Exploring the Potential Use of Clean Scrap PVDF as Matrix for Conductive Composites Based on Graphite, Carbon Black and Hybrids: Electromagnetic Interference Shielding Effectiveness (EMI SE)

Clean polyvinylidene fluoride scrap (rPVDF) from flexible oil pipelines was used as a matrix for the development of cost effective conductive composites. Carbon black (CB), expanded graphite (EG) and mixtures of both fillers were mixed with rPVDF in different compositions by melt processing. The influence of the conductive fillers on the electromagnetic interference shielding effectiveness (EMI SE) and microwave absorbing properties in the frequency range of X-band (8-12 GHz) was also investigated. Higher EMI SE was observed for the composite prepared with CB due to the higher conductivity. However, a synergistic effect was observed in both electrical conductivity and EM attenuation by reflection (reflection loss) by using hybrid materials. For composites containing 5 wt% of filler, that loaded with EG/CB (2:3 wt%) hybrid filler displayed higher attenuation of the EM (around 97%) at a frequency of 12.3 GHz. Increasing the CB in the hybrid, decrease the EM attenuation but the efficiency was observed in a broadband range, which is very important for stealth technology purpose. The influence of the fillers on the electrical, morphological and rheological properties of the composites was evaluated. Composite loaded with 7 wt% of the hybrid filler (EG/CB = 2:5 wt%) presented higher conductivity than that containing 7.5 wt% of CB but significantly lower viscosity, indicating outstanding processability. From scanning electron microscopy (SEM), it was possible to infer that the presence of CB in the hybrid promoted a better dispersion of EG, thus favoring the formation of the conducting pathway.