Modes of action
An examination of emulsifiers offered for cold processing shows they fall into distinct groups. Those for w/o emulsions tend to be polyglyceryl esters; for o/w emulsions there is a predominance of alkoxylated alcohols and phosphorous compounds; there is a group of silicone-based emulsifiers; and a number based on polymer chemistry. Most emulsifying systems work by reducing surface tension but it is also possible to make stable emulsions using polymers that hold the internal phase droplets in suspension. An example of these is the Rheosol range from Rheolab Laboratories, which are based on acrylate or polyacrylate polymers and are supplied pre-dispersed in oils or esters to which the aqueous phase can be added with rapid stirring. Anionic and cationic versions are available, they do not require a neutralisation step and other oil phase ingredients may also be added.