Studies on conductive polymer composites for advanced aerospace applications

Presently, there is an immense interest in multifunctional materials such as those having both electrical and magnetic properties, a critical requirement in certain advanced aerospace and defence applications. Intrinsically Conducting\ud Polymers (ICPs) and their Nanocomposites have emerged as a class of such materials experiencing exponential growth today. The Polypyrrole (PPy)/Fe3O4 Nanocomposites represent one of the most sought after multifunctional materials\ud being investigated. In this research work, PPy/Fe3O4 Conducting Polymer Nanocomposites (CPNCs) containing different wt. % (0- 16.52%) of Fe3O4 nanoparticles, were in-situ synthesized using chemical oxidative polymerisation\ud in an aqueous solution of FeCl3.6H2O (oxidant cum dopant) at higher molar ratios of oxidant to monomer (10:1). These CPNC powders were variously characterized through a 4 Probe electrical conductivity measurement technique, Fourier Transform Infra Red spectroscopy (FTIR), Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA) and Vibrating Sample Magnetometer (VSM). Results showed an increase of electrical conductivity (σ) from 45 S/cm for the unmodified PPy, up to a maximum of 75.28 S/cm for the 2.52% Fe3O4 loaded CPNC, with improved thermal stability compared to the host PPy. Also the saturated magnetization MS of the CPNC powders increased linearly with\ud Fe3O4 loading. iv Further, to demonstrate the racticability of the application potentials of the research outcome, composite films were also developed by dispersing the 2.52%\ud Fe3O4 loaded CPNC (optimum) particles in a clear Polyurethane (PU) paint matrix. These conductive polymer films prepared with varied CPNC loadings (0-4% by weight) by spray coating onto a Polyethylene substrate, were also\ud characterized by the 4 probe electrical conductivity measurement technique, FTIR, DSC (Differential Scanning Calorimetry), TGA, VSM and a Universal Testing Machine (UTM). Results showed that the conductivity (σ) reached a\ud maximum of 7.413*100 S/cm for the 4% wt.% optimized - CPNC loaded PU composite, which also exhibited a good sprayable consistency. FTIR analysis of the CPNC-PU films, showed a shift in the chemical peaks of the host polymer to higher wave numbers, revealing the influence of nanoparticles present in the host polymer. DSC thermograms clearly brought out the variations in thermal transitions occurring in the CPNC-PU films, with increased CPNC loading.\ud Further, the TGA analysis confirmed increased thermal stability, while VSM measurements showed increased Saturated Magnetization MS, with increased CPNC loading in the films. The tensile strength of the composite PU film is\ud decreased by 15.48% and the % strain increased by 164.74% at 4% CPNC loading in the film