Study On The Hydration Behaviors Of (Poly)Acrylic Acid/Sodium Chloride

The master thesis mainly studies three interrelated fields: the accuracy of Differential Scanning Calorimeter (DSC) of TA Instrument through comparing the DSC-2910 of TA with the ideal model; the research of the hydration behavior of the acrylic acid aqueous solution and sodium chloride aqueous solution; the research of the hydration behavior of the poly(acrylic acid) aqueous solution.Thermal analysis is one of the favorite characterization tools to research the hydration number of the chemical reagents, the accuracy of the characterization tool is quite important. The design defect in the furnace of DSC-2910, manufactured by TA Instruments, has been studied by determining a series of latent heats of stearic acid and zinc at different heating and cooling rates. In this DSC apparatus, there is a direct metal join between the sample and reference support, through which the measured sample leaks its heat energy to the reference. The low-level influence of the heat energy leakage can be corrected to some extent through prior calibration process during the experiment process without phase transition. Whenever a phase transition occurs, the leakage extent surpasses the ordinary one, so the prior calibration becomes invalidated, which causes the detected latent heat values obviously deviate the real one greatly. However, the latent heats of zinc determined by DSC-Q20, manufactured by TA Instruments, are well reproducible and equal to the real value approximately for the sample's heat energy leakage has been reduced greatly.The hydration behavior of acrylic acid aqueous solution has been studied by DSC. The results show that the solvation effects of acrylic acid aqueous solution with diverse volume fraction ranges are significantly different. With the content of acrylic acid increasing, there are the water-rich phase, the acrylic acid-rich phase, the acrylic acid-high-rich phase and two-phase coexistence state in sequence in the acrylic acid aqueous solution. This suggests that the acrylic acid solution is just a homogeneous solution in a certain fraction range(54.8%~70%), but there exist two phases in the aqueous solution outside the range. The hydration behavior of sodium chloride aqueous solution has been studied by DSC.The results show that the relative contents of the free water, the bond freezable water and the unfreezable water have an important influence on the dissolution of NaCl. When the concentration of the NaCl aqueous solution is less than 20%, there are three different states of water in the solution: the unfreezable water, the bond freezable water and the free water. When the concentration of the NaCl aqueous solution is more than 20% and less than the saturated concentration, there only exist two states of water: the unfreezable water and the bond freezable water. When the solution is in the saturated state, the relative content of the bond freezable water reaches the lower limit to dissolve NaCl.The hydration behavior of poly(acrylic acid) aqueous solution has been studied by DSC. The results show that with the concentration of poly(acrylic acid) aqueous solution increasing, the mass fraction of the free water, the hydrated water of the unit mass of poly(acrylic acid) and the hydration number of poly(acrylic acid) decreased gradually, but the mass fraction of the hydrated water increased gradually. The results of the fraction of free water and solvated water by TG are close to the results by DSC.