Directly Mixing The Preparation Of Expanded Graphite Conductive Master Batch

Vermicular expanded graphite (EG) has a big bulk volume because of small apparent density. The graphite sheets are tangle with each other with big open and close pores in it which leads to easy agglomeration and difficulty in mixing with polymers. It may consume much energy in industrial manufacture to achieve well-dispersed materials. Thus, EG should be modified before use in order to solve this problem.Master-batch process is a new way in the preparation of polymer/EG conducting composites. According to the advantages of in-situ polymerization and direct melt blending, EG was first pretreated to be well-dispersed concentrates (i.e. master-batch). Then, blending this modified graphite (MG) as a kind of filler with other polymers. Polymer/EG conducting composites were prepared by master-batch filling process. The effect of different preparation methods and different carriers on EG dispersion state were studied in this article. The electrical and mechanical properties prepared by master-batch process and direct-melt blending process were compared in assistance with XRD, SEM, DSC. The relationship between structures and properties was elucidated systematically.Results showed that EG master-batch modified by in-situ polymerization of MMA monomer had excellent electrical properties. However, it was hard for MMA to cure when EG content higher than 20 wt% which limited its uses. Another investigation showed that EG tangled structure was almost destroyed into isolated pieces when direct melt-blended EG with PMMA resin. From this point of view, master-batch process had successfully achieved nanoscale dispersion of EG. In addition, polymer/graphite nanocomposite could be easily done by master-batch filling technique without the complicated process that graphite nanosheets were first made by sonication.Crystalline PE and noncrystalline PS were studied as carriers in the preparation of EG master-batches. Electrical, mechanical and thermal properties of HDPE/EG composites made by master-batch filling process showed a perfect master-batch content of 60 wt% where the percolation threshold was very low and its mechanical and thermal properties were also enhanced.