On Nanographene-Reinforced Polyvinylidene Fluoride Composite Matrix for 4D Applications

In past two decades, number of studies has been reported on 3D printing of polyvinylidene fluoride (PVDF) composite matrix. But hitherto, little has been reported on 4D applications of graphene(Gr)-reinforced PVDF for maintenance and repair of heritage structures, especially for self-assembly applications. In this work, mechanical blending of Gr (size 5-10 nm)-reinforced PVDF has been reported for 4D applications as possible on-line maintenance tool for heritage structures. The Gr was blended in four different weight proportions in PVDF matrix. The effect of varying Gr proportion was studied on basis of rheological properties (melt flow index (MFI) and viscosity) required for processing on open source fused deposition modeling (FDM) setup. The various proportions/compositions of the composites were also investigated for thermal stability based upon differential scanning calorimetry (DSC) analysis (required for heritage structure). The selected proportion/composition of feed stock filament were processed on twin screw extruder (TSE) followed by mechanical testing on universal testing machine (UTM). The results of the MFI and viscosity outlined that blending of Gr in PVDF decreases the MFI and increases the viscosity of the composite matrix. The DSC testing showed that PVDF-10%Gr composite have heat capacity of − 64 J/g (during heating cycle). The maximum peak strength of 43.01 N/mm2 was observed, while processing at screw temperature 195 °C with 0.3 Nm torque for filament wire preparation. Finally the 3D printing of selected composition/ proportion was also successful. The piezoelectric properties of composite were observed after direct current (DC) poling by dielectric constant measurement (D33 = 45 pC/N), which is sufficient for self expansion/contraction properties. The feed stock samples prepared were counter verified by performing morphological analysis. For self-assembly applications, vibration sample magnetometry (VSM) was performed. The results are also supported by Fourier transformed infrared spectroscopy (FTIR) analysis for ascertaining bonding characteristics corresponding to observed mechanical properties.