Silica-reinforced dynamically vulcanized ethylene-propylene-diene monomer/polypropylene thermoplastic elastomers: Morphology, rheology, and dynamic mechanical properties

Attempts were made to prepare dynamically crosslinked ethylene-propylene-diene monomer/polypropylene (EPDM/PP, 60/40 w/w) blends loaded with various amounts of silica as a particulate reinforcing agent. The dispersion of silica between the two phases under mixing conditions, and also extent of interaction, as the two main factors that influence the blend morphology were studied by scanning electron microscopy. Increasing the silica concentration led to the formation of large-size EPDM aggregates shelled by a layer of PP. Dynamic mechanical thermal analysis performed on the dynamically cured silica-loaded blend samples showed reduction in damping behavior with increasing silica content. Higher rubbery-like characteristics under tensile load were exhibited by the silica-filled EPDM/PP-cured blends. However, increasing the silica level to 50 phr led to the enhancement of interface, evidenced by increases in the tensile modulus and extensibility of the blend compared with those of the unloaded sample. Addition of a silane coupling agent (Si69) into the mix improved the mechanical properties of the blend, attributed to the strengthening of interfacial adhesion between the PP matrix and silica-filled EPDM phase. (C) 2004 Wiley Periodicals, Inc.