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Rheology of polymer blends: Simultaneous slippage and entrance pressure loss in the ethylene‐propylene‐diene (EPDM)/viton system
Author(s) -
Kanu R. C.,
Shaw M. T.
Publication year - 1982
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760220809
Subject(s) - materials science , ethylene propylene rubber , slippage , rheology , composite material , polymer science , polymer , ethylene , diene , copolymer , polymer chemistry , natural rubber , organic chemistry , catalysis , chemistry
Because the exact nature of the mechanism governing the marked viscosity reduction in the highly incompatible EPDM/“Viton” fluoroelastomer system is not fully understood, a study was undertaken to shed more light on the phenomenon. Interracial. Slippage in the blend has been suggested as the mechanism by which a substantial reduction in the melt viscosities of either component takes place upon addition of a small amount of the other, In the present investigation, a Mooney slip analysis demonstrated wall slippage in the EPDM/Viton system over the shear stress range of 40 kPa to 160 kPa. The capillary surface was examined for evidence of coating by the minor component of the blend (Viton), and 9‐fold enrichment was found by elemental analysis. However, on no occasion was pure Viton found. In other experiments, the dynamic linear viscoelastic properties and the transient squeezing flow response of the blend were found to be no different from those of the neat elastomer. In addition, the slip velocity in a capillary (and consequently, the viscosity‐lowering effect) was reduced by a factor of 2 to 3 in capillaries with a 90° included entrance angle. It is postulated that the reduction in the flow resistance for the blend is unique to the sharp‐entry capillary geometry and results from removal of Viton from the melt in the recirculating flow at the entrance. This material then feeds along the capillary wall, disrupting the already tenuous adhesion of the elastomer to the metal surface.