The formation processes of epoxy nanocomposites with carbon (nanotubes, graphene, and graphite), metal-containing, and aluminosilicate (montmorillonite and halloysite tubes) fillers are considered. A high reactivity of epoxy groups and a thermodynamic miscibility of epoxy oligomers with many substances make it possible to use diverse curing agents and to accomplish curing reactions under various technological conditions. Epoxy nanocomposites are designed to realize to the same extent the unique functional properties of nanoparticles: electric, magnetic, optical, chemical, and biological. The mutual effect of both a matrix and nanoparticles on the composite formation is discussed.
TopIntroduction
Since around the mid-1990s, polymer nanocomposites have become the subject of considerable attention, as evidenced by monographs, and a great number of reviews: since 2010, more than two dozen papers have been published (Irzhak, 2017). The application of nanocomposites is associated with their unique properties related to a huge specific surface and high surface energy of nanoparticles. Nanosized particles, as opposed to microinclusions and coarser inclusions, are not stress concentrators, and this circumstance facilitates a marked improvement in the mechanical properties of nanocomposites. Compared with the respective polymers, the transparency of nanocomposites does not decrease, because nanoparticles do not scatter light because of their small sizes. Depending on the type of nanoparticles introduced in polymeric materials even at a low concentration, nanocomposites acquire remarkable chemical (primarily catalytic), electrophysical, and biomedical properties, thereby opening wide potential for their use.
Among polymer nanocomposites (Figure 1, curve 1), it would appear that composites based on an epoxy matrix occupy an insignificant place—nearly 10% as to the number of publications—but an ever increasing number of papers appear annually (curve 2). Moreover, the interest in them grows almost exponentially, as evidenced by the number of citations (curve 3).
Figure 1.
The number of publications on (1) polymeric and (2) epoxy nanocomposites and (3) the number of their citations according to the Web of Science Reprinted with permission from IAPC “Nauka” (2017, Irzhak)
Epoxy polymers in terms of a set of properties stand out among other polymeric materials and play an important role in aerospace, automotive, shipbuilding, and other industries. Their wide application in engineering is associated, firstly, with a high processability of epoxy resins and, secondly, with the unique combination of performance characteristics of their curing products (Paquin, 1958, Lee, 1967, Chernin, 1982, Khozin, 2004).
A high reactivity of epoxy groups and a thermodynamic miscibility of epoxy oligomers with many substances make it possible to use diverse curing agents and to accomplish curing reactions under various technological conditions (Irzhak, 1979, Rozenberg, 1986, Okabe, 2013). Of no small importance are the features of synthesis processes, such as the absence of volatile products and low level of shrinkage.
Epoxy polymers have high values of static and shock strength, hardness, and wear resistance. They possess marked thermal stability and heat resistance. Many solid surfaces form strong adhesive bonds with epoxy polymers (Paquin, 1958, Lee, 1967). This circumstance determines their use as compounds, glues, paint and lacquer materials, and coatings, including in aerospace engineering. Epoxy nanocomposites are designed to realize the unique functional properties of nanoparticles: electric, magnetic, optical, chemical, and biological.