The Effect of Temperature on the Mechanical Properties of Alginate Gels in Water/Alcohol Solutions.

Alginate organohydrogels prepared in water/alcohol mixtures play an important role in electronic and superconductor applications in low-temperature environments. The study deals with the preparation of Ca-alginate organohydrogels and the analysis of their equilibrium swelling and mechanical properties at sub-zero temperatures. It is shown that the equilibrium degree of swelling at room temperature is noticeably affected by the concentration of co-solvents (methanol, ethanol, and 2-propanol) in the mixtures and the number of carbon atoms in the co-solvent molecules. Mechanical properties are studied in small-amplitude oscillatory tests. The data are fitted with a model that involves three material parameters. The influence of temperature is investigated in temperature-sweep oscillatory tests under a cooling-heating program, where a noticeable difference is observed between the storage and loss moduli under cooling and heating (the hysteresis curves). The hysteresis areas are affected by the cooling/heating rate and the number of carbon atoms in the co-solvents.