Preparation Of Salt-Resistant Superabsorbent Resin Induced By Glow Discharge Electrolysis Plasma

Plasma, also called the fourth state of matter, is composed of positive ions, negative ones, electrons, and neutral species. It is considered as a nice kind of electric conductor. In fact, 99% of the matters in the universe exist in the form of plasma. There are two kinds of plasma mainly used in laboratory: the high-temperature plasma and low-temperature plasma.Glow discharge electrolysis plasma is a kind of low-temperature plasma, coming from the non-faradic electrochemical process. During the process of electrolysis, the water is boiled away by the glow generated between the needle-like anode to form the steady steam sheath when the voltage between the two electrodes is high enough, forming a lot of active species such as H·,·OH, H₂O₂, e^-_aq and HO₂·. Such a sort of active species could give rise to many chemical reactions in aqueous soultion. Therefore, they can be used as an initiator of chemical reaction. This paper consists of four parts, studying in detail the application of glow discharge electrolysis plasma in the synthesis of salt-resistant superabsorbent via solution polymerization.Chapter 1. The characteristics of plasma, method to produce cold plasma, as well as its application fields are introduced in brief. The formation, application and development of glow discharge electrolysis plasma are also recounted. This chapter also makes an introduction of progress, preparation and characterization method, performance evaluation indicator, application area and salt-resistance melioration of salt-resistant superabsorbent.Chapter 2. The graft polymerization of acrylic acid and acrylamide on starch is carried out by using the glow discharge electrolysis plasma to modify starch's properties. Using acrylic acid (AA) and acrylamide (AM) as monomers and N, N'-methylenebisacrylamide (NMBA) as crosslinker, some effects on the graft polymerization, such as the applied discharge voltage and time, the concentration of crosslinker, the molar ratio of AA to AM and the neutralization degree of AA are investigated. Results show that a satisfactory starch-graft-acrylic acid- acrylamide superabsorbent resin with high absorbency (821 g/g in distilled water, 80 g/g in 0.9% NaCl solution) is obtained. A faster swelling-ratio for saline solution is observed to be 75% within 10 min. The product is characterized by means of the Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), revealing that the monomers are effectively grafted to starch. The convenient and effective technique can be used to get superabsorbent with advantages of high water absorbency, high absorbent speed, excellent resistance to salts in performance.Chapter 3. Salt-resistant superabsorbent terpolymer is synthesized via solution polymerization initiated by glow discharge electrolysis plasma, in which acrylic acid (AA), acrylamide (AM) and 2-hydroxyethyl methacrylate (HEMA) are used as monomers and N, N'-methylenebisacrylamide (NMBA) is used as crosslinker. The synthetic conditions such as the applied discharge voltage and time, the concentration of crosslinker, the molar ratio of AA to AM and the neutralization degree of AA are also studied. The resulting product is characterized by fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The swelling capacity for pure water and 0.9%NaCl solution are found to be 996 g/g and 82 g/g, respectively. A faster swelling-ratio for saline solution is observed to be 67% within 10 min.Chapter 4. In order to improve salt tolerance of the resin, sodium methylallyl sulfonate (SMAS) with sulfo group is employed as one of the monomers. Salt-resistant superabsorbent composite is prepared via aqueous solution polymerization initiated by glow discharge electrolysis plasma. Using acrylic acid (AA) and acrylamide (AM) as another monomers and N, N'-methylenebisacrylamide (NMBA) as crosslinker, some effects, such as the applied discharge voltage and time, the concentration of crosslinker, the molar ratio of AA to AM and the neutralization degree of AA, on swelling ratio for saline solution are also studied. The swelling ratio for pure water and 0.9%NaCl solution are found to be 1180 g/g and 95 g/g, respectively. A faster swelling-ratio for saline solution is observed to be 72% within 10 min. Moreover, the proposed superabsorbent exhibits excellent properties in intensity, dispersion and springiness.