What Are The Best Surfactants For Latex Compounds?

Manufacturer: We are manufacturers of latex dipped products using both natural rubber latex and synthetic latices. Our latex compounds are varied with some having low pH while others high pH. We would like to seek your advice on the choice of surfactants as effective stabilisers for our compounds. We've seen and sought the input from the suppliers of surfactants but although they have expertise in surface active agents, they lack knowledge of latex technology.

John Woon (Senior Latex Consultant): There are indeed many choices of surfactants in the market so much so that it could be very confusing and daunting experience in selecting the right surfactants for the right compounds especially to the new latex technologist.

I shall attempt to make it as simple as possible for you in my explanation and suggestion.

Generally, surfactants could be classified under four main groups, namely anionic, non-ionic, cationic and amphoteric.

My advice for you is to concentrate on the anionic first while keeping the non-ionic group in view only for specific conditions. Anionic group itself in turn could be further classified under carboxylates, sulphonates, sulphates and phosphates:

1) Carboxylates
For highest solubility and hence best stability, use the potassium soap. Use the ammonium soaps when the final films are to have the least water sensitivity especially when leaching could not be sufficiently done. I shall explain why you should stay away from the sodium soaps separately.

Good examples are potassium oleate, laurate and caprylates. However these are sensitive to acids and heavy metal ions.

2) Sulphonates
For your compounds with low pH, carboxylates might not be effective. I suggest you try the sulphonates which are less sensitive to acid (low pH) and dissolved heavy metal ions. This could be added in combination with the carboxylates.

3) Sulphates
This is more soluble than sulphonates and are even more superior in terms of resistance to low pH and free metallic ions.

Notes: Both sulphonates and sulphates are also good wetting agents which might be useful in your applications but they might retard the gelling process where calcium nitrate is used as the coagulant. For your purpose you also could use a combination of say, potassium laurate and sulphate.

4) Phosphates
These are mainly the inorganic polyphosphates. This has the mildest surface active agent. I'd discuss how and where you should use this along with the non-ionic surfactants separately.

Note: Amphoteric surfactant could be another good candidate for your compounds which are more acidic.