Research Information System
Other, pp.245-246, 2012
Poly(ethylene terephthalate) (PET) has been considered as a commodity polymer because of the diversity of its applications, as in packaging, fiber production, and molded goods. In literature, there have been plenty of studies related to the preparation of PET/clay nanocomposites by in-situ polymerization and melt compounding. The extrusion method played very important role in preparing PET/clay nanocomposites due to its simple and versatile processing way. On the other hand, this method can potentially cause thermal decomposition of commonly used alkyl ammonium ions in modified clays, which caused further degradation of polymer matrix. In recent years, a method called “thermokinetic mixing” has begun to be employed for preparing polymer nanocomposites. The thermokinetic mixing system, which requires no external heating, is specifically designed to handle difficult compounding and dispersion applications within a few minutes. Thanks to short processing times and high shear rates, it would be quite interesting to prepare PET/organoclay nanocomposites on the thermokinetic mixer.
The scope of this work consists in studying the thermal decomposition behavior of the poly(ethylene terephthalate) (PET) and its nanocomposites generated with organically modified clays using different processing methods. To achieve this goal, an intercalating agent was synthesized and montmorillonite type clay modified with this intercalating agent was mixed with the PET by employing melt extrusion and high shear mixing method. We then compared the nanocomposites in terms of dispersion properties using X-ray Diffraction (XRD) and Scanning Electron Microcscope (SEM). The thermal stability of the organoclays and nanocomposite materials was evaluated by Thermogravimetric Analysis (TGA) and dilute solution viscosity technique, respectively.
Our results showed that changing the processing type from extruder to thermokinetic mixer reduced the clay particle size substantially. Processing on the thermokinetic mixer obviously disperses the clay particles in the PET matrix phase better than the extrusion process. The results from the SEM analyses are in excellent agreement with those obtained from the investigation of XRD data. Larger shear rates induced during thermokinetic mixing process were revealed to be responsible for a better dispersion of the clay mineral. The results show that manganese in the raw clay –though chemically bound- leads to decreased IV values, i.e. decreased molecular weight in PET/organoclay nanocomposites. Accordingly, content of raw clay type, especially manganese level should also be considered when working with PET. It was revealed that working on the thermokinetic mixer provided substantial contributions such as shorter processing times in comparison to the melt extrusion method, elimination of drying step before melt processing, which has been accepted as an inevitable process for PET so far, less thermal degradation because of short processing times, and more homogeneous and better dispersion of the clay particles in PET matrix phase.