Influence of chitin nanocrystals on the dielectric behaviour and conductivity of chitosan-based bionanocomposites

Publication date: Available online 21 August 2018Source: Composites Science and TechnologyAuthor(s): A.M. Salaberría, R. Teruel-Juanes, J.D. Badia, S.C.M. Fernandes, V. Sáenz de Juano-Arbona, J. Labidi, A. Ribes-GreusAbstractA series of bionanocomposite films based on chitosan, reinforced with chitin nanocrystals, were developed, and assessed in terms of dielectric behavior and conductivity by using an experimental methodology that allows avoiding the conductivity contribution and the exclusion of contact and interfacial polarization effects. The dielectric relaxations at low and high frequency and temperatures were modeled by Havriliak-Negami functions. Below the glass transition temperature (Tg), the γ and β relaxations were observed, which were related to intramolecular and non-cooperative segmental movements. At higher temperatures, an intermolecular and cooperative macromolecular movement, related to the glass transition, gave rise to α-relaxation. In addition, two over-Tg ρI and ρII relaxations were found, which were related to the displacement of dipoles in the disordered structure of bionanocomposites. The addition of chitin nanocrystals did not affect the apparent activation energy Ea of the γ-relaxation. However, it decreased the Ea of the β-relaxation and increased the free volume at temperatures in the vicinities of the α-relaxation. Finally, the electric conductivity of the bionanocomposites was lower than that of neat chitosan and chitin due to the int...

Source: Composites Science and Technology - August 21, 2018 Category: Science Source Type: research