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Titolo:
Relations between hole volume and macroscopic volume in various polymers
Autore:
Dlubek, G; Alam, MA; Saarinen, K; Stejny, J; Fretwell, HM;
Indirizzi:
ITAanyst Innovat Technologien GmbH, Aussenstelle Halle, D-06124 Halle, Germ ITA Inst Innovat Technologien GmbH Halle Germany D-06124 124 Halle, Germ Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England Univ Bristol Bristol Avon England BS8 1TL Bristol BS8 1TL, Avon, England Helsinki Univ Technol, Phys Lab, FIN-02150 Espoo, Finland Helsinki Univ Technol Espoo Finland FIN-02150 , FIN-02150 Espoo, Finland
Titolo Testata:
ACTA PHYSICA POLONICA A
fascicolo: 4, volume: 95, anno: 1999,
pagine: 521 - 526
SICI:
0587-4246(199904)95:4<521:RBHVAM>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
POSITRON LIFETIME; POLYTETRAFLUOROETHYLENE; POLYETHYLENE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
7
Recensione:
Indirizzi per estratti:
Indirizzo: Dlubek, G ITA Inst Innovat Technologien GmbH, Aussenstelle Halle, Edvard Grieg Weg 8, ITA Inst Innovat Technologien GmbH Edvard Grieg Weg 8 Halle Germany D-06124
Citazione:
G. Dlubek et al., "Relations between hole volume and macroscopic volume in various polymers", ACT PHY P A, 95(4), 1999, pp. 521-526

Abstract

Different definitions of the free volumes are discussed and related to thetotal specific volume and to the local free (hole) volume. Positron lifetime measurements are reported for polyethylene, polytetrafluoroethylene, andCR39-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 T-g = 195 K, h(g) = 4.5% (polyethylene) and 5.7% (polytetrafluoroethylene) and Ng = 0.73 nm(-3) (polyethylene) and 0.36 nm(-3) (poly tetrafluoroethylene) 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 withthe specific volume allowed us to estimate the number density of holes to approximate to 1 nm(-3).

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Documento generato il 29/05/20 alle ore 17:04:52