Polypropylene layered silicate nanocomposites

Even after organic modification of the clays, polypropylene does not wet the surface of clays because it is nonpolar. It is necessary to blend in a functionalized polymer such as maleated polypropylene (PP-g-MA) that wets the modified clay surface more readily and is also miscible with the bulk polymer. Okada and coworkers were the first to produce polypropylene layered silicate nanocomposites by melt compounding the modified elay with PP-g-MA and PP. The progress made since then in preparing and characterizing polypropylene layered silicate nanocomposites is reviewed in this chapter. We discuss advances in formulations, preparation methods and characterization then proceed to effects of the dispersion state (intercalated vs. exfoliated) and of silicate loading on crystallinity, mechanical performance and other properties, and end with a summary of progress to date with these composites. All the results presented in this chapter refer to isotactic polypropylene nanocomposites with layered or smectite clays. 

Fibiger and coworkers from Dow with a proprietary process these high molecular weight compatibilizers lead to composites with much improved mechanical properties. 

1 TGA scan of C-18 clay (Nanocor 1.30 P), showing loss of organic surfactant from interlayer galleries above 200°C. 

Ultrasonication has been used after melt compounding to yield enhanced dispersion in some cases. 

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