Stiffness-toughness balance in PP/EPDM/SiO <sub>2</sub> ternary blend-nanocomposites: The role of microstructural evolution
Sina Hajibabazadeh, Mir Karim Razavi Aghjeh, Majid Mehrabi Mazidi
Abstract
The effect of microstructural evolution with hydrophilic-nanosilica (SiO 2 ) concentration, ranging from 0 to 5 wt%, on mechanical properties and deformation micromechanisms of PP/EPDM/SiO 2 (80/20/x) ternary blend-nanocomposites was investigated. Morphological observations revealed that, SiO 2 nanoparticles tend to localize either around the dispersed EPDM particles or at the PP/EPDM interface, promoting the formation of three dimentional network-like EPDM/SiO 2 composite structures dispersed in the PP matrix, especially at higher SiO 2 loadings. This type of dispersion state was further confirmed by the rheological analysis. Synergistic toughening effect of soft EPDM particles and rigid SiO 2 particles under Izod impact test was observed in these ternary systems, so that the materials with a better balance of stiffness/toughness were achieved. The results demonstrated that the extent of impact toughness increase is higher, where a large amount of the SiO 2 nanoparticles surrounded the EPDM dispersed particles distributed in the PP matrix. This significant increase was attributed to the change in the size of stress concentration region and evolution of stress distribution throughout the material. The failure mechanisms were studied, and the underlying toughening micromechanisms were proposed.