Ricerc@Sapienza

Over the past years, there has been an increasing interest in natural ester insulating liquids for application in power transformers, thanks to their higher environmental compatibility and lower fire point, as compared to conventional mineral oils. The main function of a transformer oil is its ability to dissipate heat, while ensuring electrical insulation. Among the various influencing parameters, it is well known that heat exchange in a liquid is also affected by its viscosity.

The effects that an increase of environmental pH has on the triple helix of scleroglucan (Sclg)
and on the Sclg/borax hydrogel are reported. Rheological experiments show that the hydrogel is less
sensitive to pH increase than Sclg alone, while at pH = 14 a dramatic viscosity decrease takes place for
both systems. This effect is evidenced also by the reduced water uptake and anisotropic elongation
detected, at pH = 14, by the swelling behaviour of tablets prepared with the Sclg/borax system.

Knowing the ability of water and bile salts to promote the reverse wormlike micelle growth in lecithin/water or lecithin/bile salt mixtures in oil, this work was aimed at elucidating the association properties of the three solutes lecithin, water and the bile salt (BS) sodium deoxycholate in cyclohexane. By systematically changing the fraction of the two additives (i.e.: water and BS) we could identify a region at low additive/lecithin molar ratios where stable wormlike micelle dispersions were formed.