Síntese e caracterização do polímero condutor polipirrol e do compósito condutor de polipirrol/caulinita/epóxi para aplicação em material absorvedor de radiação eletromagnética

Abstract

Intrinsically conductive polymers (ICP) are promising materials for application in electromagnetic radiation absorbing materials (RAM) since they are light materials with good mechanical and electrical characteristics, high electrical conductivities, oxidation resistance, and simple synthetic route. They can reach conductivities very close to inorganic semiconductors and are easy to obtain with low production costs; however, they are materials that are difficult to process in the RAM matrix due to their low solubility and fusibility. In this context, different synthesis variables were used to synthesized the material in this work in order to improve the processability characteristics of the polymer in the epoxy resin matrix and achieve good values of incident wave attenuation of the final material in the X band (8.2 to 12.4 GHz). In this context, this work presents a study of the conductive polymer polypyrrole (PPy) and organic-inorganic composite of PPy with natural clay mineral kaolinite (PPy/Kao), where different synthesis variables were used in order to improve the processability characteristics of the polymer in the epoxy resin matrix and achieve good values of incident wave attenuation of the final material in the X band (8.2 to 12.4 GHz) PPy was obtained by chemical synthesis using doping agents: hydrochloric acid (HCl), lauric acid (LA), and sodium dodecyl sulfate (SDS) with a dopant/monomer ratio of 1:2.The PPy/Kao nanocomposites were produced via in situ polymerization, where the same experimental conditions of the pure PPy synthesis were applied, adding to the reactions kaolinite ratios at concentrations of 1 and 3% by mass. Neat PPy and PPy/Kao were polymerized, and epoxy matrix composites were prepared with the synthesized polymers.The RAM composites were obtained by mechanically mixing the epoxy matrix with the synthesized materials in the proportion of 1.0% m/m (polymer/epoxy). The characterization was performed by fourier transform infrared spectrometer (FT-IR), scanning electron microscopy (SEM), thermogravimetry analysis (TGA), X-ray diffraction (XRD), electrical conductivity analysis, and electromagnetic measurements in the band X. The results showed that the obtained RAM presented a good performance as an electromagnetic wave absorber, with thermal stability above 120 o C and incident wave attenuation ranging from -10 to -30 dB in the X band.