Study On The Synthesis And Properties Of Salt-Resisting Superabsorbent Based On Maleic Anhydride

In this thesis,three kinds of different superabsorbents were prepared by aqueous polymerization using several kinds of different monomers,and both the properties of the resultant superabsorbent and the variables that had influence on the properties of the superabsorbent were mainly discussed in this thesis.The main results were obtained as follows:(1) As the effects of PVA content on water absorbency of the resultant superabsorbent reported by the literatures were not identical.A superabsorbent with semi-interpenetrating network was prepared by solution polymerization using maleic anhydride(MAH),acrylamide(AM) and poly(vinyl alcohol)(PVA) as raw materials. The effects of PVA content on water absorbency,swelling rate and salt sensitivity to saline of the superabsorbent were examined in detail before which the synthesis conditions were optimized.The results showed that with the increment of PVA content, the water absorbency of the resultant samples would first decrease and then increase.In addition,the samples would have higher swelling rate and became less sensitive to saline.(2) As the water absorbency of the first superabsorbent is very low,a superabsorbent with improved water absorbency in physiological saline was prepared by solution polymerization in which a strengthened ionic monomer was added into reaction mixture. But the results showed that such method can only work when the superabsorbent was immersed into solutions containing monovalence cations.When immersed into solutions with higher valence cations such as A1³⁺ the superabsorbent still had low water absrorbency.So the previously mentioned method can not fundamentally solve the problem that most superabsorbents have poor salt-resistance properties.Comparing with the effect of cations with different valence on water absorbency of the superabsorbent,the effects of anions with different valence on water absorbency of the superabsorbent seem much less.Besides,we also found that the resultant superabsorbent had nice water-retention properties.Even being dried for 6 h at 90℃,the superabsorbent can retain more than half of its original absorbed water,as a result of which the superabsorbent can be expected to be used in agriculture and horticulture.(3) A superabsorbent resistant to saline solution was prepared from copolymer of partially neutralized MAH,acrylic acid(AA) and AM by solution polymerization using Vc-H₂O₂ as an initiator and both trihydroxymethyl propane glycidol ether(6360) and N,N'-methylenebiacrylamide as crosslinkers.The effects of molar ratio of AA to AM, degree of neutralization of AA,volume of reaction mixture,temperatre of reaction,the amount of crosslinker and initiator on water absorbency were investigated.The results showed that water absorbency of the superabsorbent in 0.9 wt%NaCl solution can reach 77g/g.