Inclusione di materiali bidimensionali (2D) in matrici polimeriche

This work focuses on the inclusion of montmorillonite(MMT) and reduced graphene oxide (2D nanomaterials) in polyamide-imide(PAI) matrices. The challenge was to find specific methods to obtain a polymer nanocomposite with better and/or alternatives features compared to the standard polymer. PAI in general exhibits properties which can be attributed to the class of high-performance enamels. The effect of the nanomaterial inclusions on chemical resistance, thermal, mechanical and electric properties was investigated after a specific industrial application: magnet wire coating. For this purpose, nanocomposites were coated on the surface of copper wires and cured to form an electrical insulation film. In literature, several methods for a variety of polymer systems were widely investigated, except for PAI, on which there has been little research. Furthermore, the use of nanomaterials in polymeric matrices for copper wire applications still remains an unexplored field. In order to obtain polymer nanocomposite, two different methods have been used in this work: the solvent casting method and in situ polymerization. After the characterization of the 2D nanomaterials and the polymer, the first part of this thesis dealt with the nanocomposites synthesis of PAI-MMT modified with cationic surfactants of alkylammonium type [benzyl (hydrogenated tallow alkyl) dimethyl ammonium]. Surfactants provide an organophilic character to the silicates through a surface functionalization able to provide a good interaction with hydrophobic polymers. The introduction of groups characterized by a greater steric hindrance also has the advantage of spacing the platelets, facilitating the subsequent incorporation of the macromolecules. The physical separation of the silicate layers is an aspect of extreme importance, since only when completely exfoliated, nanocomposite can offer all its peculiar properties. In situ polymerization was performed by swelling MMT intergalleries with trimellitic anhydride (TMA) monomers followed by addition of MDI and subsequent polymerization to PAI within the intergalleries. The solvent casting method is based on swelling MMT intergalleries with solvent where the polymer is soluble (NMP in this case). Mixing of polymer and layered nanomaterial solutions results in intercalation of polymer chains and displacement of the solvent within the interlayers of silicates. With the approach of in situ polymerization, a new level of exfoliated particle concentration could be reached but in comparison, the solvent casting method turned out to be simpler and faster. In the second part of this work, reduced graphene oxide (rGO) was used instead of organoclay. The two methods previously described were also used for the synthesis of rGO-PAI nanocomposites. With in situ polymerization, a novel approach toward PAI-PE-rGO hybrid system (where PE indicates polyester) was developed. For this purpose, first rGO was covalently linked to the polyester (through the reaction with a dialcohol and a diacid in a 1:2 ratio, obtaining a polyester with terminal acid groups), then the PAI component was synthesized using these groups for the amide formation by reaction with MDI (methylenediphenyldiisocyanate). The success of covalent linking between rGO and polymer matrix was confirmed by the analysis of the acid number using the potentiometric method and FTIR. The MMT-PAI and rGO-PAI resins were then applied to the copper wire on which the control tests were performed. The last part of this dissertation focused on the synthesis of PAI-rGO nanocomposites (by solvent casting method) at different concentrations in order to obtain a light conductive resin. Even if a typical property of this kind of polymer is a good electrical insulation, it could be useful, for some applications, obtaining conductive properties. Subsequently, the varnishes were applied by means of a film applicator on tin-plate sheets and observed through an optical microscope and SEM.