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Titolo:
A BRILLOUIN-SCATTERING INVESTIGATION OF RELAXATION VERSUS CROSS-LINK DENSITY IN GLASS-FORMING AND GEL-FORMING POLYMERS
Autore:
LEVELUT C; SCHEYER Y; BOISSIER M; PELOUS J; DURAND D; EMERY JR;
Indirizzi:
UNIV MONTPELLIER 2,LAB SCI MAT VITREUX,URA CNRS 1119,CASE 069 F-34095MONTPELLIER FRANCE UNIV MAINE,UA CNRS 509,LAB CHIM & PHYSICOCHIM POLYMERES F-72017 LE MANS FRANCE UNIV MAINE,UA CNRS 807,LAB PHYS ETAT CONDENSE F-72017 LE MANS FRANCE
Titolo Testata:
Journal of physics. Condensed matter
fascicolo: 8, volume: 8, anno: 1996,
pagine: 941 - 957
SICI:
0953-8984(1996)8:8<941:ABIORV>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
DYNAMIC LIGHT-SCATTERING; POLY(METHYL METHACRYLATE); HYPERSONIC RELAXATION; ALPHA-RELAXATION; WILLIAMS-WATTS; SYSTEMS; TRANSITION; GELATION; LIQUIDS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
48
Recensione:
Indirizzi per estratti:
Citazione:
C. Levelut et al., "A BRILLOUIN-SCATTERING INVESTIGATION OF RELAXATION VERSUS CROSS-LINK DENSITY IN GLASS-FORMING AND GEL-FORMING POLYMERS", Journal of physics. Condensed matter, 8(8), 1996, pp. 941-957

Abstract

A Brillouin scattering study of the relaxational processes above the calorimetric glass transition temperature T-g (in the 1.2-1.6 T-g temperature range) on polyurethane gels is presented. The specificity of this work is to investigate several samples corresponding to various crosslink densities. The relaxational process observed by Brillouin scattering is compared to low-frequency measurements of the relaxational processes by other techniques: in contrast to low-frequency determinations, the Brillouin scattering relaxation time exhibits an Arrhenius behaviour for all the samples; however, the characteristic parameter of the time distribution width is the same for the two processes. The low-frequency relaxation and the high-frequency Brillouin scattering relaxation seem to merge for temperatures higher than 1.6 T-g and these data are discussed on the basis of different models for the glass transition. The influence of the crosslink density yields an increase of themean relaxation time with increasing connectivity and small variations of the apparent activation energy. In contrast, the distribution time width is not composition dependent. Nevertheless, the most striking results are that a rescaling to T-g fully accounts for the variations of the mean relaxation time with the crosslink density and a correspondence between the crosslink density and the inverse of the temperatureis suggested.

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Documento generato il 02/12/20 alle ore 18:35:58