Simultaneous Dielectric Spectroscopy and X-ray Diffraction of Poly(ethylene therephthalate) and PET/Carbon Nanotube Nanocomposites

The crystallization of poly(ethylene terephthalate) (PET) and a nanocomposite of PET with multi-walled carbon nanotubes (MWCNTs) were studied by simultaneous wide and small angle X-ray diffraction and dielectric relaxation spectroscopy. Our purpose is to determine whether the MWCNTs affect the cold crystallization kinetics or phase structure of the PET host. The nanocomposites contained 2{\%} MWCNT by weight, and were prepared by solution mixing, and then compression molding into film. Dielectric measurements were made at frequencies from 100 Hz to 1 MHz, in parallel plate geometry. Measurements of the samples during cold crystallization (Tc$\sim $100-120\r{ }C) were used to investigate the relationship between the growth of crystals and the restriction of the molecular mobility of the amorphous phase. In agreement with previous work, results indicate that a heterogeneous distribution of amorphous regions exists, implying both interlamellar and interfibrillar/interspherulitic placement of the amorphous chains. Addition of carbon nanotubes to the PET increased the rate of cold crystallization, but did not affect the glass transition relaxation process.