Viscosity–molecular weight–temperature–shear rate relationships of polymer melts: A literature review

Abstract." A procedure for evaluating rheological characteristics, such as the master curves log r//r/0 vs. log pv/0 and flow curves, using the melt flow index is described for branched and linear polymers. Experimental data on the melt flow index and branching degree are needed for this purpose, as well as some polymer constants, i.e. coefficients of the v/0 vs. MFI relation and coefficients of fluidity dependence on molecular characteristics. An example is given for bisphenol A polycarbonate.

Section: Results and Diseussionsupporting

confidence: 51%

“…If the temperature and, for polymer solutions, the concentration are also taken into account, cf. [14], it can be suggested that the position of the t/vs. ?…”

Section: Results and Diseussionmentioning

confidence: 97%

Application of melt flow index for rheological characterization of branched and linear polymers

Dobkowski

1986

“…However, it was suggested that the change from eq. (12) to (13) does not involve a discontinuity, so that an intermediate behaviour should be expected for molecular weights near M c [15]. Since the Mw values of the polypropylene samples studied here are far above Mc (M~ -~ 7000 for polypropylene [16]) it is expected that viscosity values fit well into eq.…”

Section: Influence Of M~ and M W D O N Qo And %mentioning

confidence: 81%

An investigation of the viscoelastic properties of molten polypropylene

Ottani¹,

Pezzin

Castellari

1988

Two series of polypropylene samples of different molecular weight, the first obtained directly from polymerization reactions and the second from controlled thermal degradation, were studied by dynamic testing in the melt state. Several viscoelastic parameters were determined, and correlated with weight-average molecular weight Mw. It is found that the Mw-dependence of the two series is rather different.

“…Une revue tr6s compl6te de ces sujets a 6t6 r6alis6e par Kumar [10]. Ces th6ories bas6es sur des repr6sentations r6duites de la viscosit6 ont montr6 que la largeur du plateau Newtonien augmentait quand la polydispersit6 du mat6riau diminuait.…”

Section: Discussion Et Conclusionunclassified

Influence de la polydispersit� sur le comportement rh�ologique � l'�tat fondu du polypropyl�ne

Verney

Michel²

1985

Rdsum~: L'etude des proprietes rheologiques dynamiques g l'etat fondu du polypropylene montre l'influence des parametres moleculaires sur son comportement viscoelastique. Nous avons tent6 de relier la polydispersite du materiau fi certains parametres rheologiques. Une relation entre la valeur de la tangente de perte pour la frequence qui correspond au temps de relaxation moyen et la largeur de la distribution des masses moleculaires a pu etre 6tablie.Abstract: Dynamic melt rheology studies of polypropylene show that the molecular parameters influence its viscoelastic behaviour. We have attempted to correlate polydispersity values of the samples with some rheological parameters. A relation between the value of the loss tangent at the frequency corresponding to the average relaxation time and the molecular weight distribution has been established.