Exfoliation of Graphite and PP/Graphite Nanocomposites Prepared through Pan-milling
Qi Wang, Kanshe Li
State Key Lab of Polymer Materials Engineering of China
China
Keywords: exfoliation, PP/graphite nanocomposites, electrical conductivity
Polymer/layered inorganic compound nanocomposite is of increasing interest due to its good barrier properties, fire resistance and mechanical properties. However, there are still some problems for preparing polymer/layered inorganic compound nanocomposetes as follows: (1) Strong interaction between polymer and layered inorganic compound is necessary, which limited the intercalation of apolar polymer; (2) Polymerization of monomer involves complicated chemical reaction; (3) The organophilic process of inorganic compound needs complicated chemical reaction and separation between solid and liquid. (4) Melt intercalation needs low viscosity of polymer melt; (5) The inorganic compound with tight layers is hardly ion exchanged, or intercalated.
Solid-state shear exfoliation method is used in this study to prepare the polymer/layered inorganic compound nanocomposites based on our self-designed pan type milling equipment. This equipment has unique structure, and works like three-dimensional scissors. It can exert very strong shear forces on the materials to make the layers of fillers slip, or exfoliate interplanarly, forming platelets with high aspect ratio. In this case the exfoliation of graphite and the preparation of PP/graphite nanocomposites were realized. The experimental results show that when graphite and PP are co-milled together at ambient temperature, the size reduction of graphite and PP, the interlayer slide and exfoliation of graphite with weak interlayer structure, the good dispersion of nanosized graphite flake in PP matrix can be realized. And the network formed by interlaping of graphite flakes greatly contributes to the remarkable enhancement of electrical conductivity of PP/graphite composites at very low graphite loading, e.g., when graphite content is only 5 wt.%, the electrical conductivity of PP/graphite composites prepared by this technique reaches 1.1×10-4 S/m, 10 orders higher than the 1.1×10-14 S/m of the PP/graphite prepared by conventional mixing.