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Titolo:
Characterization of the molecular structure of two highly isotactic polypropylenes
Autore:
Viville, P; Daoust, D; Jonas, AM; Nysten, B; Legras, R; Dupire, M; Michel, J; Debras, G;
Indirizzi:
Univ Catholique Louvain, Fac Sci Appliquees, Unite Phys & Chim Hauts Polymeres, B-1348 Louvain, Belgium Univ Catholique Louvain Louvain Belgium B-1348 , B-1348 Louvain, Belgium FINA RES SA, B-7181 Seneffe, Belgium FINA RES SA Seneffe Belgium B-7181FINA RES SA, B-7181 Seneffe, Belgium
Titolo Testata:
POLYMER
fascicolo: 5, volume: 42, anno: 2001,
pagine: 1953 - 1967
SICI:
0032-3861(200103)42:5<1953:COTMSO>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
ZIEGLER-NATTA CATALYSTS; RISING ELUTION FRACTIONATION; ETHYLENE-PROPYLENE COPOLYMERS; MICROSTRUCTURAL ANALYSIS; WEIGHT; DISTRIBUTIONS; POLYOLEFINS; TACTICITY; KINETICS;
Keywords:
temperature rising elution fractionation; polypropylene; molecular structure;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
23
Recensione:
Indirizzi per estratti:
Indirizzo: Daoust, D Univ Catholique Louvain, Fac Sci Appliquees, Unite Phys & Chim Hauts Polymeres, Batiment Boltzmann,Pl Croix Sud 1, B-1348 Louvain, Belgium Univ Catholique Louvain Batiment Boltzmann,Pl Croix Sud 1 Louvain Belgium B-1348
Citazione:
P. Viville et al., "Characterization of the molecular structure of two highly isotactic polypropylenes", POLYMER, 42(5), 2001, pp. 1953-1967

Abstract

Two polypropylenes, PP1 and PP2, produced with different heterogeneous Ziegler-Natta catalytic systems were studied in this work. Preliminary characterization of the non-fractionated materials showed that a low difference intheir average tacticity (PP2 > PP1) leads to an important modification of their rigidity properties. In order to establish correlation between the molecular structure parameters and the rigidity properties of these polymers,fractionation of the materials according to crystallizability was performed by means of temperature rising elution fractionation (TREF). Analysis of the fractions of both PP1 and PP2 was carried out by means of C-13 NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The results first showed that TREF does not strictly fractionate PP according to tacticity, but according to the longest crystallizable sequence in a chain. C-13 NMR, SEC and DSC analysis of the fractions demonstrated that the inter-chain tacticity distributions of the polypropylenes is affected by the change of the polymerization conditions, which, in turn, modifies the rigidity properties of the materials. Someresults also seem to indicate that the intrachain tacticity distributions are different for the two PP. An AFM study of the elastic modulus was carried out for the first time on the TREE fractions. It showed that the rigidity or the fractions strongly increases as the TREF elution temperature increases in accordance with a concomitant increase of isotacticity and the crytallinity of the fractions. PP2 TREE fractions were, moreover, found to exhibit a higher elastic modulus than PP1 TREF fractions at all elution temperatures. This study allowed us to further identify the TREF fractions that were responsible for differences in rigidity. To summarize, it is shown how the experimentally observed increase of the average rigidity of one of thesetwo polypropylenes can be rationalized via information collected from a TREF fractionation. (C) 2000 Published by Elsevier Science Ltd.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/07/20 alle ore 18:19:40