title: Studying nanostructure gradients in injection-molded polypropylene/montmorillonite composites by microbeam small-angle x-ray scattering.
abstract: The core-shell structure in oriented cylindrical rods of polypropylene (PP) and nanoclay composites (NCs) from PP and montmorillonite (MMT) is studied by microbeam small-angle 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 300μm thickness. Even there only frozen-in primary lamellae are detected. The core of the NCs 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 machined. Scans across the residual webs are performed. For the first time webs 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.
authors.affiliation: Department of Chemistry, Institute TMC, University of Hamburg, Bundesstrasse 45, D-20146, Hamburg, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Stribeck
authors.affiliation: Leibniz-Institut für Polymerforschung (IPF), D-01069, Dresden, Germany.
authors.forename: Konrad
authors.initials: K
authors.lastname: Schneider
authors.affiliation: Polymer Consult Ltd, Dorfgrund 6, D-22397, Hamburg, Germany.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Zeinolebadi
authors.affiliation: Department of Chemistry, Institute TMC, University of Hamburg, Bundesstrasse 45, D-20146, Hamburg, Germany.
authors.forename: Xuke
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Mechanical and Manufacturing Engineering, Aalborg University, Fibigerstræde 16, DK-9220, Aalborg, Denmark.
authors.forename: Catalina-Gabriela
authors.initials: CG
authors.lastname: Sanporean
authors.affiliation: National Research and Development Institute of Chemistry and Petrochemistry ICECHIM, Splaiul Independentei 202, Bucharest, Romania.
authors.forename: Zina
authors.initials: Z
authors.lastname: Vuluga
authors.affiliation: National Research and Development Institute of Chemistry and Petrochemistry ICECHIM, Splaiul Independentei 202, Bucharest, Romania.
authors.forename: Stela
authors.initials: S
authors.lastname: Iancu
authors.affiliation: National Research and Development Institute of Chemistry and Petrochemistry ICECHIM, Splaiul Independentei 202, Bucharest, Romania.
authors.forename: Monica
authors.initials: M
authors.lastname: Duldner
authors.affiliation: HASYLAB at DESY, Notkestraße 85, D-22603, Hamburg, Germany.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Santoro
authors.affiliation: HASYLAB at DESY, Notkestraße 85, D-22603, Hamburg, Germany.
authors.forename: Stephan V
authors.initials: SV
authors.lastname: Roth
keywords: Injection-molded; Layered silicate; Orientation; Polypropylene; Skin–core; X-ray scattering