Experimental study on dielectric relaxation in alfa fiber reinforced epoxy composites

Abstract

Investigation on dielectric properties and behavior of thermoset epoxy composite based on cellulosic fibers has been carried on. Dielectric spectra were measured in the frequency range 0.1 Hz-100 kHz and at temperature intervals from ambient to 2008C. For the composite, four relaxations processes were identified, namely the orientation polarization imputed to the presence of polar water molecules in Alfa fiber, the a mode relaxation associated with the glass transition of the epoxy resin matrix, the relaxation process associated with conductivity occurring as a result the carriers charges diffusion noted for high temperature above glass transition and low frequencies, and interfacial or MaxwellWagner-Sillars relaxation that is attributable to the accumulation of charges at the Alfa fibers/epoxy resin interfaces. Dielectric relaxation analysis revealed evolution in water relaxation and it is thus concluded that the chemical treatment of the fiber can strongly influence the dielectrical properties and interfacial polarization processes in composites.

Effects of cellulose fiber content on physical properties of polyurethane based composites

“…The resulting space charge separation produces an increasing interfacial polarization. As a consequence, the dielectric constant of the composite increases, while the volume resistivity decreases, with cellulose loading [56][57][58][59], in agreement with the results of Figs. 10a and 10b.…”

“…For example, in kenaf fiber reinforced polyester composites, water diffusion coefficient largely increases beyond of 10 % of fiber weight fraction [61]. Chemical treatment with agents capable of enhancing the hydrophobicity of the natural fibers and/or creating chemical bonds at the matrix-fiber interface, reduces dielectric constant of the composite [56][57][58][59]. This confirms the role of water in the electrical properties such materials.…”

“…9 and 10), the effect of the internal or absorbed water molecules in cellulose cannot be excluded. Indeed, water molecules are known to be tightly bound to the surface hydroxyl groups of cellulose fibers and could not be removed irreversibly by a simple heat treatment [57,60]. For example, in kenaf fiber reinforced polyester composites, water diffusion coefficient largely increases beyond of 10 % of fiber weight fraction [61].…”

Studies on structural and electrical properties of ZnO/TiO 2 composite materials

“…In the frequency range of 10 Hz -10 3 Hz, a strong peak with relatively constant amplitude ( " M =0.1-0.12) appears and the frequency position varies with the increase of the TiO 2 content. This peak is commonly attributed to the interfacial polarization effects known as Maxwell-Wagner-Sillars (MWS) relaxation [55][56]. Its peak position changes with the composition content.…”

Effect of the interface treatment on the dielectric behavior of composite materials of unsaturated polyester reinforced by Alfa fiber

“…Over the past decade there has been a growing interest in the use of lignocellulosic fibers as reinforcing elements in polymeric matrix [1][2][3]. The specific properties of this natural product, namely low cost, lightweight, renewable character, high specific strength, availability in a variety of forms throughout the world, reactive surface and the possibility to generate energy without residue after burning at the end of their life-cycle motivate their association with organic polymers to elaborate composites materials.…”