Dynamic rheological studies of poly(p-phenyleneterephthalamide) and carbon nanotube blends in sulfuric acid

Abstract

We have studied the dynamic scanning of liquid-crystalline (LC) poly(p-phenyleneterephthalamide) sulfuric acid (PPTA-H2SO4) solution, and its blend with single-walled carbon nanotubes (SWNTs), by using a flat plate rotational rheometer. The effects of weight concentration and molecular weight of PPTA, as well as operating temperature, on dynamic viscoelasticity of the PPTA-H2SO4 LC solution system are discussed. The transition from a biphasic system to a single-phase LC occurs in the weight concentration range of SWNTs from 0.1% to 0.2%, in which complex viscosity reaches the maximum at 0.2 wt% and the minimum at 0.1 wt%, respectively, of SWNTs. With increasing SWNT weight concentration, the endothermic peak temperature increases from 73.6 to 79.9 °C. The PPTA/SWNT/H2SO4 solution is in its plateau zone and storage modulus (Ǵ) is a dominant factor within the frequency (ω) range of 0.1-10 rad/s. As ω increases, the Ǵ rises slightly, in direct proportion to the ω. The loss modulus (G{double acute}) does not rise as a function of ω when ω < 1 s-1, then when ω > 1 s-1 G {double acute} increases faster than Ǵ, yet not in any proportion to the ω. © 2010 by the authors.