Characterization of Zinc Stearate Plasticized Sulfonated EPDM by Real-Time SAXS and WAXS.

摘要

Lightly sulfonated poly(ethylene-propylene-ethylidene norborene), SEPDM, ionomers are potential thermoplastic elastomers. At ambient temperatures, interchain associations of the sulfonate dipoles give the material properties characteristic of a crosslinked rubber, while at elevated temperatures and under stress, these labile 'crosslinks' weaken sufficiently to allow for melt flow of the ionomer. Even at very low sulfonation levels, such as 30 meq sulfonate groups per 100g of rubber (phr), the melt viscosity of SEPDM is too high to be practical in most common polymer processing operations. Significant reductions in the melt viscosity may be achieved, however, by the addition of polar additives that preferentially interact with the ionic associations. One particular plasticizer, zinc stearate (ZnSt), not only improves the melt flow of SEPDM, but also improves the room-temperature mechanical properties. In this paper, we describe the use of real time small angle and wide angle x-ray scattering (SAXS and WAXS, respectively) to characterize the temperature-dependent microstructure of a ZnSt-plasticized SEPDM. Differential scanning calorimetry (DSC) measurements were used to compliment the x-ray data. Reprints. (aw)