Micro-scale morphologies of EPDM/EOC/PP ternary blends: Relating experiments to predictive theories of dispersion in melt mixing

This present work deals primarily with uncertainty and measurement problems in determining the phase morphology and the polymer compatibility in some blend systems. Ternary blends in the form of dynamically vulcanized EPDM/EOC in PP matrix were investigated across EPDM/EOC blend ratios. Both rheological study and SEM micrographs attribute the compatibilizing effects to the EOC, which acts as a wetting agent at the EPDM/PP interfaces between phases. This reduces the size of dispersed elastomer phases and prevents the coalescence of dispersed domains, in a dose-dependent manner with EOC content. The estimated interfacial tension, work of adhesion, relative interfacial energy and viscosity ratio of the blend components indicate that potentially the EOC phase has with the PP phase greater compatibility and stronger interactions than it has with the EPDM. Morphologically the EPDM/EOC/PP ternary blend has core–shell structures, with EPDM-cores encapsulated by EOC-shells, and such core–shell particles dispersed in the PP matrix. Moreover, the dispersed elastomer phases with core–shell structure are found to dominate when the volume fraction of EOC in the blend is sufficient. Keywords: Polymer blends, Dynamic vulcanization, Phase morphology, Interfacial properties, Melt viscosity, SEM observation