Evaporation-freezing and rheological behaviour of chitosan dispersions at different temperatures and with different molecular weights using glycolic acid as anionic systems were studied. Chitosans 2.000.000 (HC), 750.000 (MC) and 70.000 (LC) were employed alone or as mixtures (HC/MC, HC/LC, MC/LC 1:1 w/w). Different concentrations of glycols were added to these base dispersions (propylene glycol and glycerine) to investigate how the above physical properties change. The different rheological and evaporation-freezing behaviours of chitosan dispersions were related both to the molecular weight of chitosan and the vehicle composition of the dispersions. Particularly, the rheological study showed a pseudoplastic and shear thinning behaviour for all chitosan dispersions with flow index values n, tending to < 1 at increasing molecular weights. Chitosans dispersions containing glycols showed lower apparent viscosity values than the base dispersions of the corresponding chitosans, but the water loss and the freezing point were lower especially for chitosan dispersions containing glycerine. This work presents a wide range of dispersion series from which to choose the most suitable to formulate pharmaceutical and cosmetic products.
Physical properties of chitosan dispersions in glycolic acid
MACCIONI, ANNA MARIA;
2004-01-01
Abstract
Evaporation-freezing and rheological behaviour of chitosan dispersions at different temperatures and with different molecular weights using glycolic acid as anionic systems were studied. Chitosans 2.000.000 (HC), 750.000 (MC) and 70.000 (LC) were employed alone or as mixtures (HC/MC, HC/LC, MC/LC 1:1 w/w). Different concentrations of glycols were added to these base dispersions (propylene glycol and glycerine) to investigate how the above physical properties change. The different rheological and evaporation-freezing behaviours of chitosan dispersions were related both to the molecular weight of chitosan and the vehicle composition of the dispersions. Particularly, the rheological study showed a pseudoplastic and shear thinning behaviour for all chitosan dispersions with flow index values n, tending to < 1 at increasing molecular weights. Chitosans dispersions containing glycols showed lower apparent viscosity values than the base dispersions of the corresponding chitosans, but the water loss and the freezing point were lower especially for chitosan dispersions containing glycerine. This work presents a wide range of dispersion series from which to choose the most suitable to formulate pharmaceutical and cosmetic products.
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