Dielectric Properties of Paper Made from Pulps Loaded with Ferroelectric Particles

Hindawi Publishing Corporation Journal of Nanomaterials Volume 2016, Article ID 3982572, 10 pages http://dx.doi.org/10.1155/2016/3982572 Research Article Dielectric Properties of Paper Made from Pulps Loaded with Ferroelectric Particles Hind El Omari,1,2 Adel Zyane,1,2 Ahmed Belfkira,1 Moha Taourirte,1 and François Brouillette2 1 Macromolecular and Bioorganic Chemistry Laboratory, Faculty of Science and Technology, Cadi Ayyad University, Abdelkrim El Khattabi Avenue, P.O. Box 549, 40 000 Marrakesh, Morocco 2 Lignocellulosic Materials Research Center, Québec University at Trois-Rivières, 3351 Forges Boulevard P.C. 500, Trois-Rivières, QC, Canada G9A 5H7 Correspondence should be addressed to Ahmed Belfkira; Received 5 January 2016; Revised 2 March 2016; Accepted 11 April 2016 Academic Editor: Victor M. Castaño Copyright © 2016 Hind El Omari et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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 (BaTiO3 and 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. 1. Introduction The adoption of new legislations on environmental issues is limiting the widespread use of synthetic composites. As a result, researchers have been asked to develop biodegradable and renewable products. Thus, several materials based on natural products have emerged. Raw or modified lignocellulosic fibers are some of the most interesting materials because of their highly renewable character and high annual production (50 to 100 billion tons/year) [1]. The largest natural fiber consumer is by far the paper industry. Currently, in developing countries, about 60% of cellulose fibers arise from nonwood plants: bagasse, straw, alfa, flax, sisal, and so forth [2, 3]. The mechanical and electrical properties, surface finish, and porosity of paper made with these fibers depend on fiber extraction process, bleaching, cellulose content, fiber length and conformability, fiber source, presence of metal ions, moisture content, and manufacturing process [4–8]. More commonly used as a writing support and in packaging, paper has also been used in the electrical field as an insulator in power transformers and high voltage applications. Within a highly porous fibrous structure, the intimate surface of contact between the capacitor plates and the paper is very low; therefore, it is often used in the form of cardboard impregnated with mineral oil [1]. Indeed, paper has a low dielectric constant (between 1 and 2.5) with respect to pure cellulose (6 to 8.1) [7]. Thus, several lignocellulosic fibers/polymer matrices combinations were explored to find a composite with interesting properties. The objectives were to observe synergy between the properties of the matrix and fillers to simultaneously improve the strength of the material, electrical and sound insulation, and dielectric properties [9]. The dielectric properties of the paper can also 2 be improved by the addition of suitable fibers. The addition of synthetic fibers (polyacrylic) decreased the tangent angle of dielectric loss and improved mechanical properties. This type of paper was used as electrical insulation for cables [10– 12]. This does not always happen. Indeed, the introduction of TiO2 nanoparticles in the oil-impregnated paper reduces its constant and dielectric loss [13]. The dielectric properties of such materials change over time (decrease of the life cycle) as a result of cellulose chains depolymerization promoted by the presence of oxygen, moisture, and temperature variations [14–16]. A series of studies determined the electrical properties of paper made from agricultural residue pulps and their linseed oil-impregnated counterparts (e.g., rice straw paper, cotton stalks paper, and bagasse paper) [17–20]. These materials have shown interesting dielectric properties. This motivated more studies on the electrical properties of paper made from low cost and abundant plant materials [5]. In this study, the properties of paper made from plants fiber and commercial pulps were evaluated. The effect of the composition of the pulp and the introduction of ferroelectric particles in the presence of a retention aid on the mechanical and electrical properties was also discussed. The aim of this study is to show the potential of perennial plants as an electrical insulation material. These fibers show good insulating properties in addition to several advantages such as abundance, biodegradability, and ease of manufacture at low cost. 2. Experimental 2.1. Raw Materials 2.1.1. Lignocellulosic Fibers. Seven (7) different lignocellulosic pulps were used in this study. Five were extracted from plants growing on Moroccan soil [Halfa (Stipa tenacissima), Agave (Agave americana), Pennisetum (Pennisetum alopecuroides), Typha (Typha latifolia), and Junc (Juncus effusus)]. The two other samples were industrial pulps: bleached softwood Kraft and thermomechanical pulps (TMP) provided, respectively, by Kruger Inc.-Wayagamack and Kruger Inc.-Trois-Rivières mills (Canada). The plants were collected in the area of Kelaa Sraghna on the edge of the Lakhdar River. Pulps have undergone the same treatment. They were treated with sodium hydroxide (NaOH, 2%) and hydrogen peroxide (H2 O2 , 2%) at a temperature of 80∘ C for 8 h. This allowed the removal of hemicelluloses and lignin. After washing with distilled water to neutral pH, the fibers were dried in an oven at 60∘ C. The composition of each pulp, fines percentage, and length weighted average fiber length w (...truncated)