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Sulphonated lignin molecules in general do not possess the amphiphilic structure of conventional surfactants. Even so, they do have pronounced hydrophobic properties and will for that reason adsorb at the oil/water interface, building up a condensed interfacial film. The viscoelastic (mechanical) properties of this adsorbed layer provide good stability against coalescence.
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The most important property to any emulsion is its stability. There are two types of additives which help to stabilise emulsions; emulsifiers (reduce surface tension thus lowering the energy required to form a droplet) and emulsion stabilisers (prevent the formed droplet from coalescing). Our lignin-based products belong to the latter group, and stabilise the emulsion through three different mechanisms:
- The introduction of a electrokinetic charge at the o/w interface
- The formation of a semi-rigid interfacial film at the interface
- Steric interactions
Lignosulphonate dissolved in the water phase (left) adsorbs onto the oil droplets during emulsification and stabilises the emulsion towards creaming and phase separation (right).
The use of our products offers the emulsion manufacturer the following benefits:
- Stability to pH: emulsions stabilised with sulfonated lignins remain stable under extreme pH fluctuations.
- Stability to temperature: most lignin stabilised emulsions are highly resistant to heat and will remain stable in pressurised systems at 100ºC, and are resistant to breaking at 0ºC
- Stability to electrolytic contamination: hard waters, and even seawater can be utilised to prepare emulsions when used in conjunction with lignin based additives.
- Stability to handling: mechanical jarring, pumping or jetting has no detrimental effect on the stability of lignin stabilised emulsions. Gentle agitation is often sufficient to redisperse creamed emulsions
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Created:12.09.2005 22:20:17 Modified:11.07.2006 16:03:31
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