Abstract

BELLO, Alfredo; GRIMAU, Mario  and  LAREDO, Estrella. Electrical conductivity in polymer/carbon nanotube nanocomposites in PCL and PCL/PLA blends. Rev. Fac. Ing. UCV [online]. 2014, vol.29, n.1, pp.127-132. ISSN 0798-4065.

DC and AC conductivities of bionanocomposites based on a polymer matrix such as Poly(ε-caprolactone), PCL, or on the polymer blend PCL/PLA (Polylactide) with multi-walled carbon nanotubes, CNT, as a nanofiller, have been studied in wide frequency ( 10^-3 Hz to 1 MHz) and temperature (133 to 323 K) ranges. These matrices were loaded with multi-walled carbon nanotubes, CNT, up to a concentration of 4 % in weight. X-Ray diffractograms showed that PCL was always semi-crystalline with an orthorhombic structure, spatial group P2₁2₁2₁. The crystallinity degrees were estimated to 46 % for neat PCL and 55 % for PCL in the blend. The minority phase, PLA, due to its higher viscosity, excluded the CNT which were selectively located in the PCL phase and decorating the interphases. The adhesion among the two blend components was drastically improved in the CNT presence. Molecular dynamics at different scales, local or segmental, were studied through the dielectric spectrum obtained for low concentrations, below the percolation threshold. No differences were observed among neat PCL and the blend, thus confirming the blend immiscibility. The Universal Dynamic Response proposed by Jonscher, which explains conductivity behavior, either ionic or electronic, was applied to describe the results in the whole frequency range. The parameters characteristic of the percolation process were determined for both nanocomposites and the threshold values were found to be 1 wt% for the blend and 0.3 % for neat PCL. In both cases an important contribution to the conductivity through carrier tunneling among CNT not yet in physical contact was evidenced. Also, differences in the validity of the universal curves were observed: only in neat PCL time-temperature-concentration superposition existed.

Keywords : Nanocomposites; Carbon nanotubes; Percolation; Loaded polymers; Polymer blends; Poly(-caprolactone); Polylactide.

        · abstract in Spanish     · text in Spanish     · Spanish ( pdf )