Dielectric properties of thermoplastic elastomer/zinc oxide (ZnO) nanocomposites with controlled nanoparticles dispersion

In this study, the rheological and dielectric properties of two sets of nanocomposites prepared respectively from Styrene-Ethylene-Butylene-Styrene (SEBS) and SEBS grafted maleic anhydride (SEBS-g-MA) block copolymer matrices and surface functionalized zinc oxide nanoparticles have been investigated. The interaction at the polymer-nanoparticle interface was tuned through the MA graft in order to tailor the nanoparticles dispersion in the block copolymer nanostructure and to highlight its effect on the dielectric performance. Small Amplitude Oscillatory Shear (SAOS) measurements revealed highly improved solid-like behavior and a low frequency independent storage modulus in SEBS-g-MA based nanocomposite which indicates good dispersion and formation of a network between the nanoparticles and the polymer chains. This result was supported by a reduction in the adsorbed carbonyl peak in Fourier Transformed Infrared (FTIR) spectra attributed to an interaction between MA graft and the functional groups on the surface of ZnO nanoparticles. The dielectric spectroscopy revealed a limited increase of both real and imaginary parts of the dielectric permittivity and absence of interfacial relaxation peak, in the case of SEBS-MAZnO nanocomposite. Besides, the AC short term breakdown strength was slightly improved in the SEBS-MA-ZnO nanocomposite compared to the pure matrix while it decreased by 18% in SEBS-ZnO nanocomposite due to the presence of agglomerations.

I. Introduction

To improve the dispersion of metal oxide nanoparticles in polyolefin matrices, thermoplastic elastomers such as Styrene-Ethylene-Butylene-Styrene (SEBS) block copolymer were several times used as compatibilizers. Although better dispersion was generally achieved with these materials, few studies were reported on the specific dielectric characterization of thermoplastic elastomers/metal oxide nanocomposites, taking into consideration the possibility of controlled nanoparticles dispersion offered by the block copolymer ordered nanostructure [1]. In this study, the morphology, rheological and dielectric properties of nanocomposites of SEBS and SEBS grafted maleic anhydride (SEBS-g-MA) containing zinc oxide nanoparticles have been investigated. In particular, the potential effect of tailored interaction at the polymer-nanoparticle interface and selective nanoparticles dispersion in the block copolymer template on the dielectric properties has been emphasized. For that, functionalized nanoparticles exhibiting good affinity with maleic anhydride were used in order to improve the dispersion and to initiate the process of selective localization in the phase exhibiting the highest affinity.