I am trying to use different oil soluble surfactant to stabilise my inverse emulsion. Out of these span 80 and span 20 suitable for my system. Could any one please reply which one is more suitable ?. Any inputs from your end would be great.
My first guess would be SPAN 80. In contrast to span 20 it is based on oleic acid. Hence, SPAN 80 has a more bulky alkyl part . Therefore the packing parameter will probably be more advantageous for water-in-oil systems. This is also indicated by the HLB value of SPAN 80 which is about 4.3. HLBs between 3-8 usually mean that the respective surfactant is suitable water-in-oil emulsions.
SPAN 20 has an HLB above 8. This means it is probably better for oil in water emulsions.
However, HLB values are more a kind of educated guess. For more information of the HLB you should have a look at:
http://www.firp.ula.ve/archivos/historicos/76_Book_HLB_ICI.pdf
SPAN 80 or you can say SMO will be good. but please try to check the HLB values of Oils which you are using for emulsification. Also try to avoid excess use of SPAN 80 it will affect you emulsion stability in other way.
Span 20 (Sorbitan Monolaurate) and Span 80 (Sorbitan Monooleate)
Both are sorbitan fatty acid esters/sorbitan monoesters, consisting of a series of mixtures of partial esters of sorbitol and its mono- and dianhydrides with fatty acids. The main differences between them are in (1) Hydroxyl value: Span 20 is ranging from 330-358, while Span 80 from 190-215 (2) Saponification value: Span 20 is ranging from 158-170, while Span 80 from 145-160 (3) HLB value: Span 20 is 8.6, while Span 80 is 4.3 (4) Surface tension: Span 20 is 28, while Span 80 is 30. Obviously, Span 20 is more hydrophilic than Span 80 and produces more stable o/w emulsions and microemulsions.
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