Morphology of Injection-Molded Isotactic Polypropylene/Silica Composites Prepared via in-Situ Sol−Gel Technology

Abstract

We report on the semicrystalline morphology of injection-molded isotactic polypropylene (iPP)/silica composites prepared via in situ sol−gel technology using hyperbranched polyethoxysiloxane as a silica precursor. The microstructural analysis has been carried out with a combination of small- and wide-angle X-ray scattering and 1H solid-state NMR spectroscopy. The in situ formed silica particles significantly alter the semicrystalline morphology of iPP by improving orientation of the “mother” crystals in the sample core simultaneously with an increase of the “daughter” crystal fraction. Moreover the particles induce formation of thicker crystalline domains and growth of β-crystals in the sample core. The observed morphological modifications can be accounted for by a 2-fold effect of the silica particles, i.e., their action as a nucleating agent of the β-phase, on the one hand, and as a lubrificant reducing the polymer melt viscosity, on the other. Proton spin-diffusion experiment using a double-quantum filter was found suitable for the measurement of the chain mobility gradient in the interface region. The results obtained indicate enhanced polymer chain mobility in the amorphous region in the presence of the silica particles. Finally, the morphology and chain dynamics of the iPP/silica composites are correlated to mechanical properties of the injection-molded samples.

Correlation of nanostructural parameters and macromechanical behaviour of hyperbranched‐modified polypropylene using time‐resolved small‐angle X‐ray scattering measurements

“…The presence of lamellae oriented in the direction parallel to s 3 is deduced from the set of strong vertical streaks and from the corresponding modulation in the equatorial band of the CDF. The finding of two sets of lamellae that are oriented perpendicular to each other is compatible with a well‐known peculiar architecture of PP nanostructure that is known as a mother–daughter crystal lamellar structure, also called a crosshatching structure . Utilizing these notions, it is possible to trace the nanostructural changes that occur as a consequence of the modification process both qualitatively and quantitatively.…”

Recent Applications of Ionic Liquids in the Sol-Gel Process for Polymer–Silica Nanocomposites with Ionic Interfaces

“…The Wilkes morphological model described the O-I polymer as a hybrid network consisting of flexible polymer-rich domains with dispersed glassy silica-rich domains and a mixed interface. Since then, many in situ formed polymer-silica nanocomposites based on polypropylene (PP) [113][114][115], polyvinyl acetate (PVA) [116], polyvinyl alcohol (PVOH) [117][118][119], high amorphous vinyl alcohol (HAVOH) [11], polymethyl methacrylate (PMMA) [120], polydimethylsiloxane (PDMS) [121,122], polyacrilate [123,124] and epoxy matrix [4,7,112], were successfully synthesized.…”

Synthesis, molecular characterization, evaluation of polymorphic behavior and indentation response in isotactic poly(propylene-co-1-heptene) copolymers

“…Incorporation of specific fillers or other polymers can allow spreading out even more its application fields. This addition can be performed either by direct blending of the different components, filled polypropylenes [1][2][3][4][5][6] or blends [7,8], or by polymerization in the presence of fillers [9][10][11].…”