Latex Stability Problem Due to Addition of Filler

Manufacturer: We are adding filler to our latex compounds to reduce cost while increasing modulus. However, every time we do this we encounter a lot of problems due to a drop  in latex stability.

 
John Woon (Senior Latex Consultant): You did not tell me your stabilizing system and how much stabilizer you are using. The problem you encountered is due to the fact that the stabilizers of the rubber particles are being "robbed" by the filler.

As a general rule, the level of the stabilizer (i.e.surfactant) added should be proportional to the quantity of filler added. Also, the level of stabilizer added to the filler that is in the form of a aqueous dispersion (or slurry) is lesser compared to the case when the filler is added as dry powder.

You should also take note that the lower the particle size of the filler, the higher is the level of the surfactant required.

Sometimes a blend of more than one surfactant works better than when only a single surfactant is used.