Montmorillonite and Organo Clays Nano Composites

Compounds consisting of montmorillonite clay with an organic amine and a polymer are really ternary systems and should be discussed in Section 7.4, where we will consider them in more detail. We will, however, briefly discuss them here. 

As discussed in Sections 1.4.7 and 1.4.12.1, silicate minerals possess galleries between the silicate layers containing electrical charges. Some of the silicate mineral crystals contain MgO or other compounds between the SiOj layers and are impenetrable (as is the case of talc). 

Montmorillonite clay, on the other hand, can absorb indehnite amounts of H2O into these galleries and displace the Si03 layers to distances much greater than the initial 0.001 pm or 1 nm [110]. 

In the 1960s there were studies of absorption of monomers by clays [116, 117]. In more recent years, monomers such as caprolactam were absorbed into organo clays and were subsequently polymerized. The most important of these efforts involved Toyota researchers [118 to 125] using caprolactam. These products were called nanocomposites and seem to contain polyamide intercalated between silicate layers or had exfoliated structures. Other monomers have also been absorbed into montmorillonite and polymerized. These include the formation of polyimides [126], epoxy resins [127], and polylactones [128]. 

Kojima et al. [ 122] report that the polyamide-6/montmorillonite compound (nanocomposite or hybrid) has superior modulus, tensile strength, flexural modulus, and impact strength compared to neat polyamide-6, as well as higher heat distortion temperature. Indeed, with 4.7 wt% montmorillonite, the heat distortion temperature was increased 87 °C over neat polyamide-6 to 152 °C. 

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