Structure – properties relationships of graphene and spinel nickel ferrites based poly(vinylidene fluoride) hybrid polymer nanocomposites for improved dielectric and EMI shielding characteristics

Abstract

Hybrid polymer nanocomposites with poly(vinylidene fluoride) are prepared based on graphene and spinel nickel ferrites (nFE) nanoparticles to investigate their structure-properties relationships. X-ray diffraction and differential scanning calorimetry confirmed the co-existence of α- and β-crystal phases of PVDF by the incorporation of graphene and nFE whereas solely α- crystal phase formed in neat PVDF. The influence of graphene and nFE on the mechanical properties of PVDF is concentration dependant. The modulus of PVDF is enhanced ∼ 128% from 587 to 1340 MPa at the expense of reduction in failure strain from 18% to 6% in PVDF/graphene nanocomposite whereas in PVDF/graphene/nFE hybrid nanocomposites, the mechanical properties are reduced owing to the embrittlement. On the contrary, graphene-nFE-polymer interfacial space charge accumulation has caused the enhancement of dielectric and EMI shielding characteristics as a function of frequency (1kHz-5 MHz). In PVDF/graphene nanocomposites at 3 wt%, the dielectric constant (ε/) value is increased 16-fold while keeping the dielectric loss (ε//) values equivalent to neat PVDF. Whereas, both ε/ and ε// are increased enormously in PVDF/graphene/nFE hybrid nanocomposites along the whole frequency range. Similarly, EMI shielding (SET) of PVDF/graphene and PVDF/graphene/nFE is ∼ 16 and 22 dB, respectively for a film thickness of ∼0.2 mm. Comparatively, PVDF/graphene nanocomposites exhibited the synergistic balance in mechanical, dielectric and EMI shielding properties over PVDF/graphene/nFE hybrid nanocomposites.