Rheology of multi-walled carbon nanotube/poly(butylene terephthalate) composites

Multi-walled carbon nanotube/Poly(butylene terephthalate) nanocomposites (PCTs) were prepared by melt compounding. The microstructure of PCTs was investigated using transmission electron micrographs and Fourier transform infrared spectrometer. The linear and nonlinear as well as transient rheological properties of PCTs were characterized by the parallel plate rheometer. The results reveal that the surface modification can improve the dispersion state of nanotube in matrix. PCTs present a low percolation threshold of about 1-2 wt % in contrast to that of Poly(butylene terephthalate)/clay nanocomposites. The network structure is very sensitive to both the quiescent and large amplitude oscillatory shear deformation, and is also to the temperature, which makes the principle of time-temperature superposition (TTS) be valid on PCTs only in a very restricted temperature range. The stress overshoots to the reverse flow are strongly dependent on both the rest time and shear rate but show a strain-scaling response to the startup of steady shear, indicating that the broken network can reorganize even under quiescent condition. The nanotube may experience the long-range, more or less order during annealing process. (c) 2007 Wiley Periodicals, Inc.