Flexible microwave absorbing composites based on polydimethylsiloxane filled with hybrid carbonaceous materials: Statistical analysis of the synergistic effect

The effect of the combination of carbon nanotubes (CNT) and graphene nanoplatelets (GNP) on the electromagnetic absorbing properties of polydimethylsiloxane (PDMS) composites was investigated. Samples were prepared by a low-cost and scalable simple one-step blending approach. The number of experiments and sample compositions were optimized by design of experiments (DOE) technique, namely, Axial Simplex Centroid. The samples were analyzed concerning rheology, electric conductivity and electromagnetic properties, such as absorptivity (reflection loss - RL). CNT was revealed to be more efficient than GNP in structuring the conductive network of filler particles. On the other hand, the hybrid filler composite with a 1:1 ratio (CNT/GNP = 0.67%:0.67%) presented the highest electric conductivity (3.53 x 10(-3) S m(-1)) and the best overall electromagnetic results, with measured RL reaching -25 dB and effective absorption bandwidth frequency of 4.6 GHz, with sample 2 mm thick. The best calculated RL value for this sample was observed with 2.5 mm with RL value corresponding to -46.8 dB. The special cubic polynomial model was successfully adjusted to the experimental data and statistically proved the synergistic effect of the hybrid on the electromagnetic properties of PDMS composites. Finally, PDMS/CNT/GNP composites were successfully prepared by a simple, fast and inexpensive method.