Influence of Biodegradable Poly(lactic acid) in Poly(vinylidene fluoride)-Based Conducting Multifunctional Blend Nanocomposites on the Structure, Morphology, Electrical, Electromagnetic Interference Shielding, and Piezoelectric Properties

This study explores the influence of biodegradable poly(lactic acid) (PLA) when blended with poly(vinylidene fluoride) (PVDF) and expanded graphite (ExGr) on the electrical, electromagnetic interference shielding effectiveness (EMI SE), and piezoelectric properties of the blend nanocomposites. Temperature-gradient-introduced compression molding of neat PVDF and PVDF-x wt % PLA (x = 10, 20, 40) films results in the generation of the beta-phase of PVDF along with gamma- and alpha-phases. The compression-molded neat PVDF film exhibits a higher beta-phase content in comparison to the PVDF-PLA blend and blend nanocomposites. The electrical conductivity increases for blend nanocomposites with higher PLA loading due to enhanced dispersion of graphite nanosheets, as evidenced through the FESEM analysis of selected samples. The impedance and the real part of relative permittivity analyses of blend nanocomposites support enhanced dispersion of ExGr particles with an increase in the PLA content in the blend. In finger tapping mode, the maximum output voltage of 2 V (average voltage of 1.5 V) is obtained for PVDF-10 wt % PLA-9 wt % ExGr hybrid nanocomposites due to the higher electroactive phase content. The total EMI SE of 0.2 mm thick PVDF-40 wt % PLA-9 wt % ExGr blend nanocomposite film obtained is 34 dB at 10 GHz, which is dominated by the absorption process. The EMI SE obtained in this work is better than those of many PVDF-based foams and aerogels. Thus, the blend nanocomposites hold promise in microwave absorption and piezoelectric nanogenerator applications.