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 300 μm 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.

Variation of poly(vinylidene fluoride) morphology due to radial cold flow in a flexible pipe

“…These blind areas have partly been filled exploiting the four‐quadrant symmetry of SAXS patterns with fiber symmetry. Data for the remaining “cheese holes” have been extrapolated assuming that SAXS patterns do not show sharp reflections which might hide in such a hole .…”

Shape Memory Polymer–Inorganic Hybrid Nanocomposites

“…In 2014, Stribeck et al observed the properties of injection-molded polypropylene (PP)/MMT composites by microbeam small-angle X-ray scattering [97]. They were interested in studying gradient effects along the radius of injection-molded nanocomposite rods.…”

“…These approaches hold tremendous promise for understanding morphological phenomena in SMPINCs. Reprinted from Stribeck et al [97], Copyright 2014, Open Access Fig. 7).…”

Polypropylene/silica micro‐ and nanocomposites modified with poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene)

“…19 Mae et al have observed that the elastic modulus and the strain values of iPP/SiO 2 composites modified with poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) have depended on the selectivity of SiO 2 nanoparticles, i.e. 25 Although SEBS elastomer was widely applied as a compatibilizer for polymer blend systems, its application as impact modifier and compatibilizer in polypropylene composites has been reported in only recently published papers of Panaitescu et al and Stribeck et al 21,22,26 Elastomers with encapsulation ability have been added to composites as compatibilizing agents in small amount (up to 5%) like other compatibilizers. 20 The most recent investigations of the iPP/SiO 2 / SEBS composites with PP-g-MAH added as compatibilizer by Panaitescu et al confirmed relatively good compatibility of the iPP/SEBS interface resulting in improvement of mechanical and dielectrical properties.…”

“…are they inside or outside of dispersed elastomeric SEBS particles. 21,26 Accordingly, El-Midany and Ibrahim introduced in polypropylene filled with 3% white microsilica sand as mineral filler 2.5% and 5% of SEBS and SEBS-g-MAH. 21,22 The location of filler and interactions played again the crucial role in determing the propereties of such composite systems.…”