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Title: The synthesis, structure and properties of polypropylene nanocomposites
Authors: Moodley, Vishnu Kribagaran 
Keywords: Materials;Composite materials;Polypropylene;Thermoplastics;Nanoparticles;Nanotechnology;Nanostructures
Issue Date: 2007
Polymer nanocomposites may be defined as structures that are formed by infusing
layered-silicate clay into a thermosetting orthermoplastic polymer matrix. The
nanocomposites are normally particle-filled polymers for which at least one dimension of
the dispersed particles is in nanoscale. These clay-polymer nanocomposites have thus
attracted great interest in industry and academia due to their exhibition of remarkable enhancements in material properties when compared to the virgin polymer or conventional micro and macro-composites.
The present work describes the synthesis, mechanical properties and morphology of
nano-phased polypropylene structures. The structures were manufactured by melt-
blending low weight percentages of montmorillonite (MMT) nanoclays (0.5, 1, 2, 3, 5 wt. %) and polypropylene (PP) thermoplastic. Both virgin and infused polypropylene structures were then subjected to quasi-static tensile tests, flexural tests, micro-hardness tests, impact testing, compression testing, fracture toughness analysis, dynamic mechanical analysis, tribological testing. Scanning electron microscopy studies were then conducted to analyse the fracture surfaces of pristine PP and PP nanocomposite. X-ray diffraction studies were performed on closite 15A clay and polypropylene composites containing 0.5, 1, 2, 3 and 5 wt. % closite 15A nanoclay to confirm the formation of nanocomposites on the addition of organo clays. Transmission electron miscopy studies were then performed on the PP nanocomposites to determine the formation of intercalated, exfoliated or agglomerated nanoclay structures.

Analysis of test data show that the mechanical properties increase with an increase in nanoclay loading up to a threshold of 2 wt. %, thereafter the material properties degrade.
At low weight nanoclay loadings the enhancement of properties is attributed to the lower percolation points created by the high aspect ratio nanoclays. The increase in properties may also be attributed to the formation of intercalated and exfoliated nanocomposite structures formed at these loadings of clay. At higher weight loading, degradation in mechanical properties may be attributed to the formation of agglomerated clay tactoids.
Results of XRD, transmission electron microscopy studies and scanning electron
microscopy studies of the fractured surface of tensile specimens verify these hypotheses.
Submitted in fulfilment of Masters in Technology: Mechanical Engineering, Durban University of Technology, Durban, South Africa, 2007.
Appears in Collections:Theses and dissertations (Engineering and Built Environment)

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