Abstract:
The development of radar absorbing materials is a flourishing field of research in both the commercial and defense sectors for stealth technology. In this research work, three phase system is prepared, having the insulative matrix blended with conductive matrix that is further embedded with Nano filler. Polyaniline (PANI) is synthesized using emulsion method, containing the conductive character. Polyvinyl alcohol (PVA), semi-crystalline in nature, is chosen as an insulator matrix and few layer graphene (FLG) is incorporated as a Nano filler in the PVA/PANI blend. Various concentrations of PVA/PANI blends were prepared and in selected blend concentrations, FLG is incorporated up to 1 wt%. Polymer blend of PVA/PANI and Hybrid composite of PVA/PANI/FLG are prepared via solution casting method and characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), extensometer, impedance analyzer and microwave absorption test. PANI forms a heterogeneous immiscible phase with PVA matrix confirmed by XRD and SEM. FLG is dispersed uniformly in the PVA/PANI blend, although at concentrations up to 0.5 wt% of FLG, the sample shows exfoliation of graphene layers in the blend matrix but at 1.0 wt% of FLG, some agglomerations started to form.
The tensile strength of PVA is decreased up to 64 % from 29.3 to 8.5 MPa with increasing concentration of PANI owing to the disruption of the packing of PVA chains in the presence of PANI. By the addition of FLG in PVA/PANI blends, the tensile strength is increased up to 75% from 29.3 to 51.5 MPa and similarly the modulus is increased up to 1017 % from 0.17 to 1.9 GPa, inducing the reinforcement effect of FLG by anchoring the polymer chains. Similarly, the dielectric properties are significantly enhanced for the PVA/PANI/FLG system in which dielectric constant is increased from 4 to 8000 and dielectric loss is increased from 0.5 to 500000 at 100 Hz. The microwave absorption test revealed that the material having highest dielectric loss showed the highest value of absorption up to 21.3dB at 18.3GHz. The promising mechanical and dielectric results of PVA/PANI/FLG make it a suitable system for microwave and radar absorption applications.
