Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj Macromolecular Nanotechnology Thermoplastic elastomer nanocomposites with controlled nanoparticles dispersion for HV insulation systems: Correlation between rheological, thermal, electrical and dielectric properties Emna Helal a , Eric David a , Michel Fréchette b , Nicole R. Demarquette a, ⁎ a Mechanical Engineering Department, École de Technologie Supérieure ÉTS, Montréal, QC, Canada b Institut de Recherche d’Hydro-Québec IREQ, Varennes, QC, Canada ARTICLE INFO Keywords: Thermoplastic elastomer Nanodielectric Tailored dispersion Rheological percolation HV insulation ABSTRACT Thermoplastic elastomer nanocomposites based on respectively polystyrene-b-poly(ethylene-co- butylene)-b-polystyrene (SEBS) and polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene grafted maleic anhydride (SEBS-MA) block copolymers and containing functionalized zinc oxide (ZnO) nanoparticles have been investigated as candidate materials for high voltage (HV) in- sulation systems. The dispersion of the organically modified ZnO nanoparticles has been suc- cessfully tuned through the MA graft and the block copolymer nanostructure. In particular, na- nocomposites with signs of rheological percolation, indicating the formation of a network between individually dispersed nanoparticles and polymer chains, have been obtained at ZnO content as low as 5 wt% (0.9 vol%). This behavior resulted in an enhancement of the thermal conductivity and better control of the electrical conductivity while maintaining breakdown strength and dielectric losses in the same range of the unfilled insulating matrices. Furthermore, the resistance to surface erosion by partial discharges was significantly improved: in the presence of 5 wt% of individually dispersed ZnO nanoparticles, the eroded volume was reduced 10 times. 1. Introduction Due to the immiscibility of their blocks that are covalently bonded, block copolymers can self-organize into spherical, cylindrical, lamellar or more complex ordered nanodomains, depending on several parameters such as the block copolymer composition, the chemical interaction between the blocks and the molecular weight [1]. Owing to this nanostructure, several block copolymers, including polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) and polystyrene-b-poly(ethylene-co-butylene)-b-poly- styrene grafted maleic anhydride (SEBS-MA) thermoplastic elastomers, have recently attracted considerable attention as template matrices offering the possibility of nanoparticles dispersion control, in the aim of producing nanocomposites and master batches with tailored dispersion and interphase region. The expected high performance materials have a great potential in different applications including dielectric applications [2,3]. However, to the best of our knowledge, only few studies reported specific dielectric char- acterization of thermoplastic elastomeric block copolymer based nanocomposites [4–9], taking into consideration the possibility of tuned nanoparticles dispersion, in the aim of producing high performance nanodielectrics [2,3,8]. In addition to the nanoarchitecture, thermoplastic elastomeric block copolymers can play a functional role in dielectric appli- cations such as dielectric elastomer actuators and HV insulation materials. In fact, these materials exhibit good mechanical properties combining both elastomer and thermoplastic properties [10,11], good electromechanical coupling [12] as well as good resistance to http://dx.doi.org/10.1016/j.eurpolymj.2017.06.038 Received 28 February 2017; Received in revised form 18 June 2017; Accepted 24 June 2017 ⁎ Corresponding author. E-mail address: nicoler.demarquette@etsmtl.ca (N.R. Demarquette). European Polymer Journal 94 (2017) 68–86 Available online 27 June 2017 0014-3057/ © 2017 Elsevier Ltd. All rights reserved. MARK