Preparation And Properties Of Poly(aryl Ether Ketone)/Nanographite Composites With High Dielectric Constant

Driven by ever growing demands of excellent thermal, chemical stability, highdielectric constant and low dielectric loss for microelectronic products, high dielectricconstant nanocomposites have been hot topics. Nanocomposites composed ofpolymer matrices with inorganic metal particles of less than100nm in size havebeing considered for applications such as interior and exterior accessories forautomobiles, structural components for portable electronic devices and embeddedpassives. Recently, although most nanocomposite research have focused oninorganic metal particles, the same nanoreinforcement concept can be applied toanother layered material, graphite, to produce nanoplatelets and nanocomposites.Graphite is the stiffest material found in nature, having a modulus several times thanthat of inorganic metal particles, and also with excellent electrical and thermalconductivity. The key to utilizing graphite as a platelet nanoreinforcementis in the ability to exfoliate this material. Also, if the appropriate surfacetreatment can be found for graphite, its exfoliation and dispersion in a polymermatrix will result in a composite with not only excellent mechanical properties butelectrical properties as well, opening up many new structural applications such aselectromagnetic shielding and high thermal conductivity.In this work, a series to fabricate exfoliated nano-scale graphite platelets wereproduced, which were modified to achieve a better dispersion in polymer matrix.Using percolation theory, this work revealed the connection between themicrostructure of composite materials and dielectric properties. With metalphthalocyanine well dispersing in the matrix, we also studied the dielectric propertiesof the nanocomposites. In the first part, exfoliated graphite nanoplatelets were obtained from naturalgraphite. The graphite nanoplatelets were formed through rapid heat and ultrasonicpowder. Then these platelets were chemically modified with sulfuric acid and nitricacid, which improved the dispersibility in the organic solvents and polymers. The sizeof the resulted graphite platelets was0.5~5um in diameter and5~30nm in thickness.Novel a-GNs/SPAEK nanocomposites, with high dielectric constant and lowdielectric loss, were prepared by using a solution blending technique. We studied themicrostructure and dielectric properties of composite materials, the results showedthat the dielectric constant was about800at1000Hz when the volume fraction ofa-GNs was5.5vol%. The percolation threshold of the a-GNs/SPAEK composites was3.2vol%of a-GNs and the dielectric constant could get135. The composites alsoshowed well thermal and chemical stability.In the second part, nanocomposites composed of SPAEK matrix with4,4’,4’’,4’’’-phthalocyanine tetraamines(4NH2-CuPc) and a-GNs were produced.Compared these composites with a-GNs/SPAEK composites, the former had betterdispersion in the matrix. The introduction of CuPc coating had improved a-GNsdispersion, limited the formation of conductive network and reduced the dielectricloss of the composites from2.56to0.8(a-GNs was3.2vol%,1000Hz). The resultsalso showed that the frequency had less effect on the dielectric constant of thea-GNs@CuPc/SPAEK nanocomposites than the dielectric constant of thea-GNs/SPAEK nanocomposites. At the same time, the composites also showed wellthermal and chemical stability.