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Polymer nanocomposites with layered silicates

Andrzej Galeski 1Ewa Piorkowska 

1. Polish Academy of Sciences, Center of Molecular and Macromolecular Studies (CMMS-PAS), Sienkiewicza 112, Łódź 90-363, Poland


Polymer-layered silicate nanocomposites are a new class of materials with improved properties. For some polymer systems the use of specific compatibilizers is necessary to achieve exfoliation during melt compounding. Another way to enhance exfoliation are so-called "exfoliation promoters" (EP) [Polish Pat Appl]. Organo modified MMT (o-MMT) weakly nucleates crystallization of polypropylene (iPP) nanocomposites in static conditions while in shear very strongly. Mechanical properties improvement of polymer nanocomposites is usually below expectation because MMT platelets are curved when exfoliated and first they straighten before fully loaded. Melt compounding and any processing of MMT nanocomposites causes irreversible orientation of platelets. This is advantageous in film blowing where the orientation of platelets parallel to the film surface increases barrier properties. Prolongation of melt compounding of polylactide (PLA) with o-MMT led to a full exfoliation as revealed by TEM and SAXS. An increase of the dispersion MMT layers improved the thermal stability and barrier properties and HDT and elastic modulus of PLA and decreased its crystallizability. Thermooxidative and thermal stability of iPP nanocomposite with fully exfoliated MMT studied by simultaneous DSC and TGA up to 500oC permitted to identify precisely the specific mechanisms of polymer degradation. Simultaneous DSC and TGA demonstrated that alkylammonium modified clay exhibited a strong stabilizing effect on iPP in oxygen-free atmosphere. In all systems a fraction of o-MMT is resistant to exfoliation and to wetting by hydrophobic polymers. Those particles contain quartz and should be removed by thorough filtering.


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Related papers

Presentation: Invited oral at E-MRS Fall Meeting 2006, Symposium D, by Andrzej Galeski
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-23 16:32
Revised:   2009-06-07 00:44