Room-Temperature Ferromagnetic Sr3YCo4O10+δ and Carbon Black-Reinforced Polyvinylidenefluoride Composites toward High-Performance Electromagnetic Interference Shielding

In this study, we fabricated composites of conducting carbon black (CB), room-temperature ferromagnetic Sr₃YCo₄O_10+δ (SYCO) and polyvinylidenefluoride (PVDF) by the solution mixing and coagulation method for the first time. During the nucleation process of PVDF, the presence of SYCO and CB individually facilitates the crystallization of polar β and semipolar γ phases along with the nonpolar α phase in PVDF. The dc electrical conductivity of PVDF raised from 1.54 × 10^-8 to 9.97 S/m with the addition of 30 wt % of CB, and it is nearly constant with respect to the SYCO content. The PVDF/CB/SYCO composites (PCS) possess high permittivity and its variation is in accordance with the content of polar phases in PVDF. Moreover, the complex permittivity and permeability spectra from 10 MHz to 1 GHz indicate that the dielectric loss dictates over magnetic loss in these composites. The electromagnetic interference shielding effectiveness (EMI SE) of PCS composites is higher than that of PVDF/CB and PVDF/SYCO composites in the 8.2-18 GHz region. Addition of SYCO in the PVDF/CB matrix enhances shielding by dominated absorption with minimal reflection. The analysis of the shielding mechanism suggests that in addition to conducting and magnetic losses due to CB and SYCO, respectively, the synergy among CB, SYCO, and PVDF promotes shielding by matching the input impedance to that of free space, enhancing multiple internal reflections from SYCO and subsequent absorption by CB, eddy current losses, dielectric damping losses, interfacial polarization losses, and so forth. These different mechanisms result in an enhanced EMI SE of 50.2 dB for the PCS-40 composite for a thickness of 2.5 mm.

Crystallographic features of poly(vinylidene fluoride) film upon an attractive substrate of KBr

Among all the polymorphs of poly(vinylidene fluoride) (PVDF), the polar γ-form possesses the highest melting point and electrical breakdown strength as well as the strongest solvent and irradiation resistance, which are beneficial for the durability of PVDF products.

A facile method to enhance ferroelectric properties in PVDF nanocomposites

PVDF/Nanoclay physical compatibilization a facile method to enhance ferroelectric properties.

Effects of dynamic vulcanization on the kinetics of isothermal crystallization in a miscible polymeric blend

Is it possible to determine the state of phase separation using the free energy of folding parameter?

Enhanced ferroelectric properties of electrospun poly(vinylidene fluoride) nanofibers by adjusting processing parameters

This contribution investigates the ferroelectric properties and polymorphism evolution of poly(vinylidene fluoride) (PVDF) mats prepared through electrospinning solutions of PVDF in pure N,N-dimethylformamide (DMF) and DMF/acetone mixtures with different weight ratios.

Influence of miscibility phenomenon on crystalline polymorph transition in poly(vinylidene fluoride)/acrylic rubber/clay nanocomposite hybrid

In this paper, intercalation of nanoclay in the miscible polymer blend of poly(vinylidene fluoride) (PVDF) and acrylic rubber(ACM) was studied. X-ray diffraction was used to investigate the formation of nanoscale polymer blend/clay hybrid. Infrared spectroscopy and X-ray analysis revealed the coexistence of β and γ crystalline forms in PVDF/Clay nanocomposite while α crystalline form was found to be dominant in PVDF/ACM/Clay miscible hybrids. Flory-Huggins interaction parameter (B) was used to further explain the miscibility phenomenon observed. The B parameter was determined by combining the melting point depression and the binary interaction model. The estimated B values for the ternary PVDF/ACM/Clay and PVDF/ACM pairs were all negative, showing both proper intercalation of the polymer melt into the nanoclay galleries and the good miscibility of PVDF and ACM blend. The B value for the PVDF/ACM blend was almost the same as that measured for the PVDF/ACM/Clay hybrid, suggesting that PVDF chains in nanocomposite hybrids interact with ACM chains and that nanoclay in hybrid systems is wrapped by ACM molecules.