Crystallization Kinetics of Ethylene Vinyl Acetate with Modified Clay Nanocomposites

Abstract

The interaction of nanoclays with polar polymers is receiving greater interest because the nanoclay significantly improves the thermal stability of the composites; however, since most polar polymers are bio-based, their mechanical properties and processing are of relatively lower standard than the oil-based polymers. We investigated a commercially relevant polymer with varying degree of polarity (poly(ethylene vinyl acetate) copolymer (EVA) with varying polarity due to varying vinyl acetate content (9, 18 and 28%)) and its interaction with organo-modified nanoclay filler (CloisiteR C15A and C30B). Specifically, we studied the crystallization kinetics and the relative dispersion of the nanoclays within the composites using modulated differential scanning calorimetry (DSC) and X-ray Diffraction techniques. Transmission Electron Microscopy results show that clay platelets have increasing tendency to be dispersed as the polarity of the matrix is increased; however, the overall matrix crystallinity remains largely unmodified due to nanoclays but the overall morphology was significantly modified in a way that there was an increase in the ‘rigid-amorphous’ phase. Using Avrami kinetics, we demonstrate that nanoclays play a significant role in the mechanism of growth of crystals and crystalline distribution for EVA polymer and the analysis could be used to compare processing of composites for optimizing mechanical properties for a range of applications in the flexible packaging industry.