites

Kausar,

Ahmad

2024

Shape Memory Polymer-Derived Nanocomposites

View full text Add to dashboard Cite

The nature of the gamma dielectric relaxation in diglycidyl ether Bisphenol-A (DGEBA) based epoxies

Cited by 8 publications

References 37 publications

On Molecular Dynamics and Charge Transport in a Flexible Epoxy Resin Network

On Molecular Dynamics and Charge Transport in a Flexible Epoxy Resin Network

Control of Dielectric Parameters of Micro- and Nanomodified Epoxy Resin Using Electrophoresis

Modeling and simulation of shape memory nanocomposites

Contact Info

Product

Resources

About