Concurrent effect of shear flow and CNT presence on crystallization behavior and electrical properties of polypropylene based nanocomposites: A comprehensive structure-property investigation

The loading of nanoparticle in the polymer matrix affects their response to shear flows applied during the fabrication process. With this in mind, in the present study, the concurrent effect of carbon nanotube (CNT) presence and shear application on the rheological and electrical properties as well as on the crystallization behavior of polypropylene (PP) based nanocomposites has been investigated. The results of rheological analyses showed that the solid-like behavior increases in proportion to the CNT content, and a remarkable increase in the solid-like behavior is obtained at a CNT content of 2 wt%. The isothermal crystallization results corroborated that crystallization temperature increases proportionally with the CNT content, however does not change with shearing. The non-isothermal crystallization findings confirmed that crystallization kinetics promotes with increasing CNT content, and this effect becomes more pronounced with shearing. The results of thermal analysis confirmed that the melting temperature decreases slightly, and the crystallinity remains almost unchanged with increasing CNT content up to 2%. However, when the CNT content rose up to 4%, the crystallinity decreased significantly due to confined crystallization. When this nanocomposite was subjected to shearing, the crystallinity increased. The results of electrical conductivity measurement revealed that the conductivity increases with increasing CNT content, while it decreases with shearing and the vulnerability of nanocomposites to shearing decreases with increasing CNT content.