Influence of chain mobility on rheological, dielectric and electromagnetic interference shielding properties of poly methyl-methacrylate composites filled with graphene and carbon nanotube

Rheological, dielectric and electromagnetic interference shielding (EMI) properties of multi-walled carbon nanotube (MWCNT) and graphene nano-pellets (GNP) poly(methyl methacrylate) (PMMA) composites were compared. The GNP readily formed a polymer-mediated filler network compared to MWCNT, as evidenced by rheological tests. Immobilization of the interphase region was higher under the influence of the GNP in comparison with the MWCNT. However, the MWCNT-filled samples showed superior dielectric properties in respect to the GNP-filled samples. Particle shape and polymer chain dynamics in the interphase affected the dielectric properties. It was hypothesized that intensive immobilization, resulted from the GNP network, reduced free volume for segmental chain movements and dipole orientation along the applied electric field; which caused a decrease in dielectric permittivity. The MWCNT-filled samples were more efficient in electromagnetic wave absorption and reflection in comparison with the GNP-added samples which is ascribed to the one-dimensional geometry of nanotube aggregates and better tendency to form a conductive network with direct filler-filler contacts.