writer：Estrella Laredo, Alfredo Bello, Jonas Diaz, Mario Grimau, Daniel Martinez-Tong, Defeng Wu and Liang Wu
keywords：Polylactide, Carbon Nanotube, Composites, Crystallization, Conductivity
source：期刊
specific source：Polymer Composites
Issue time：2013年

Polymer Composites, 2013, 34(1), 67-76

ABSTRACT:

 After DC and AC conductivity measurements, percolation parameters, universality, and time-temperatureconcentration superposition are evaluated in biocomposites
based on poly(lactide) loaded with multiwalled carbon nanotubes either carboxylic, PLA/c-CNT, or pure but with a larger aspect ratio, PLA/LAR-CNT, in weight
concentrations up to 7%. The polymer matrix is either 100% amorphous or cold-crystallized. Wide angle X-ray scattering is used to extract the crystallinity at each
temperature. The nucleating effect for the cold crystallization of the PLA is greater for the LAR-CNT than for the carboxylic ones. DC and AC conductivities are
measured in broad frequency and temperature ranges, from 1 mHz to 1 MHz and from 133 to 378 K, respectively. The critical percolation value increases for c-
CNTs (from 1.8 to 2.4 vol%) upon cold crystallization of the PLA matrix as the formation of a conductive path is hindered by the existence of a crystalline phase, which is dominant over the reduction of the amorphous regions. No significant changes upon crystallization were found in the critical concentration value (0.6 vol%)
for the LAR composites, where the conductive path is 2D. The universal scaling found here for different concentrations is lost when temperature varies. However,
time-temperature superposition is present for each concentration of LAR or carboxylic CNTs.

PDF DOWNLOAD:

 http://onlinelibrary.wiley.com/doi/10.1002/pc.22378/abstract