Dear Mr. Mohit,

I understood that you are looking for a dispersant and a binder agent. It is important to note that they are diferent kind of additives. Dispersants give stabilization to the slurry, taking the particles away for each other and avoiding aggregates and floculation. This is a target when we aim to produce high density and, as well, high green strenght. A binder is also important to achieve high green strength, but it acts in the slurry creating a three dimensional network that would take the particles in such way that helps to get high density too. It would also gives more flexibility to the green body, helping to hold all together. Both change the rheological properties of the slurry once they are changing the inner structure of it.

As a dispersing agent I would suggest DARVAN C-N, from Vanderbilt Minerals. It is a ammonium poly methacrylate, and after burning, theoretically, everything is decomposed into gases, insted of other dispersing agents as sodium poly methacrylate whose sodium atoms remains in the solid material. As you are working with hydroxyapatite generally it is great to avoid this kind of contamination. (Send an e-mail to Vanderbilt Minerals asking for a free sample, they are very kind)

As a binder I would indicate carboxymethylcellulose. With small quantities you can achieve higher binder effect than in PVA. However, in such case it may not be suitable with so high solid loading (60 wt%). It is also known as a plasticizer agent. Lower quantities of binder may be interesting also because they would leave the material with less probability of inducing defects. The binder is quite related to the processing method that would be applied to achieve the green bodies because it communly afects the rheological properties of the slurry.

Best reguards

 The bacteria which stick to teeth surfaces, which are mainly hydroxyapatite, use dextran and related glucans to maintain an adherent biofilm. It might be useful to try dextran in your application. There are also water-insoluble glucans related to dextran that could prove useful.

In India, Prof. Arun Goyal works in this area, and may be able to provide further advice.

Ammonium Poly acrylate like Darvan C, Darvan 821 A from Vanderbilt Minerals, Dispex A 40 from CIBA will work well as dispersant for your material. As per my practical experience, if slurry is properly optimized with dispersant content, you will get good green strength even without binder provided your hydroxyapatite powder property is good ( particle size distribution, particle morphology, surface area etc).