Three-Dimensional Structure of the Zone-Drawn Film of the Nylon-6/Layered Silicate Nanocomposites

Abstract

Semicrystalline polymer/layered silicate nanocomposites exhibit a unique three-dimensional structure associated with the high-aspect ratio constituents (layered silicates and polymer crystallites), which is sensitive to shear and deformation history. Beginning from quenched biaxially extruded films of nylon-6/ montmorillonite nanocomposites, the impact of elevated temperature uniaxial drawing on the orientation of the layered silicate and crystallites, crystalline polymorphism, and layered silicate buckling was studied using X-ray and transmission electron microcopy. The quenched biaxially protruded films exhibited a uniplanar crystalline texture with the b-axis of the dominate γ-form oriented toward the normal to the film surface and the surface of the layered silicate oriented parallel to the film surface. Small-angle scattering features suggest that the lamellar of the γ-form is within the proximity of the layered silicate and has a fringed micelle structure. Upon uniaxial drawing, α-crystallites developed with a lamellar regularity of ∼15 nm along the draw direction, comparable to previous studies on pure nylon-6 fibers. The newly formed α-form exhibited a uniaxial texture with the b-axis parallel to the draw direction. This suggests that the α-form crystallized during the drawing of the film and does not have an orientation correlation with the layered silicate. Finally, the layered silicate within the zone-drawn film buckled perpendicular to the draw direction, analogous to failure of a uniaxially strained sheet of paper. The failure mode appears to occur for a collection of parallel aluminosilicate layers (2−4) and not individually. Recognition of the structural changes of the layered silicate and crystalline regions in response to uniaxial deformation of planar oriented films is critical to ascertaining the local transport properties of shaped layered silicate nanocomposite parts.