Nanocomposite with oriented properties

Table 3. Mechanical Properties of Track-Etched Membranes and Nanocomposites with Oriented Polyelectrolyte Nanodomains...

Around 1900, widely forgotten reports indicated the preparation of polymer nanocomposites with uniaxially oriented inorganic particles, and their remarkable optical properties (14,15). Dichroic plants and animal fibrils (eg, linen, cotton, spruce, or chitin, amongst others) were prepared by impregnation with solutions of silver nitrate, silver acetate, or gold chloride, followed by reduction of the corresponding metal ions under the action of light (16). 

Effective medium theory (EMT) is commonly used to describe the microstructure-property relationships in heterogeneous materials and predict the effective physical properties. It has recently been revised to predict the thermal conduction of nanocomposites. For nanocomposites with nanopartides on the order of or smaller than the phonon mean free path, the interface density of nanopartides is a primary factor in determining the thermal conductivity. In graphite nanosheet polymer composites, the interfacial thermal resistance still plays a role in the overall thermal transport. However, the thermal conductivity depends strongly on the aspect ratio and on the orientation of graphite nanosheets. 

Incorporation of silicate nanolayers in semi-crystalline polymers like polypropylene ean have a two-fold effect on the barrier properties, (1) well oriented large aspeet ratio platelets will increase the tortuosity of the diffusion path and (2) the nanolayers will affect the crystalline order (size and interlamellar spacing) and possibly affect the barrier properties. The extent of orientation is greater in blown film than in extmsion cast film and this leads to similar trends in barrier properties of polypropylene nanocomposites with 7wt.% 1.3 IPS (silated) clay as reported by Qian et al. With cast films, the nanoeomposite had a lower permeability to oxygen by a faetor of 1.5 compared to neat polypropylene. With blown films, the nanocomposite permeability to oxygen was lower by a factor of 2.5 compared to neat polypropylene. However, Ellis and D Angelo were able to prepare only intercalated polypropylene nanocomposites with the same 1.31 PS and obtained no improvement in permeability to a solvent over that for neat polypropylene. This underlines the greater sensitivity of barrier performanee to the level of dispersion and orientation. 

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