Manufacturing strategy is of prime importance for the appropriate incorporation of filler into a polymeric matrix, and this in particular refers to nanofillers. Herein, direct-graphite nanoplatelets are used as filler in polystyrene. The as-received filler material contained microscopic size agglomerates formed by nanoscopic size graphite nanoplatelets. Refining of the microagglomerates (break-up) and production of, desirably, single graphene layers (exfoliation) is the ultimate target for controlling production and thus properties of the present materials. Several processing methods including microcompounding, roll-milling/calendering, Brabender mixing chamber, and solvent processing are used and compared with elongational flow mixing by a newly developed mixer. For the present system, sonication with surfactant assistance solvent processing yields both good micro deagglomeration and production of thin graphene nanostacks/layers. Also the elongational flow mixing efficiently refines the microagglomerates. Solvent processing and microcompounding are more efficient than the other processes in the production of exfoliated thin graphene stacks/layers. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013