PSI - Issue 10

A. Sanida et al. / Procedia Structural Integrity 10 (2018) 91–96

95

A. Sanida et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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(a)

(b)

Fig. 4. Variation of real (a) and imaginary (b) part of dielectric permittivity as a function of frequency, for all the examined systems, at 40 o C.

4. Conclusions

In the present study Fe 3 O 4 /PVDF nanocomposites were prepared and studied varying the reinforcing phase content. Storage modulus was found to increase systematically with filler content in the whole temperature range of the tests. The peak position of the broad peaks recorded in the loss modulus spectra indicate the transition associated with molecular motion of amorphous parts restricted within the crystalline region or various defect types in crystals and in the crystalline/amorphous interface, which seems not to be significantly affected by the presence of nanofiller. Young’s modulus increases in general with the concentration of Fe 3 O 4 and tensile strength initially increases and consequently diminishes with increasing filler concentration. DSC studies gave indications for the polymorphic character of PVDF and decrement of melting temperature with filler content. Dielectric spectra revealed the presence of three relaxations processes, glass-rubber transition ( α α -relaxation) of PVDF, α c -process attributed to the amorphous phase restricted in the crystalline phase, or to defects and chain loops or twisting, and space-charge polarization and charge motion within the material related with conductivity and/or interfacial polarization. Bello, A., Laredo, E., Grimau, M., 1999. Distribution of relaxation times from dielectric spectroscopy using Monte Carlo simulated annealing: Application to α−PVDF . Physical Review B 60(18), 12764-12774. Bhatt, A.S., Bhat, D.K., Santosh, M.S., 2011. Crystallinity, conductivity, and magnetic properties of PVDF-Fe 3 O 4 composite films. Journal of Applied Polymer Science 119, 968-972. Frickel, N., Gottlieb, M., Schmidt, A.M., 2011. Hybrid nanocomposites based on superparamagnetic and ferromagnetic particles: A comparison of their magnetic and dielectric properties. Polymer 52, 1781-1787. Kepler, R.G., Anderson, R.A., 1978. Piezoelectricity and pyroelectricity in polyvinylidene fluoride. Journal of Applied Physics 49, 4490-4494. Linares, A., Nogales, A., Rueda, D.R., Ezquerra, T.A., 2007. Molecular dynamics in PVDF/PVA blends as revealed by dielectric loss spectroscopy. Journal of Polymer Science: Part B: Polymer Physics 45(13), 1653-1661. Lovinger, A.J., 1982. Annealing of poly(vinylidene fluoride) and formation of a fifth phase. Macromolecules 15, 40-44. MacDonald, J.R., 1987. Impedance spectroscopy. Wiley, New York. Patsidis, A., Psarras, G..C., 2008. Dielectric behaviour and functionality of polymer matrix – ceramic BaTiO 3 composites. Express Polymer Letters 2(10), 718-726. Prabhakaran, T., Hemalatha, J., 2013. Ferroelectric and magnetic studies on unpoled Poly (vinylidine Fluoride)/Fe 3 O 4 magnetoelectric nanocomposite structures. Materials Chemistry and Physics 137, 781-787. Psarras, G.C., 2010. Conductivity and dielectric characterization of polymer nanocomposites , in “ Polymer Nanocomposites: Physical Properties and Applications ”. In: Tjong, S.C., Mai Y.M., (Ed.). Woodhead Publishing Limited, pp. 31-107. Ramajo, L.A., Cristóba l, A.A., Botta, P.M., Porto López, J.M., Reboredo, M.M., Castro, M.S., 2009. Dielectric and magnetic response of Fe 3 O 4 /epoxy composites. Composites A 40, 388-393. References