(343f) Enhancement of Electrical and Thermal Conductivity of Polypropylene By Graphene Nanoplatelets

Primary disadvantage of fiber reinforced polymer composites is its susceptibility to lightning strike due to poor electrical and thermal conductivities. A number of explorations are being made to improve these properties using nanotechnology. Graphene is as good as single walled CNT because of its 2-D configuration it potentially offers vapor barrier properties, yet inexpensive for practical applications. These properties are equally important in plastic industries. As a first step in this direction, graphene modified polypropylene polymer is being developed to improve its electrical and conductivities. Two techniques were investigated: surface coating and extrusion. Polypropylene pellets (3-4 mm) and graphene from XG Science Inc. (xGnP-5 & xGnP-25) were selected. Polypropylene pellets were coated with different weight percent of graphene by magnetic stirring followed by sonication. Then both neat and coated pellets were compression molded into circular disc of 75 mm diameter and 3 mm nominal thickness.  Nine different weight percent (0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 3.0, and 6.0) of xGnP-5 and four different weight percent (0.1, 0.5, 1.0, and 1.5) of xGnP-25 graphene-polypropylene nanocomposites were prepared along with base line polypropylene samples. The T-T-T and surface conductivity of all samples were measured. In case of coating technique the conductivity of polypropylene increased by 13 log cycles for about 1.0 wt. % addition of graphene. The percolation weight percent for both 5 and 25 µm size graphene was found to be 0.5 wt. % (or volume fraction is about 0.25%). Coating technique break the agglomerations due to magnetic stirring followed by sonication and gives homogeneously graphene coated polypropylene pellets. When polymer melts under compression molding, the graphene platelet network formed on the surface of polypropylene pellets as well as T-T-T of the molded disc, which provided continuous network of graphene. However, in extrusion technique graphene segregated and did not disperse properly in polypropylene.