An Investigation on Dispersion State of Graphene in Polypropylene/Graphite Nanocomposite with Extensional Flow Mixing.

Graphene nanoplatelets (GNP) have attracted considerable attention because of their excellent mechanical, thermal and electrical properties. Many researchers have tried to exfoliate GNP directly from graphite (Gr) in polymer by shear flow mixing process with twin-screw extruder, internal mixer and so on. By usual shear mixing, however, exfoliation of Gr into GNP is very difficult because of inefficiency process. Therefore, we focused on the extensional flow for exfoliating to GNP from Gr. In this study, the mixing effect of pure extensional flow for exfoliating into GNP was investigated by comparing with shear flow. Primary, PP/Gr masterbatch pellets were extruded by capillary rheometer equipped with orifice die (i.e. extensional flow) and capillary die (i.e. shear flow). Then, mixing effect was discussed by morphological and rheological analysis. As the results, extensional flow can exfoliate into few layer GNP with keeping larger sure face area by comparing shear flow and storage modulus G' was improved as the extensional stress is higher. [ABSTRACT FROM AUTHOR]