Hybrid Composite Materials

April 18, 2017

Hybrid materials are a type of composite in which two components interact at the nanostructure or molecular level. They are used today in such varied applications as corrosion protection, various scratch-resistant and decorative coatings, and dental fillers.

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For dental applications, the benefits of a hybrid composite include: reduced polymerization shrinkage, packability, esthetics of a ceramic in a composite, non-sticky consistency for easy sculpting, excellent polishability, high bond strength and radiopacity.

Hybrid materials are a type of composite in which two components interact at the nanostructure or molecular level. These differ from traditional composites, where the two component materials interact at the micrometer to millimeter level. Because the materials mix at such small length scales, the bulk hybrid material that results is more homogenous and can show properties either between those of the original material or entirely new. Most often one component is organic and the other is inorganic.

Hybrid materials are classified according to the interactions that are possible between the organic and inorganic species present in the material. Class I materials exhibit weak (van der Waals, hydrogen bonding, or weak electrostatic) interactions between the two components. On the other hand, Class II materials show strong chemical (i.e., covalent bonding) interactions between the two components.

While it may be easy to think of hybrid materials as nanocomposites, that would be a mistake. The term nanocomposite is used to describe a combination of organic and inorganic structural units which yield a material with composite properties. The properties of each component material are present in the final composite and do not change after mixing. Alternatively, hybrid materials are formed if the mixing of organic and inorganic structural units results in the appearance of new physical properties not held by either original component.

Hybrid materials are synthesized through either the building block approach or in situ formation of the components. In the building block mechanism, the building blocks at least partially keep their integrity at the molecular level, meaning that structural units in the source materials are also present in the final material. This causes the properties of the building blocks to usually survive formation of the matrix. On the other hand, in situ formation requires a chemical transformation of the precursor materials. Typically this mechanism is used if organic polymers are formed in the material creation process, but can also be used if a sol-gel process is used to produce the inorganic component. Because the precursor materials are chemically transformed, this creation mechanism generally leads to new properties in the final material.

Hybrid materials have many significant advantages over conventional composites. For example, inorganic materials with desired optical, electronic, or magnetic properties can be incorporated into relatively low-cost organic polymer matrices. Also, with materials engineered on the nanoscale light scattering can be eliminated, resulting in optical transparency of the hybrid material. Finally, hybrid materials can be processed similar to polymers, at a much lower temperature because of either their large organic content or because small molecular precursors can form crosslinked inorganic networks (following the same mechanism as polymerization reactions).

Hybrid materials are used today in such varied applications as corrosion protection, various scratch-resistant and decorative coatings, dental fillers (see above), and much more. Considering their superiority in many respects to more traditional composites, it is reasonable to expect their use to grow in the future as manufacturing volume grows and the materials become less expensive.

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