Hybrid nanocomposites of poly (styrene-b-ethylene-ran-butylene-b-styrene) (SEBS), graphene nanoplatelets (GnP), and carbon nanotubes (CNT) were successfully prepared by melt compounding for electromagnetic shielding applications. The morphologies of the carbon nanoadditives and nanocomposites were investigated by Raman spectroscopy, field emission gun scanning electron microscopy, and rheological analysis. DC electrical conductivity was assessed by two-probe and four-probe techniques. Electromagnetic interference shielding effectiveness, shielding mechanisms, and dielectric properties were conducted in the X-band microwave frequency range (8.2-12.4 GHz). The results showed that CNT had a higher affinity with the matrix, and were better dispersed than GnP. SEBS/GnP/CNT nanocomposites induced an electrical conductivity increase of 17 orders of magnitude compared to the polymer matrix. The hybrid nanocomposites presented synergic effects on EMI-SE when compared to the singlecomponent nanocomposites (SEBS/GnP and SEBS/CNT). The maximum EMI-SE of 36.47dB (reduction of 99.98% of the incident radiation) was achieved for the SEBS/GnP/CNT nanocomposite with 5/10 wt.% of GnP/CNT, respectively. All the hybrid nanocomposites with CNT loadings equal to or higher than 8 wt.%. presented the required EMI-SE for commercial applications.
Poly(vinylidene fluoride) (PVDF) nanocomposites with different ferrite nanoparticle loadings are interesting as, depending on ferrite type and content, the electroactive β-phase of the polymer is nucleated and the magnetoelectric coupling is induced. The isothermal crystallization behavior of ferrite/PVDF nanocomposites is studied using polarized optical microscopy, and the crystallization kinetic is analyzed by the Avrami theory in order to understand the crystallization conditions leading to the nucleation of the electroactive polymer phase. It is found that the nucleation kinetics is enhanced by the presence of ferrite nanoparticles, as evidenced by the increasing number of spherulites with increasing nanoparticle content and by the variations of the Avrami exponent. The crystallization velocity is intimately related to the polymer α- or β-phase formation in the nanocomposites and follows the order NiFe(2)O(4)/PVDF > CoFe(2)O(4)/PVDF > Ni(0.5)Zn(0.5)Fe(2)O(4)/PVDF for a given temperature and nanoparticle loading, which results in larger amounts of β-phase for CoFe(2)O(4)/PVDF and Ni(0.5)Zn(0.5)Fe(2)O(4)/PVDF nanocomposites.
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