凯发

Polyolefins are excellent polymeric matrix for nanofillers due to their low cost, high performance, low density, recyclability, high processability and versatility. Graphene is a potential nanofiller due to its outstanding properties as strength, stiffness, thermal and electrical conductivity, high surface area and lightness. Its use in nanocomposites could produce polymeric materials with electrical conductivity with possibility to be used in electromagnetic radiation shielding, antistatic coatings, flexible electrical devices, transducers, etc. Brazil is the third largest producer of graphite, preceded by China and India, having large reserves. The main problem in obtaining nanocomposites is the homogeneous dispersion of the nanoparticles in the polymeric matrix. Graphite has been introduced into polyethylene or polypropylene to form composites or nanocomposites through fusion of the polymeric matrix and intercalation in solution; however in situ polymerization has been less used. Our research group has been working during the last years on the synthesis of nanocomposites of polyethylene, polypropylene and copolymers with graphite nanosheets by in situ polymerization using metallocene catalysts. In order to reduce the percolation threshold different methods of exfoliation of graphite were used. Different types of graphite such as graphite oxide and reduced graphite oxide with few graphene layers were tested. The method of polymerization was also studied using the noncovalent or the covalent approach. The increase in the graphite content permitted to transform isolating materials as the polyolefins in semiconducting materials. The results were highly influenced by the exfoliation of the starting material and also by the method of polymerization.
In this presentation there will be shown our last results in polyolefin nanocomposites using different graphite and also there will be done a brief exposition about the graphite industry in Brazil.