Platelets alignement

The long-term goal of this investigation is an understanding of the effect of a particular mode of adsorption on montmorillonite which ensures that under pressure the clay platelets align parallel to a solid surface even under saline conditions. This is an important phenomenon in petroleum recovery processes. 

The application of this technique to talc-reinforced polypropylene has shown that the microstructure of platelets and the resulting physical properties of the moulded composites are markedly affected [171)]. With two live feeds located at either end of the mould cavity, the talc platelets exhibited strong talc platelet alignment throughout the thickness of the moulding in the direction of the ap-... 

The above technique can be advantageously adapted to a situation where the polymer of interest is not soluble in any solvent, as is the case for polyimides. The polyimide precursor, ie, a poly(amic acid) solution in dimethylacetamide, is prepared and blended to a dispersion of an organomodified montmorillonite in the same solvent. Dimethylacetamide is then gradually removed, and upon heating the poly(amic acid) film at 300°C imder nitrogen atmosphere the polyimide-clay hybrid is obtained. When an ammonium salt of dodecylamine is used in the ion-exchange process, true exfoliation is achieved and fiirthermore the clay platelets align parallel to the film surface (28). 

Fignre 15.12. Enhaucement in stiffiiess vs. the ai-ea platelet fiUing fraction, for both randomly aligned platelets, and platelets aligned with the af-direction. The platelets were straight and had a fixed aspect ratio (length/width) of 100 1... 

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