Читать книгу Polymer Nanocomposite Materials - Группа авторов - Страница 19

In the synthesis of PNCs, it is necessary to uniformly distribute the fillers into matrix in order to realize the functions of fillers. However, due to the fact that the fillers are nanoscale, the uniform dispersion is much different from that of the microscale fillers, which is mainly manifested in the following aspects. First, if the filling operation is carried out according to the volume fraction, much more nanometer fillers than the microfillers are required at the same volume fraction. Therefore, the nanoparticles in matrix are very crowded with greater van der Waals and electrostatic interactions between the particles, making it difficult to distribute evenly. Second, the anisotropic nanofillers have a very high aspect ratio, which makes them more prone to agglomerate. For example, monolayer graphene has aspect ratio of about 10⁴, so they tend to reduce their surface energy by π–π stacking. Third, a large amount of nanofillers with huge surface area is loaded in the polymer matrix, which will produce a large interface area and change the overall performances of the PNC. Therefore, the decisive step in the synthesis of PNCs is the uniform dispersion of nanofillers in polymer matrix. As shown in Table 1.2, the common methods to disperse nanofillers and prevent the aggregation of nanoparticles by using external energy are summarized.

Table 1.2 Summary of common methods for synthesis of polymer nanocomposites.