Morphological influence on mechanical characterization of ethylene-vinyl acetate copolymer–clay nanocomposites

Ethylene-vinyl acetate copolymer (EVA)/montmorillonite (MMT) clay nanocomposites with varying degree of intercalation and exfoliation have been prepared using direct melt blending techniques with various degrees of polarity (9, 18, and 28 wt% vinyl acetate [VA]) and two different types of clay modification. Morphological characterization using wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) have indicated/confirmed the presence of intercalation and/or a combination of intercalation and exfoliation existing in the nanocomposites. The effects of these (simple intercalation or mixed intercalation/exfoliation) states and the effect of changing matrix polarity (by changing VA wt% content) on the nanocomposite mechanical behavior were studied. There is sufficient evidence from the mechanical studies that 1) the presence of nanoclay can simultaneously improve modulus and strength of the nanocomposites, and 2) the mechanical properties are a combined function of the clay concentration and the nanocomposite morphology (due to the VA wt% and presence of clay). It is shown here that interrelation between the VA wt% content and the clay exfoliation affects the mechanical properties in a way that has a positive and increasing slope with increasing loading of clay. It is shown that a clear understanding of the nanocomposite mechanical properties can be obtained from its morphological analysis.

[1]  M. Jollands,et al.  Crystallinity of Polypropylene-Silica Ash Composites Affected by the Mixing Conditions – DSC Studies , 2004 .

[2]  S. Bhattacharya,et al.  Study of the orientation and the degree of exfoliation of nanoparticles in poly(ethylene‐vinyl acetate) nanocomposites , 2003 .

[3]  J. Jog,et al.  Copolyester/layered silicate nanocomposites: The effect of the molecular size and molecular structure of the intercalant on the structure and viscoelastic properties of the nanocomposites , 2003 .

[4]  C. Ha,et al.  Nanostructure of EVA/organoclay nanocomposites: Effects of kinds of organoclays and grafting of maleic anhydride onto EVA , 2003 .

[5]  Jeffrey W. Gilman,et al.  Characterization of Polymer-Layered Silicate (Clay) Nanocomposites by Transmission Electron Microscopy and X-Ray Diffraction: A Comparative Study , 2003 .

[6]  M. Tavares,et al.  High‐resolution solid‐state NMR and SEM study of the interaction behavior of poly(ethylene‐co‐vinyl acetate)/poly(vinyl acetate) blends , 2002 .

[7]  R. Vaia,et al.  X‐ray powder diffraction of polymer/layered silicate nanocomposites: Model and practice , 2002 .

[8]  P. Dubois,et al.  Polymer-layered silicate nanocomposites: preparation, properties and uses of a new class of materials , 2000 .

[9]  M. Tavares,et al.  Solid-state NMR and morphological studies of poly(ethylene-co-vinyl acetate)/poly(vinyl acetate) blends , 1999 .

[10]  M. Tavares,et al.  NMR study of commercial poly(ethylene-co-vinyl acetate) , 1998 .

[11]  M. Tavares,et al.  NMR carbon-13 high resolution study of poly(ethylene-co-vinyl acetate) , 1997 .