Rheological properties and crystallization behavior of multi-walled carbon Nanotube/Poly(ε-caprolactone) composites

Multi-walled carbon nanotube/poly(epsilon-caprolactone) composites (PCLCNs) were prepared by melt compounding. The rheology, nonisothermal crystallization behavior, and thermal stability of PCLCNs were, respectively, investigated by the parallel-plate rheometer, differential scanning calorimeter, and TGA. Cole-Cole plots were employed successfully to detect the rheological percolation of PCLCNs under small amplitude oscillatory shear. PCLCNs present a low percolation threshold of about 2-3 wt % in contrast to that of clay-based nanocomposites. The percolated nanotube network is very sensitive to the steady shear deformation, and is also to the temperature, which makes the principle of time-temperature superposition be invalid on those percolated PCLCNs. Small addition of nanotube cannot improve the thermal stability of PCL but can increase crystallization temperature remarkably due to the nucleating effect. As the nanotube is much enough to be percolated, however, the impeding effect becomes the dominant role on the crystallization, and the thermal stability increases to some extent. (c) 2007 Wiley Periodicals, Inc.