The temperature dependence of the local free volume in polyethylene and polytetrafluoroethylene: A positron lifetime study

Dlubek, G.; Saarinen, K.; Fretwell, H. M.

doi:10.1002/(sici)1099-0488(19980715)36:9<1513::aid-polb9>3.0.co;2-k

Cited by 134 publications

(156 citation statements)

References 17 publications

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“…The lifetime spectra in PE and PTFE show four components, the two long--lived ones are attributed to o-Ps annihilation in free volumes in the crystalline (τ3 = 1.0-1.2 ns) and amorphous phases ( τ 4 = 1.5-2.7 ns in PE and 2.5-4.3 ns in PTFE) [1]. From the o-Ps lifetimes the hole volumes v are estimated using the well-known formula developed by Tao, Eldrup, and Jean and collaborators [2].…”

Section: Resultsmentioning

confidence: 99%

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Relations Between Hole Volume and Macroscopic Volume in Various Polymers

et al. 1999

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Different definitions of the free volumes are discussed and related to the total specific volume and to the local free (hole) volume. Positron lifetime measurements are reported for polyethylene, polytetrafluoroethylene, and CR39-copolymers. Two long-lived components appear in polyethylene and polytetrafluoroethylene, which were attributed to o-Ps annihilations in crystalline regions and in holes of the amorphous phase. From a relation between the coefficients of the thermal expansion of macroscopic and hole volume, the fractional hole volume h and from this the number of holes, N, is estimated. Values of Tg = 195 K, hg = 4.5% (polyethylene) and 5.7% (polytetrafluoroethylene) and Ng = 0.73 nm -3 (polyethylene) and 0.36 nm -3 (polytetrafluoroethylene) were obtained. In semicrystalline polymers these values agree with estimates obtained from the densities of the crystalline and amorphous phases. The effect of cross-linking on the free-volume properties of CR39-copolymer networks was studied. The comparison of the hole volume with the specific volume allowed us to estimate the number density of holes to = 1 nm -3 .

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Section: Resultsmentioning

confidence: 99%

“…We may now compare these values with those obtained via Eq. (1). With p a = 0.85 g/cm3 , pc = 1 g/cm 3 (PE) and Pa = 2.00 g/cm3 , pc = 2.35 g/cm3 we obtain h(300 K) = 15.0% (PE) and 14.9% (PTFE).…”

Section: (T)mentioning

confidence: 98%

Relations Between Hole Volume and Macroscopic Volume in Various Polymers

et al. 1999

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“…These interfacial and void structural motifs are thought to play an important role in dielectric breakdown. Note however that although nanometre sized holes (average radius, r h = 0.343 nm) are present, 12 amounting to 13.2% of the total volume at 300 K in low density polyethylene (LDPE) from positron lifetime studies, 13 the literature usually considers μm sized voids as initiators of mechanical and electrical breakdown.…”

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confidence: 99%

Single electron states in polyethylene

Wang

MacKernan

Cubero

et al. 2014

The Journal of Chemical Physics

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We report computer simulations of an excess electron in various structural motifs of polyethylene at room temperature, including lamellar and interfacial regions between amorphous and lamellae, as well as nanometre-sized voids. Electronic properties such as density of states, mobility edges, and mobilities are computed on the different phases using a block Lanczos algorithm. Our results suggest that the electronic density of states for a heterogeneous material can be approximated by summing the single phase density of states weighted by their corresponding volume fractions. Additionally, a quantitative connection between the localized states of the excess electron and the local atomic structure is presented.The US National Science Foundation under grant CHE-0911635 and from his Stokes Professorship in Nano Biophysics from Science Foundation Ireland thanks the Irish Centre for High End Computing (ICHEC) for computer resources and Science Foundation Ireland for support from grant 08-IN.1-I1869

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“…It is possible to evaluate the fractional free volume at Tg without resorting to "hole number" 42) . The total thermal expansion coefficient can be written as = f f o (1 f ), where f and o are for the free and occupied volumes, respectively, and f is again supposed to be equal to the expansion coefficient of Ps hole, Ps.…”

Section: Free Volume Fractionmentioning

confidence: 99%

Vacancy Spectroscopy Using Positronium

Ito¹,

Mohamed

Shantarovich

et al. 2009

membrane

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Positron annihilation technique as a probe of subatomic vacancies is described for non-positron polymer scientists.Although positronium (Ps) is an unparalleled unique probe of inter-molecular vacancies in insulating materials, with both its intensity and mean lifetime carrying information about the free volume, the processes that lead to these physical quantities are not simple. The state-of-the-art understandings of how Ps is created and how its mean lifetime is determined in vacancies are described, and examples of the unique feature as well as the problems and precautions are illustrated.

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The temperature dependence of the local free volume in polyethylene and polytetrafluoroethylene: A positron lifetime study

Cited by 134 publications

References 17 publications

Relations Between Hole Volume and Macroscopic Volume in Various Polymers

Relations Between Hole Volume and Macroscopic Volume in Various Polymers

Single electron states in polyethylene

Vacancy Spectroscopy Using Positronium

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