How much surfactant should be used for emulsion polymerization?
Should it be more than CMC of surfactant?
Or does its concentration depends upon amount of hydrophobic monomer?
It really depends on the system but, I have used systems that are 20 vol% of the organic phase surfactant.
It might be used higher than the CMC and it uses usually in ratio to amount of monomer(s) to get the stable latex.
Hi, it really depends on many things: type and monomer amount, surfactant type, temperature, mixing conditions and mixing protocol and a big etc.
Start with 1 % surfactant based on monomer content and adjust according to your required results (particle size?). Follow some simple rule of thumbs:
* Use more surfactant (no more than 5 % based on monomer content) if you require a more stable emulsion or a smaller particle size.
* Increasing mixing speed also reduces particle size and size homogeneity, but to a limit since overmixing can produce emulsion instability or polymodal distributions.
* Use the higher monomer content possible, better if it is over 60 %; otherwise go for less than 30 % monomer. If around 50 % monomer is used, higher mixing speed is required in contrast to a much higher or much lower monomer content.
For a single batch system:
SLS = 1 to 2%
Monomer = 30 to 40 wt%
Water = the rest to 100%wt
For a batch system with continuous feed of monomer into the water maintain a ratio of surfactant to monomer >0.03 wt/wt. Adjust as needed for the type of monomer/s and final properties of polymer.
Consult the patent literature. There are plenty of polymerization recipes. Most likely your monomer-polymer emulsion polymerization system is fully covered in the patent literature.
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