Preparation of Silicate Layer Polymer Nanocomposites

The ultimate microstructure formed, critically depends on a number of factors, including  

A more extensive account of the formation, structural characterisation and physical properties of silicate layer nanocompsites can be found in Chapter 10. The discussion below focuses on nanocomposite preparation by melt processing, since this provides the most promising route for more widespread acceptance and subseqnent commercial exploitation of these materials. 

However, this task becomes more challenging with polyolefins, and it is generally necessary to have some polar functionality present, most commonly by inclusion of MA grafted polymer in the composition (typically at a 5% polymer addition level) [114], Aco-rotating twin-screw extruder is frequently recommended for this purpose, however the form of screw profile used and feed location of the components, can influence the structure and properties of compounds produced [115]. For example, it was reported that combined dosing of polymer and filler at the feed end of the extruder gave better intercalation than downstream addition of the clay. 

Reactive extrusion provides an alternative approach to melt compounding, for the preparation of polyamide-6 nanocomposites [117]. In this study, a co-rotating twin-screw extruder was used to anionically polymerise e-caprolactam in the presence of organically modified montmorillonite clay. Hence, intercalcation and delamination occur concurrently with polymer formation. 

To assist in the production of silicate layer nanocomposites SCCO2 has also been used. Intercalcated poly(methyl methacrylate) clay nanocomposites, containing 25-50% by weight of clay, have been made by polymerisation of methyl methacrylate in a SCCO2 pressure vessel [112]. This overcame previous melt processing difficulties caused by the 

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