Dielectric relaxation and electrical conduction of polymers as a function of pressure and temperature

Saito, Shōgo; Sasabe, Hiroyuki; Nakajima, Tatsuji; Yada, Koji

doi:10.1002/pol.1968.160060708

Cited by 130 publications

(54 citation statements)

References 16 publications

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“…Previous workers have measured τ(P) for PVAc over a more limited frequency range at pressures below 300 MPa. 3,48,49 Over this smaller range, the relaxation times can be taken to be proportional to exp P, yielding an activation volume defined as ∆V ) 2.303RT(∂ log τ R /∂P) T . O'Reilly 3 reported activation volumes ranging from 130 to 200 mL/mol for temperatures from 390 to 340 K. These values are ca.…”

Section: Resultsmentioning

confidence: 99%

Temperature and Volume Effects on Local Segmental Relaxation in Poly(vinyl acetate)

2003

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Dielectric data on the local segmental relaxation of amorphous poly(vinyl acetate) (PVAc) are analyzed. At atmospheric pressure, the fragility (Tg-normalized temperature dependence) is invariant to molecular weight. Since the fragility is also independent of pressure, the combined temperature and pressure dependences of the relaxation times can be analyzed using the Avramov model of structural relaxation. This entropy model gives a satisfactory description of the data and yields an expression for the pressure dependence of the dynamic glass transition identical to the empirical Andersson equation. Although in principle the Avramov model parameters can be deduced from measurable thermodynamic properties of the glass-former, the results are at odds with the values obtained from fitting the relaxation times for PVAc. Using pressure-volume-temperature data, the respective contributions of thermal energy and volume to the local dynamics in PVAc were assessed. Specifically, we calculate the ratio of the isochoric to isobaric apparent activation energies. The obtained value, ≈0.6 at atmospheric pressure just above T g, indicates that temperature and volume both govern to a significant degree the relaxation times. This result is supported by a comparison of the relative magnitude of the isobaric and isochronal thermal expansion coefficients. These properties of PVAc are similar to those of other nonassociated polymers and glass-forming liquids and can be shown to be weakly correlated with the degree of super-Arrhenius behavior.

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Section: Resultsmentioning

confidence: 99%

Temperature and Volume Effects on Local Segmental Relaxation in Poly(vinyl acetate)

2003

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“…To a lesser extent dielectric techniques have been used to study the effect of pressure on the relaxations of phase materials [2][3][4][5][6][7][8][9]. By varying pressure, temperature and frequency, one can separate the activation energy and activation volume contributions to the activation enthalpy [4].…”

Section: Introductionmentioning

confidence: 99%

The dependence of dielectric response of an elastomer on hydrostatic pressure

Pae

Questad

1983

J. Polym. Sci. Polym. Phys. Ed.

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Dielectric methods have been employed to study the high‐pressure behavior of a polyurethane elastomer (Solithane 113) in the vicinity of its α transition. The α‐loss peak is shifted to higher temperatures and broadened somewhat with the application of hydrostatic pressure up to 6.4 kbars. The slope of Tα vs. P, or dTα/dP, obtained at low frequencies was found to be equal to dTg/dP obtained by a volumetric method. Moreover, it attained a nonzero limiting value at high pressures for each frequency tested (3—30,000 Hz) and the limiting value itself increased with increasing frequency from 10.5°C/kbar at 3 Hz to 18°C/kbar at 30,000 Hz. The activation enthalpy ΔH* was found to be nearly constant over the pressure range tested, but the activation volume ΔV* decreased with increasing pressure. The relation dTα/dP = T (ΔV*/ΔH*) was shown to hold for the elastomer.

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“…In the next step, drastic weight loss occurred at around 360°C. The weight loss at this temperature corresponds to degradation of the bisphenol A group of the epoxy polymer [29]. The MWCNT/epoxy composites showed improved thermal stability according to the MWCNT content in the epoxy resin compared to the neat epoxy composite.…”

Section: Tensile Characteristicsmentioning

confidence: 99%

Mechanical and thermal properties of MWCNT-reinforced epoxy nanocomposites by vacuum assisted resin transfer molding

Lee¹,

Cho²,

Lee

2014

Carbon letters

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Multi-walled carbon nanotube (MWCNT)/epoxy composites are prepared by a vacuum assisted resin transfer molding (VARTM) method. The mechanical properties, fracture surface morphologies, and thermal stabilities of these nanocomposites are evaluated for epoxy resins with various amounts of MWCNTs. Composites consisting of different amounts of MWCNTs displayed an increase of the work of adhesion between the MWCNTs and the matrix, which improved both the tensile and impact strengths of the composites. The tensile and impact strengths of the MWCNT/epoxy composite improved by 59 and 562% with 0.3 phr of MWCNTs, respectively, compared to the epoxy composite without MWCNTs. Thermal stability of the 0.3 phr MWCNT/epoxy composite increased compared to other epoxy composites with MWCNTs. The enhancement of the mechanical and thermal properties of the MWCNT/epoxy nanocomposites is attributed to improved dispersibility and strong interfacial interaction between the MWCNTs and the epoxy in the composites prepared by VARTM.

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Dielectric relaxation and electrical conduction of polymers as a function of pressure and temperature

Cited by 130 publications

References 16 publications

Temperature and Volume Effects on Local Segmental Relaxation in Poly(vinyl acetate)

Temperature and Volume Effects on Local Segmental Relaxation in Poly(vinyl acetate)

The dependence of dielectric response of an elastomer on hydrostatic pressure

Mechanical and thermal properties of MWCNT-reinforced epoxy nanocomposites by vacuum assisted resin transfer molding

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