Bicontinuous nanocomposites

There are generally two approaches used for the production of bicontinuous nanocomposites. 

Figure 24.2 Nanostructure of bicontinuous nanocomposites. Top Pictorial description of interconnected organic and inorganic domains with gradient density interphase. Bottom TEM micrograph of an epoxy/silica bicontinuous nanocomposite.

Other oligomers that have also been used for this purpose are polytetramethylene oxide and polycaprolactones, both containing alkoxysUane functional groups at the chain ends [1,10,11], More recently the organic oligomers that have been used for the production of bicontinuous nanocomposites are commerdal thermosetting resins, particularly epoxy resins. 

The types of reactions involved in the production of sUica-based bicontinuous nanocomposites are as follows ... 

Since the maximum stress that a material will withstand is synonymous with its strength, that is, the value of the stress at which fracture occurs, it can be stipulated that due to the isostrain conditions within the two phases, fracture in bicontinuous nanocomposites takes place when the most brittle phase, in this case the inorganic phase, reaches its ultimate strain value, E g.acture- When this condition is reached, fracture will rapidly propagate through the organic phase without any further increase in strain. Expressed in terms of fracture conditions Eq. (24.1), therefore, becomes... 

Epoxy resins are widely used in coatings in applications requiring high resistance to abrasion and chemical resistance. Different types of resin and hardener combinations are used to tailor the properties to specific end uses. The increasingly more stringent requirements in many applications makes the enhancement of properties by the production of bicontinuous nanocomposites described previously a viable route for further developments in epoxy resin coatings. 

Potential Applications of Bicontinuous Nanocomposites 477 Epoxy Resin... 

Figure 24.6 Comparison of room-temperature TH F absorption as a function ofimmersion timeof an epoxy resin control with epoxy/silica particulate nanocomposite and epoxy/silica hybrid (bicontinuous nanocomposite).

Figure 24.7 Comparison of effects of phase bicontinuity on nanocomposites. Nanocomposite particulate nanocomposite. Hybrid Bicontinuous nanocomposite (without molybdate dopant).

Figure 24.8 Effects of type of molybdate dopant on the dynamic mechanical properties of epoxy/ silica bicontinuous nanocomposites.

Figure 24.9 Effect of molybdate dopant on the solvent (THE) absorption characteristics of bicontinuous nanocomposites.

Polyimides are probably the most appropriate dass of polymers for the production of bicontinuous nanocomposites, in so far as they represent types of polymers that have been widely used in applications requiring stringent performance at high temperatures. The incorporation of continuous silica domains, therefore, is expected to enhance the high-temperature properties to bridge the gap between polymers and... 

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