The relationship between rheology, morphology and physical properties in heterogeneous blends

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Abstract
The morphology of heterogeneous blends of polybutadiene (PBD) and EPDM was selectively varied by a change of either the rheology of the blend components during mixing or of the blend composition. Under a given set of mixing conditions, the blend system approaches a “steady state morphology”, which was found to be relatively independent of sample history. However, during subsequent compression molding, the morphology of the sample may be altered substantially with phase inversion occurring in some cases. A mechanism is proposed for the observed rheology‐morphology behavior.The strain moduli of the vulcanizates prepared by irradiation of the elastomer blends were similar to those predicted using the parallel Takayanagi models. A positive synergism with respect to energy to break and stress at break was noted particularly in cases where the blend components showed a significantly different mechanical response. The sensitivity of the stress‐strain response of these blends to changes in morphology was less than anticipated. This is attributed to restrictions imposed on the movement of the softer phase by the hard phase component of the blend.

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