Development of Dispersion during Compounding and Extrusion of Polypropylene/Graphite Nanoplates Composites

Carbon-based nanoparticles have unique electrical, thermal, barrier and mechanical properties. When incorporated into polymer matrices, the resulting nanocomposites are potentially suitable for a wide scope of advanced applications. In practice, the properties of the nanocomposites are strongly determined by the level of dispersion achieved and by the degree of polymer/particle interfacial bonding. Production and processing of nanocomposites are often carried out in successive thermo-mechanical cycles. These may change the state of nanoparticle dispersion. This work analyzes the evolution of the dispersion of graphite nanoplates (GnP) in a polypropylene matrix during compounding in a co-rotating twin screw extruder and subsequent processing in a single screw extruder, aiming at a better understanding of the kinetics and stability of dispersion. Dispersion was evaluated along the compounding and processing stages and correlated with the composite electrical conductivity, an important engineering property. Two commercial GnP were used as received and chemically modified to graft PP-g-MA (fGnP-PP). Compositions with 2 or 10 wt.% of GnP and fGnP-PP were studied.