Rheological properties of incompatible blends of two elastomers

Abstract

Mold flows and melt viscosities of an incompatible bi‐component EPDM and “Viton” fluoroelastormer system were examined. A marked reduction in the melt viscosities of either component was observed when a small amount of the other component was present. It was speculated that the phenomenon was a result of a slippage between the polymer and the coated capillary surface due to the presence of a minor amount of the incompatible polymer. Evidence is given to indicate that this effect cannot be accounted for using the “melt structural heterogeneity” mechanism proposed for a different system by Andtrianova.

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“…11 with or without the Bagley end-correction does not make sense for dispersed immiscible polymer blends. Nevertheless, some investigators [2][3][4][5][6][7][8] did just that without realizing the fact that Eq. 4 is only valid for homogeneous fluids and that the morphology (the state of dispersion) of an immiscible polymer blend keeps changing, undergoing very large drop deformations and possibly drop breakup (see Figs.…”

“…Thus, I conclude that the viscosity data of immiscible polymer blends reported in the literature [2][3][4][5][6][7][8], which were determined from the use of a plunger-type capillary viscometer with the aid of Eq. 4 with or without the Bagley end-correction n B , are subject to serious criticism.…”

“…6). In the past, several research groups [2][3][4][5][6][7][8] mistakenly used a plunger-type viscometer (e.g., Instron viscometer) to erroneously calculate the shear viscosities of immiscible polymer melts using Eq. 4, with or without n B .…”

“…. N), the volumetric flow rate Q (via _ c app ¼ 4Q=pD 3 with D being the tube diameter), the viscosity of the suspending medium g m , and the viscosity ratio g d /g m with g d being the viscosity of the drop phase, and interfacial tension c:…”

“…The purpose of this review article is to clear the confusion in the literature on the following two issues. First, I will point out that measurement of the total pressure drop across the entire length of a capillary die, while using a plunger-type viscometer, to determine the bulk viscosity of immiscible polymer blends forming two phases, which was reported by some research groups [2][3][4][5][6][7][8], is not justified. Second, I will point out that it is of no rheological significance to determine the composition dependence of the bulk viscosity of immiscible polymer blends using such empirical expressions as inverse additivity or logarithmic additivity relationships, which were used by some investigators [5,6,[9][10][11][12][13].…”