Thermodynamics of polymer-clay interactions

10 Edge treatment with silane coupling agents 

The last method of surface treatment is the use of coupling agents. Unfortunately for montmorillonite, the majority of reactive hydroxides are at the edges of the clay plates. In normal commercially available montmorillonite, these edges account for only about 2% of the total surface area and therefore would not be expected to contribute greatly to the ultimate engineering properties of the composite. This point of view overlooks the fact that the edges are the first part of a clay tactoid that a polymer encounters and therefore can act as a barrier to polymer intercalation, since most polymers do not associate well with hydroxides. 

There have been a number of reports where substantial improvement in the nanocomposite physical properties have been demonstrated by using the proper silane coupling agent [13,14,15], In one of these cases, polypropylene (PP) was shown not to intercalate at all without silane coupling of the edges. 

---