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Question: "What are the advantages and disadvantages of different types of suspending agents in formulation of a suspension? Which are the best suspending agents?"
 
Reply
  The answers to these questions are just what people expect from short courses on colloid chemistry. In essence the question is: What is the ingredient I can add to my formulation to make it perform the way I want? Simple answers are to take the course, buy the book, hire the consultant, etc. But let me suggest a direct approach you might find helpful.
   
  First, go to suppliers of surfactants. They are the people most interested in getting the best possible material into your hands. I have searched the web and found some useful sites

Surfactant suppliers providing on-line help


    Byk Chemie             (http://www.byk-chemie.com/gbn/frame.cfm)
    Schibley Chemical   (http://www.schibley.com/surfactants.html)
    Surfactants, Inc.     (http://www.surfactantsinc.com/formulary.asp)
   

Of these, the one that has been best for me and for people I have worked with is Byk-Chemie. I hesitate to make such a specific choice, but I’ve seen great results. Others may be just as good, or even better.


Many companies manufacture surfactants as part of their product portfolio. I have look across the web for those that have on-line help in selecting surfactants. Some are:


Surfactant manufacturers providing on-line help

   

Akzo Nobel          (http://www.akzonobel.com/com/Chemicals/Products.htm)

    Arizona Chemical (http://www.arizonachemical.com/products/)
    BASF                   (http://www.basf.com/performancechemical/bcperfapplications.html)
    Cognis                (http://www.cognis.de/framescout.html?/BusinessUnits.html)
    DeForest Enterprise (http://www.deforest.net/deforest1.htm)
    Dow Chemicals     (http://www.dow.com/surfactants/products/ethylene.htm)
    McIntrye Group     (http://www.mcintyregroup.com/productfinder_web.cfm)
    Rohm and Haas    (http://www.rohmhaas.com/directory/prototype/search.htm)
     
  With a little search you should be able to get some ideas. Certainly talk to these suppliers. They can be quite expert.
   
  Second, pay attention to the types of surfactants they recommend. Are they ionic or polymeric; water soluble or solvent based; anionic, cationic, or amphoteric? Learn what these terms mean. Are the surfactants part of a graded series, say of varying molecular weight, or acid number, or water solubility, or HLB? Can you understand what this means in your application?
   
  Third, search the patent literature. You certainly know the key words from your own business. Pay attention to key words used by the technical representatives of these companies when they describe performance expectations. This should be enough to get useful patent information.
   
  Fourth, experiment. Be sure to test the surfactants over a range of concentrations. This can vary widely from application to application. Allow time for mixtures to equilibrate –wait overnight before evaluating any performance, adsorption is slow.
   
  Fifth. If you have found the magic ingredient, you’re done, great. And you’ve saved the cost of a short course. If not, see you in our next class and we’ll work through the problem a little more systematically and, it is to be hoped, lay a plan for the next steps.

 


 
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