Alignment Control of Clay and Its Effect on Properties of Polymer Nanocomposites

Polymer nanocomposites are well known to show high performances by the addition of a small amount of nanofiller. However, the brittleness has often been reported as a general issue of the nanocomposites. In this study, we revealed the excellent toughening effect of poly (vinyl alcohol) (PVA)/montmorillonite (MMT) nanocomposites by controlling the alignment of MMT by drawing. The PVA/MMT nanocomposites with 5 wt% MMT loading was prepared and then drawn by uniaxial drawing, roll drawing and simultaneous-biaxial drawing. The drawn nanocomposites, where MMT was highly aligned parallel to the film surface, showed excellent enhancement in the mechanical properties and barrier properties. It is noteworthy that not only the Young's modulus and the tensile strength, but also the elongation at break and the toughness remarkably increased for the drawn nanocomposites. For example, the simultaneously-biaxially-drawn nanocomposite showed the toughness of 17 times higher than that of the as-cast nanocomposite. Furthermore, the swelling ratio was comparable to that of surface fluorinated PVA film.