Effect of Coupling Agent on the Dispersion of PETG Montmorillonite Nanocomposite films

Abstract

Polyethylene terephthalate glycol (PETG) is a clear amorphous polymer, which is extensively used in flexible packaging. The dual packaging requirements of recyclability and long-term shelf life are often difficult to achieve. Meeting these needs become more urgent when considering food packaging for large volumes of soldiers positioned in different parts of the world. Our approach is to develop a high barrier PET packaging system via the Montmorillonite layered silicate (MLS) based nano technology. Prior research has indicated the significant impact of the polymer crystalline regions on the properties of the resultant nanocomposite. Therefore we must first investigate the amorphous PETG. We must also investigate the influence of increased matrix polarity on dispersion of the PETG by incorporating maleic anhydride (MA) onto the PETG backbone. The influence of the clay concentration and maleation are independently investigated. The glass transition of the as-processed and annealed samples are analyzed using Differential Scanning Calorimetry (DSC) while the thermal stability is determined using Thermogravimetric Analysis (TGA). Testing showed a slight depression in the glass transition temperature of PETG film when the MLS is introduced into the system. The nanocomposite films also demonstrated a lower thermal stability in relation to the neat PETG films. The barrier properties were determined on an in-house built calibration unit based on atomic mobility under high vacuum. X-ray diffraction and TEM were utilized to determine the dispersion of the MLS in PETG. The results indicate that the dispersion was concentration independent but maleation of the PETG led to a slight decrease in agglomeration. An increased ultimate tensile strength and modulus was observed in PETG nanocomposites. The barrier properties were improved by incorporating the MLS into the system. Maleation of the PETG resulted in significant yellowing of the nanocomposites.