Graphite Powder Application
Graphite is one of the new conductive filler, the more commonly used carbon black has good conductivity, low friction loss, low pollution, and other advantages, while the expansion of graphite to join can greatly improve the conductivity of polymer materials so that the polymer appears from the insulator and semiconductor transformation.
Therefore, it has an important application value in conductive composites.
The following is about how expanded graphite can be used as a conductive filler to prepare polymer-based conductive composites.
The expanded graphite is made into expanded graphite, and then the expanded graphite is dispersed in the polymer matrix in nano-graphite flakes to produce polymer-based nano-conductive composites. As the graphite in the matrix was nano-dispersed, so the mechanical properties of the matrix are not much, while the graphite was lamellar, so it is easy to form a conductive network in the matrix, the amount of graphite is small enough to achieve a good conductive property, these are the other conductive filler can not do.
Therefore, the expansion of graphite as conductive filler preparation of polymer-based conductive composites has become a hot spot in recent years.
Expanded graphite as a conductive filler preparation of polymer-based conductive composites can be used in situ polymerization intercalation method. The expanded graphite is dispersed in 70% ethanol aqueous solution, ultrasonically dispersed for 8h, filtered and dried to obtain nano-graphite flakes, and then the nano-graphite flakes are mixed with methyl methacrylate monomer and then polymerized to obtain polymethyl methacrylate / nano-graphite composite, the conductive osmosis threshold value of the composite is only 1.0%, much lower than that of the polymethyl methacrylate / common graphite composite. The electrical conductivity of the composites reached 103S-cm when the mass fraction of nanoflake graphite was 4.0% with a conductivity overshoot threshold of 5.5%.
In addition, nonconductive composites of polystyrene and polyamide with expanded graphite were prepared and studied by in situ polymerization intercalation method.
Expanded graphite as a conductive filler and polymer composite can also be used expanded graphite and polymer mixed intercalation methods, mixed intercalation methods are solution intercalation and melt intercalation method of two kinds. Solution intercalation method to obtain conductive composite materials, the conductive electrical conductivity of good performance, conductive osmosis threshold of about 2% (volume fraction) or so, but the preparation process is complex and consumes a large number of organic solutions, process costs are high, the practical application is not significant. The melt intercalation method is the most promising method, but the direct expansion of graphite and polymer melt intercalation of conductive composites obtained by the conductive properties of the poor conductivity, conductivity over-permeability threshold value of high. The first expanded graphite by surfactant treatment and then with polymer melt intercalation, the process is simple, and the resulting polymer-based conductive composite has excellent conductive properties, conductivity overshoot threshold value is lower.
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