Design of thermal conductive polymer composites with precisely controlling graphene nanoplatelets at the interface of polypropylene and high melt strength polypropylene via elongation flow

Abstract

AbstractThe migration and selective localization of graphene nanoplatelets (GNPs) in a polypropylene/high melt strength polypropylene (PP/HMSPP) blend under elongational and shear forces are studied. The effects of elongational flow upon the elongational rheology, X‐ray diffraction patterns, thermal properties, and mechanical properties are investigated. The results show that the elongational viscosity and melt strength of HMSPP are higher than those of PP under elongational flow, whereby HMSPP shows elongational strain hardening behavior, and the migrating of GNPs from the PP to the HMSPP phase is hindered. As a result, the GNPs are constrained to remain at the interface between the two phases. In addition, the elongational force can exfoliate GNPs more effectively, and the orientation of GNPs along the phase interface will reduce the migration rate of GNPs at the interface, while precisely controlling the location of the GNPs at the phase interface. Thus, more thermal conductivity pathways are constructed and, hence, the thermal conductivity of the PP/HMSPP/GNPs composite prepared under elongational flow is higher than that prepared under shear flow. The present work provides a new method for the preparation of highly thermally conductive polymer composites.