Development and characterization of graphane poly(vinyl alcohol) nanocomposites

The present research aims to develop multifunctional nanocomposite material that has the adequate electromagnetic interference (EMI) shielding properties with minimal thickness as well as good mechanical flexibility and particularly was easily processed into films. Graphene nanoplatelets (GNP) with unique extraordinary properties were preferred as reinforcement agent in the multifunctional polymer nanocomposite films development. Strategic combination of composite analytical testing approaches was essential in determining optimum composite material formulation consequently enhanced the maximum properties of nanocomposite film as the GNP dispersed homogeneously in the poly(vinyl alcohol) (PVA) matrix prepared by both solution casting (SC) and solution-impregnated electrospun nanofibrous (SI) methods. The first objective was to determine the tensile, thermal, and dynamic mechanical properties of resultant nanocomposite having different GNP size and loading content (1, 3, 5, 7wt%) prepared by solution casting (SC) method. Furthermore, second objective was to evaluate the microstructure of various GNP electrospun nanofibrous mat and to determine the thermal and dynamic mechanical properties of GNP nanofibrous mats/PVA (PVA/eGNP) nanocomposite films prepared by solution-impregnated electrospun nanofibrous (SI) fabrication method. The third objective was to compute the dielectric, attenuation and EMI shielding effectiveness (SE) values in the range of microwave frequencies. In this research, both types of GNP (GNP-M15 and GNP-C750) that incorporated into the PVA have enhanced their tensile strength and modulus of the resultant nanocomposites at low GNP loading but decreased when GNP loading beyond 5wt%. Conversely, the elongation at the break of the nanocomposites decreased with an incorporation GNP content. Additionally, nanocomposite incorporated with 3wt% of GNP C750 grade (43.33MPa) show 13% higher tensile strength compared to M15 grade. The storage modulus of PVA/GNP nanocomposites prepared by SC that incorporated with C750 and M15 GNP at 3wt% loading increased by 30% and 20% over the pure PVA film sample, respectively. The trend in dynamic mechanical properties (storage modulus) was in excellent agreement with the tensile characteristic. Moreover, the glass transition temperature, (Tg) in which significantly increased (10⁰C) was observed attributed to the better interaction of the GNP nanofillers with the PVA matrix. It was observed that the degree of crystallinity evaluated by DSC for the PVA/GNP nanocomposites incorporated with 1wt% of GNP loading was slightly increased (15.5%) compared to pure PVA (13.2%) and this supported with the additional confirmation by the XRD characteristic. Meanwhile, on the other hand the storage modulus of same GNP loading (3wt%) has shown an enhancement about 50% for the sample prepared by SI method. Furthermore, at the highest GNP loading (7wt%) of PVA/eGNP nanocomposite film has shown a comparable result to the optimum storage modulus (3wt%) obtained from PVA/GNP nanocomposite film. It was also found that the degradation temperature (Td) of the PVA/GNP nanocomposite was appeared at about 340˚C and it was about 10˚C increment compared to pure PVA. The PVA/GNP nanocomposites films show an enhancement up to 60% in dielectric properties at microwave frequencies range from 8GHz to 12GHz. The highest EMI SETotal of approximately 7.5 dB was achieved from 7wt% of GNP electrospun nanofibers mat reinforced PVA nanocomposite film which prepared by solution-impregnated electrospun nanofibrous method. These nanocomposite films which exhibited appropriate dielectric constant and attenuate electromagnetic wave due to dielectric losses were promising candidature for various shielding applications by tuning their filler content. The reinforced GNP electrospun nanofibrous have successfully utilized as a scaffold for multifunctional components of the resultant hierarchically organization nanocomposite with enhanced multifunctional properties.

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