Ions containing EPDM

In order to enable melt processing of ion containing polymers, such as S-EPDM, it is necessary to introduce a mechanism that weakens the ionic interactions. This can be achieved by the addition of a polar ingredient that would plasticize" ionic domains at elevated temperatures only. A variety of such ionic-plasticizers were described by Makowski and Lundberg (10). A particularly attractive combination was found to be zinc stearate with a zinc salt of S-EPDM. It was shown that for such a combination melt... 

Tables I and II dealt only with monovalent quaternary counterions Table III compares some divalent quaternary counterions with monovalent counterions. In Table III, the free acid sulfonated EPDM used to prepare Sample 15 was from a different preparation than that used for the other samples of this table. However, samples having the same counterion that were prepared from these two different batches of free acid had roughly comparable properties, so semiquantitative comparisons are justified. The first point to note in Table III is that one of the divalent counterion samples, 16, containing the tetradecamethylene bistriethylphosphonium ion, has greater tensile properties and a lower melt-flow rate than any of the three monovalent samples. The other divalent sample, 15, containing the ethylene bistrioctylphosphonium ion, has much lower tensile properties as well as a much higher melt-flow rate than any of the monovalent samples. That is, one of the samples containing a divalent counterion (Sample 16) is much tougher than any of the monovalent samples in...

This finding is consistent either with a non-spherical structure of the clusters, or with a sphere which deforms when the sample is stretched. It is clear that much further work remains to be done on the elucidation of the shape of the clusters, as well as the geometrical arrangements of the components, i.e. the ions and the polymer chains. This is true not only of the "classical" ionomers, i.e. those based on ethylene, styrene, or the rubbers, but also of the newly developed materials which contain ionic domain plasticizers, consisting of materials such as EPDM ionomers plasticized with zinc stearate. The field should remain a most challenging one in the foreseeable future. 

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