The effect of nanoplatelets on the rheological behavior of epoxy monomers with variations in nanoplatelet exfoliation level and aspect ratio was investigated. The results show that the presence of exfoliated nanoplatelets in epoxy can significantly influence viscosity and lead to shear‐thinning phenomena, especially when the aspect ratio of the nanoplatelets is high. By employing the Krieger‐Dougherty model, the effectiveness of nanoplatelets in altering epoxy rheological behavior was quantitatively described and compared with experimental findings. Possible physical reasons for the observed rheological behaviors are discussed. The implication of the present study for polymer nanocomposites processing is also addressed.magnified image

ABSTRACT:The impact fracture mechanisms of polypropylene (PP), containing 9.2 vol % of calcium carbonate (CaCO 3 ) nanoparticles, were investigated using optical microscopy and transmission electron microscopy. The incorporation of CaCO 3 nanoparticles reduces the size of spherulites and induces the formation of ␤-phase crystallites, which leads to a more ductile PP matrix. Double-notch four-point bending (DN-4PB) Charpy impact specimens and notched Izod impact specimens were utilized to study the fracture mechanism(s) responsible for the observed toughening effect. A detailed investigation reveals that the CaCO 3 nanoparticles act as stress concentrators to initiate massive crazes, followed by shear banding in PP matrix. These toughening mechanisms are responsible for the observed, improved impact strength. A comparison of the fracture mechanisms observed between DN-4PB Charpy and Izod impact tests is also made to show the effectiveness of DN-4PB for investigation of impact fracture mechanisms of polymeric systems.