Influence of surfactant addition on the rheological properties of aqueous welan matrices

Autori: S. Manca, R. Lapasin, P. Partal, C. Gallegos
Presentato al: Southern Europe Conference on Rheology
Anno: 1999
Volume: 1
Issue: Unico
Casa Editrice: SIR-Cuen Napoli
Lingua: English


Abstract
The role of surfactants is essential to provide long term stability to emulsions since they prevent droplet coalescence by adsorbing at the o/w interface and increasing the repulsive interactions among droplets. Another way of enhancing the stability of emulsions and other disperse systems is based on the addition of polymers as thickening agents. Their efficiency depends on polymer concentration in the aqueous phase as well as on the structural features of the aqueous polymer system. Indeed, the formation of a weak gel-like polymer network in the continuous phase leads to very high viscosities in the low stress range and impart additional elastic properties to the whole system so that emulsion creaming is strongly inhibited. Several aqueous polysaccharide systems exhibit weak-gel properties, even at low polymer concentration, in a sufficiently large temperature range and, hence, could be considered 'a priori' as valid candidates to display such a stabilizing role in emulsions. However, the creaming stability of emulsions containing polysaccharides can be sensitive not only to the biopolymer concentration but also to surfactant-biopolymer interactions, depending on the nature of surfactant.


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