Phase morphology and mechanical properties of ethylene-propylene-diene-monomer/fluoroelastomer blends

Rubber blends based on ethylene-propylene-diene-monomer (EPDM) rubber and fluoroelastomer (FKM) having various blend ratios were prepared. The phase morphology, cure characteristics, hardness, tensile and dynamic vis-coelastic properties of the blends were investigated. The cure rate of the blends increased, while the crosslink-density decreased as the FKM content increased. The hardness, tensile strength and elongation at break, and storage modulus (E) increased with increasing FKM loading. A typical incompatible blend behavior was found by observing two distinct tanS peaks corresponding to EPDM and FKM. Based on the morphology investigation by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) analyses, a typical 'sea-island' phase morphology was observed for the EPDM/FKM blends. As the FKM loading was increased to 50 phr, the EPDM was found to remain as the continuous phase. At the 80 phr of FKM, a co-continuous phase was observed and the phase inversion was observed at 90 phr of FKM.