ИСТИНА

Graphite nanosheets (GN) are very popular nowadays as carbon filler for composites due to the low cost, low percolation threshold and easy way of manufacturing. Adding less than several percent of GN to the polymer promotes increase of thermal conductivity and decrease of water sorption. Most researches are devoted to ultrasonification of graphene oxide or its reduced form to get GN. Herein we report the investigation of ultrasonification of expandable graphite and expanded graphite of different natures in different solvents. The expandable graphite dispersion was found to take place easier when polar proton liquids are used and become less effective when 50% aqueous solution of ethanol is replaced by the solution of isopropanol of the same concentration. The most effective dispersion of expanded graphite was achieved by successive treatment in ballmilling and ultrasonification in n-methyl-pyrrolidone (NMP) and in water. Water was chosen for the following study. Two types of ultrasonification were applied. First, a static one when both ultrasonic irradiator and dispersive liquid were motionless. In the second case, the dispersive solution was cycling around the ultrasonic irradiator. The second technique allows to obtain stable for months dispersions by sonification only for 40 minutes, whereas the first technique takes several days to get the same result. In all the sonificated materials graphite structure remained almost the same to initial graphite. Expanded graphite is easier dispersed than others graphite materials.