TIT# Studying Nanostructure Gradients in Injection-Molded PP/MMT Composites by Microbeam SAXS AUT# Stribeck, Norbert; Schneider, Konrad; Zeinolebadi, Ahmad; Li, Xuke; Sanporean, Catalina-Gabriela; Vuluga, Zina; Iancu, Stela; Duldner, Monica; Santoro, Gonzalo; Roth, Stephan V.; SOU# Sci. Tech. Adv. Mater. (2014), 15, 015004 LOC# xv145 CLA# COM# doi:10.1088/1468-6996/15/1/015004 APP# MAT# ABS# The core-shell structure in oriented cylindrical rods of polypropylene (PP) and nanocomposites (NC) from PP and montmorillonite (MMT) is studied by microbeam smallangle X-ray scattering (SAXS). The structure of neat PP is almost homogeneous across the rod showing regular semicrystalline stacks. In the NCs the discrete SAXS of arranged crystalline PP domains is limited to a skin zone of 300 ?m thickness. Even there only frozen-in primary lamellae are detected. The core of the nanocomposites is dominated by diffuse scattering from crystalline domains placed at random. The SAXS of the MMT flakes exhibits a complex skin-core gradient. Both the direction of the symmetry axis and the apparent perfection of flake-orientation are varying. Thus there is no local fiber symmetry, and the structure gradient cannot be reconstructed from a scan across the full rod. To overcome the problem the rods are milled. Scans across the remnant ligaments are performed. For the first time ligaments have been carved out in two principal directions. Comparison of the corresponding two sets of SAXS patterns demonstrates the complexity of the MMT orientation. Close to the surface (< 1 mm) the flakes cling to the wall. The variation of the orientation distribution widths indicates the presence of both MMT flakes and grains. The grains have not been oriented in the flowing melt. An empirical equation is presented which describes the variation from skin to core of one component of the inclination angle of flake-shaped phyllosilicate filler particles.