An economic and environment friendly process was adapted to synthesize new dielectric composite materials. Using ethylene vinyl acetate (EVA)/vinyl ester of versatic acid (VeoVa) terpolymer as an aqueous emulsion provides a homogenous dispersion of BaTiO 3 (BT) particles, due to the high viscosity and polarity of the vinyl resin (VR). Composites films were obtained from these dispersions by water evaporation. The evolution of the dielectric properties as a function of the BaTiO 3 content, was correctly fitted by a Maxwell-Garnett model. This fitting of the experimental curve shows a good dispersion of filler in the vinyl resin and the particles separation by a layer of resin as expected for the preparation method used in this study. The VR/BT composites show good synergy between the dielectric properties of the different phases of the composites due to the formation of macrodipoles and to the strong interactions between polar EVA/VeoVa groups and the BaTiO 3 particles surface. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44333.

Due to its physical properties and its ease of manufacture, paper is widely used in various engineering applications such as electrical insulation materials for components in high voltage technology. In this study, paper loaded with ferroelectric nanoparticles (BaTiO3and SrTiO3) was made with fibers obtained from plants growing on the Moroccan soil [Halfa (Stipa tenacissima), Agave (Agave americana), Pennisetum (Pennisetum alopecuroides), Typha (Typha latifolia), and Junc (Juncus effusus)] and two commercial pulps (bleached softwood Kraft and newsprint grade thermomechanical pulps). A retention aid, cation polyacrylamide (Percol 292), was necessary to retain ferroelectric particles in the fibrous network and improve the dispersion of strontium titanate particles. The different pulp and handsheets used were characterized according to standard methods (Pulp and Paper Technical Association of Canada, PAPTAC). It is well known that annual and perennial plants contain high percentages of fines (length < 0.2 mm) and short fibers. The results show that there is a strong interdependence between the dielectric properties of the loaded paper and surface finish, porosity, dispersion level of ceramic particles, fines content, shape, conformability, and sheet formation. The single dielectric relaxation detected towards low frequencies is attributed to hydroxyl groups present on fiber surfaces, in ceramic particles and adsorbed water.

This work aims to investigate the dielectric potential of microcrystalline cellulose, a green biosourced material, as a third constituent in the three-phase composites based on ethylene vinyl acetate-vinyl ester of versatic acid (EVA-VeoVa) terpolymer and BaTiO 3 . For that, new green three-phase composites were prepared using an economic and green process, with simple implementation at room temperature and using water as a solvent. Compared with the binary composite EVA-VeoVa/BaTiO 3 , the three-phase composite EVA-VeoVa/BaTiO 3 /microcrystalline cellulose showed an improvement of the BaTiO 3 particles dispersion, enhanced relative permittivity, and reduced dielectric loss, which explains the significance of this study. V C 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46147.Figure 6. Schematic microstructures of VR/BT (0 wt % of MCC) and of the three-phase composites VR/BT/MCC (1 and 4 wt % of MCC). [Color figure can be viewed at wileyonlinelibrary.com] ARTICLE WILEYONLINELIBRARY.COM/APP