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Titolo:
Formation, structure, thermal and dynamic mechanical behaviour of ordered polyurethane networks based on mesogenic diol
Autore:
Valentova, H; Sedlakova, Z; Nedbal, J; Ilavsky, M;
Indirizzi:
Charles Univ, Fac Math & Phys, CR-18000 Prague 8, Czech Republic Charles Univ Prague Czech Republic 8 , CR-18000 Prague 8, Czech Republic Acad Sci Czech Republ, Inst Macromol Chem, CR-16206 Prague, Czech RepublicAcad Sci Czech Republ Prague Czech Republic CR-16206 gue, Czech Republic
Titolo Testata:
EUROPEAN POLYMER JOURNAL
fascicolo: 8, volume: 37, anno: 2001,
pagine: 1511 - 1517
SICI:
0014-3057(200108)37:8<1511:FSTADM>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
LIQUID-CRYSTALLINE POLYURETHANES; POLYMER NETWORKS; GEL POINT; ELASTOMERS; CHAIN;
Keywords:
LC networks; dynamic modulus; sol-gel transition; gel point; power-law behaviour; frequency-temperature superposition;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
17
Recensione:
Indirizzi per estratti:
Indirizzo: Ilavsky, M Acad Sci Czech Republ, Inst Macromol Chem, CR-16206 Prague 6, Czech Republic Acad Sci Czech Republ Prague Czech Republic 6 Czech Republic
Citazione:
H. Valentova et al., "Formation, structure, thermal and dynamic mechanical behaviour of ordered polyurethane networks based on mesogenic diol", EUR POLYM J, 37(8), 2001, pp. 1511-1517

Abstract

Dynamic mechanical and thermal behaviour of ordered linear and crosslinkedpolyurethane systems based on a mesogenic diol, 4,4'-bis(11-hydroxyundecyloxy)biphenyl (D), 2(4)-methyl-1,3-phenylene diisocyanate (DI) and poly(oxypropylene)triol (T) was investigated during network formation and in fully cured samples. The networks were prepared at various stoichiometric initial molar ratios of the reactive groups, [OH](T)/[NCO](DI)/[OH](D) ranging from1/1/0 to 1/12/11. for comparison, linear sample with the ratio 0/1/1 was also investigated. From our measurements it followed: (a) The power-law parameters, which are characteristic of the critical structure at the gel point(the gel strength S and relaxation exponent n), are dependent on the initial ratio of the reactive groups. With increasing content of mesogenic diol in network chain (increasing length of elastically active network chain (EANC)) both, the gel strength S and relaxation exponent n decrease. (b) Introduction of chemical junctions reduces flexibility of the EANCs in fully cured networks and inhibits conformational rearrangements required for ordering. Increasing the content of mesogenic diol in EANCs increases the concentration of permanent physical interactions (trapped entanglements) in the systems and the intensity of the slow relaxation process in the rubbery region. (C) 2001 Elsevier Science Ltd. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 14/07/20 alle ore 05:51:22