Preparação e caracterização de nanocompósitos de polipirrol e nanofibra de celulose incorporados com grafeno e nanopartículas de ferro (II) e manganês (II)

Abstract

The development of new materials that are more economical, efficient and environmentally sustainable with the most varied purposes in different areas are gaining prominence. In this way, the association of natural and conductive polymers has shown promise, such as cellulose nanofiber (CNF), a renewable and biodegradable polymer, which has good mechanical properties that can be added to the materials to which it is incorporated, and the polypyrrole, a conductive polymer that presents electrical properties of semiconductor materials and can be associated with other materials. Several studies have been proposing numerous applications for these materials, such as electromagnetic shielding, capacitors, electronic devices and biosensors. The combination of these polymers makes it possible to develop conductive films with excellent mechanical properties. This work aims to produce a nanocomposite based on cellulose nanofiber (CNF), supplied by the company Suzano, and polypyrrole, also incorporating different concentrations of graphene oxide and magnetic nanoparticles of iron and manganese oxide, and to observe the effects that the different concentrations of these components generate. Polypyrrole was synthesized chemically in the presence of cellulose nanofibers. The reduced graphene oxide was produced by the modified Hummers method, exfoliated in an ultrasound processor and reduced with hydrazine. The magnetic nanoparticles (MNP) of iron and manganese were synthesized from manganese and iron chloride. After the synthesis, the conductive membranes were prepared following a factorial design varying the composition of reduced graphene oxide and magnetic nanoparticles (MNP), in percentages from 0.54% to 17.46% by mass, and then filtered and hot pressed. The morphology of the membranes and their pure components were characterized by scanning electron microscopy (SEM), the electric conductivity of the membranes was characterized in a four point probing system, and an electromagnetic shielding performance was evaluated in 0.04 mm thick films in the frequency range of 8.2 to 12.4 GHz (X-band). The SEM images showed a homogeneous mixture, where the polypyrrole coated the cellulose nanofibers. From the measure of four points a conductivity value of 17.1705 (Ω.m)-1 was obtained in the condition that contained 17.46% graphene and 9.00% MNP, classifying the material as a semiconductor. As the graphene content increases, there was an increase in conductivity values, on the other hand, MNPs do not influence these values. In the electromagnetic barrier study, the maximum shielding effectiveness was -9.13 decibels at 8.2 GHz in the thickness of 0.04 mm, in the condition that contained 17.46% graphene and 9.00% MNP. It was observed that higher the graphene content greater was the shielding effectiveness. Such results obtained indicate that material has potential for future applications in electromagnetic interference shielding materials or electronic devices for energy storage.