Polymer nanocomposites have attracted interest for many years due to their enhanced barrier properties. This has translated into commercial applications from food packaging to fuel storage, and has sparked interest in barrier modeling. While simplifying are often invoked and microstructural changes ignored, the commonly invoked tortuous path models nevertheless show the ability to capture some of the behavior of these materials. More recently, nanolaminates consisting of a majority of highly oriented nanolayers held together by a minority of a polymeric binder have attracted significant attention thanks (among other things) to their extreme barrier properties. Their performance is generally far in excess of what is seen in melt-blended polymer nanocomposites, and inspires significant practical interest. From a scientific standpoint, these materials also offer a clear opportunity to better understand the factors controlling nanocomposite permeation behavior. We report on efforts to develop such an understanding. Polystyrene has been combined with two different nanoclays, one compatible, the other incompatible. Homogeneous, fully dense films based on both nanoclays and containing 0% to 100% polystyrene were prepared via automated spray deposition. Nanolaminate structure was assessed via 2D x-ray diffraction and scanning electron microscopy, with composition and density also confirmed and consistent with expectations. An in-depth investigation of the oxygen permeability of these materials is presented, with emphasis on the effects of composition and intercalation. Common analytical models are applied both as-is and orientation-corrected, and additional results from nanolaminates based on other amorphous polymers are presented as well. The range of applicability of various analytical models is clarified and important parameters controlling barrier properties are identified, with clear implications for polymer nanocomposites in general.

Assessing gas permeability in polymer nanolaminates

249th National Meeting (2015)

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