Notes :

Graphene platelets dispersion guidelines for 55093 - Graphene Platelet Nanopowder (GPN Type 1)

Dispersion into Non-Aqueous Solvents:

Organic solvents are very effective in obtaining a good dispersion but, in most cases, are not practical for our customer to use. Much of the early development work with 55093 in thermoplastic resins was done by dispersing the platelets in an aromatic solvent, dissolving the
polymer in the same solvent, mixing the two solutions and then evaporating the solvent to obtain the thermoplastic with an excellent dispersion of platelets.

Isopropanol (IPA) is a fairly good solvent which is inexpensive and easy to use, but may not be as effective as some stronger solvents. Some very effect solvents include N-Methylpyrrolidone (NMP), Dimethylformamide (DMF), Tetrahydrofuran (THF), and Chloroform. However, these are very strong and toxic materials and should be handled with great care by experienced personnel. In any case, if solvents are used to aid dispersion into a polymer system, care should be taken to make sure
that the solvent is removed prior to further processing.

Dispersion into Aqueous Systems:

55093 Graphene Platelet Nanopowder (GPN Type 1) is hydrophobic and will not disperse in water without a dispersion aid. Three dispersion aids that we have proven to be useful are:

- Sodium dodecylbenzene sulfonate - (SDBS) - (solid)
-Linear or branched poly(ethyleneimine) - ((PEI) - (50% H2O solution)
-Poly(sodium styrene sulfonate) - (PSS) - (~70k Mw, 30% H2O solution)

Two methods have been used:
1. Add dispersant to water at 1-2% level and then add 55093 with the use of an ultrasonic mixer. The rate of 55093 addition to the liquid is critical. It should be added with continuous mixing, at a rate so that the 55093 does not coalesce on or in the liquid. A continuous feeding system (screw or vibratory) will be helpful. The addition rate may need
to be adjusted during addition since the receiving liquid may change viscosity during this operation due to concentration and temperature changes. Careful 55093 addition should result in a stable suspension. Experimentation with the amount of dispersant will be
necessary to determine the optimum level for your system.

2. Continue to sonicate the suspension from step for a few minutes or longer. Filter and wash the coated platelets. Now re-disperse the coated 55093 in the desired amount of water to obtain a stable suspension.

In addition to the above solvents, a mixture of 15 wt% IPA to 85 wt% water should result in a carrier solution into which our nanoplatelets can be dispersed with the aid of sonication. Normally, particles that settle out of a solution can be redispersed with the aid of an ultrasonic probe.

Dispersion into Thermoplastic Matrix:

While solvent dispersion will give the best results, it is not practical for volume production. Extrusion should yield good results, especially for lower viscosity thermoplastic resins, but it may
be necessary to experiment to determine the best method for your resin system.

-Some manufacturers have introduced specially designed screws for nanocomposites.
-If available, counter-rotating screws have shown good results in many materials.
-Lower melt viscosity will improve dispersion. This can sometimes be achieved by increasing processing temperatures or by switching to a polymer with a higher melt index.
-In general, mixing graphite nanoplatelets with powdered polymers, rather than pellets, result in better dispersion.
-Especially with resins in a powder format, it may be advisable to mix 55093 GPN Type 1 with powder before feeding into the extruder.
-Although feeding of pastes or liquids is not common, there may be special cases where a pre-dispersion of the nanoplatelets into a suitable carrier material could improve the results of the final composition. If the end use is in a polyolefin resin, the use of a pure hydrocarbon solvent would insure compatibility and a minimum of interference of any retained solvent in the final polyolefin properties.

Because of the importance of good dispersion and the difficulty involved, we recommend that you purchase a pre blended master batch. This will allow you add 55093 to your system with a
pelletized concentrate.

Dispersion into Thermoset Resin Matrix (Epoxies, Urethanes, etc):

For most resin systems, traditional mixing techniques should prove adequate. Sonication with an ultrasonic probe works well. Also, good results have been obtained with a high-shear 3 roll mill. A balance must be stuck when using high shear mixing since prolonged use cause the platelets to deform.
The rate of 55093 addition to the resin is critical. It should be added with continuous mixing, at a rate so that the 55093 does not coalesce on or in the liquid. A continuous feeding system (screw or vibratory) will be helpful. The addition rate may need to be adjusted during addition since the receiving resin may change viscosity during this operation due to concentration and temperature changes. Careful 55093 addition should result in a stable suspension. Do not store the dispersed blend for long periods since the platelets will settle over time. The rate of settling is dependent on the viscosity of the subject resin. To prevent settling and reagglomeration react the resin suspension as soon as possible. Normally, particles that settle out of a
solution can be redispersed with the aid of an ultrasonic probe or other high-energy mixing system.

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