Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Details of dynamic mechanical properties of dendritic poly(ether ketone)s in conjunction with their highly branched structure and degree of branching
Autore:
Ahn, DU; Kwak, SY;
Indirizzi:
Seoul Natl Univ, HOMRC, Kwanak Ku, Seoul 151742, South Korea Seoul Natl Univ Seoul South Korea 151742 k Ku, Seoul 151742, South Korea Seoul Natl Univ, Sch Mat Sci & Engn, Kwanak Ku, Seoul 151742, South Korea Seoul Natl Univ Seoul South Korea 151742 k Ku, Seoul 151742, South Korea
Titolo Testata:
MACROMOLECULAR MATERIALS AND ENGINEERING
fascicolo: 1, volume: 286, anno: 2001,
pagine: 17 - 25
SICI:
1438-7492(200101)286:1<17:DODMPO>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
MOLECULAR-WEIGHT DISTRIBUTION; COMPATIBLE POLYMER MIXTURES; HYPERBRANCHED POLYESTERS; TUBE MODEL; VISCOELASTICITY; DENDRIMERS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
29
Recensione:
Indirizzi per estratti:
Indirizzo: Kwak, SY Seoul Natl Univ, HOMRC, Kwanak Ku, San 56-1, Seoul 151742, South Korea Seoul Natl Univ San 56-1 Seoul South Korea 151742 2, South Korea
Citazione:
D.U. Ahn e S.Y. Kwak, "Details of dynamic mechanical properties of dendritic poly(ether ketone)s in conjunction with their highly branched structure and degree of branching", MACRO MAT E, 286(1), 2001, pp. 17-25

Abstract

To investigate the effects of unique hyper-branched structure on viscoelastic properties, three fluoro-terminated hyperbranched poly(ether ketone)s (HPEKs) with different degrees of branching (i.e., 0.49; HPEK49, 0.62; HPEK62, and 0.67; HPEK67) and the analogous Linear poly(ether ketone) (LPEK), whose chemical structure and molecular weights were similar to those of HPEK;s,were synthesized and characterized. From the analysis of plots of the dynamic loss modulus G(n)(omega) versus the storage modulus G'(omega) of the individud polymers, It was confirmed that the amount of entanglements between polymer -molecules decreased as the degree of branching increased, exhibiting a nearly Newtonian behavior particullar for the HPEK with degree of branching of 0.67 (HPEK67)- Furthermore, the G "(omega) versus G'(omega) plots indicated the narrowing of molecular weight distribution and/or shortening of branches with increasing degree of branching, being shown to shift thecurves from lower to higher G "(omega) values. From the master curves of HPEKs obtained by the time-temperature superposition principle, it was investigated that the rubbery plateau region and the crossover of G'(w) and G " (w) started to disappear at a hitical value (>0.62-0.67) of the degree of branching, indicating a nearly Newtonian or Little entanglement now. Moreover, it could be predicted from the tendency of the shift factor a(T), obtained from the master curve, that the molecular mobility and temperature dependence of individual HPEKs increased as the degree of branching increased. The shift factors of HPEKs fit with the Williams-Landel-Ferry (WLF) equationresulted in a more temperature dependent non-Arrhenius behavior than that of LPEK as the degree of branching increased, implying a fragile amorphous polymer. From the nonlinear curve fittings of shift factors by the Vogel-Tamman-Fulcher (VTF) equation, it was further quantified that the HPEKs were more fragile than the LPEK and the fragility increased with increasing degree of branching, which indicated that the branching structure induced the fragility in the materials.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 23/09/20 alle ore 06:05:00