These are stable and fine particle sized ( typically 0.05 microns ) dispersions of oxidized polyethylene wax ( MARCUS 3400 & 3500 ) in water. The stability is attained by the inclusion of a surfactant into the wax during the emulsification procedure. There are three main types of emulsions used in practice and these are:-
Anionic
The surface active portion has a negative charge and is normally a fatty acid in combination with an amine. The acid commonly employed is oleic acid and there are many amines which can be used and differing ones are chosen depending upon the application. Among the most used are Morholine, Amino-methyl-propano (AMP) Diethylaminoethanol ( Diethylethanolamine ) and Ammonia ( 25-28% ).
Non-ionic
This class of emulsion has no charge and an ethoxylated nonyl phenol or alcohol is the most suitable choice ( with an ethoxylation degree of 9-10 moles EO ) although a small amount of saponifying agent is also incorporated. This is usually potassium hydroxide.
Cationic
These emulsions have a positive charge and as a consequence, exhaust very well onto negatively charged surfaces. The preferred type of surfactant is an ethoxylated amine ( with an ethoxylation degree of 2 moles EO ) and it is used in combination with a small amount of acetic acid.
Another type of surfactant which can be used and has very useful properties is an imidazoline but again, must be used in combination with acetic acid.
There are a number of different ways of preparing polyethylene emulsions, the most widely used being the wax to water method and the pressure emulsification technique.