| Using cornstarch and oxidataed cassava starch as raw materials, cornstarch superabsorbent and high-oxidated cassava starch superabsorbent were prepared by synthesizing grafted starch- acrylic acid- acrylamide(or -acrylic ester) in the clay supspension by solution polymerization for the first time, and another kind of cornstarch superabsorbent was first prepared by reversed phase suspension polymerization. The optimum synthetic processes, absorbing characters and keeping water characters for the three kinds of starch superabsorbents were dicussed. Reversed phase suspension polymerization was compared with solution polymerization. The absorbability of the products were determined, and the best absorbability in deionized water and 0.9% NaCl solution of these new products were as follows: cornstarch superabsorbent: 1819g/g polymer in deionized water and 129g/g polymer in 0.9% NaCl solution; high-oxidated cassava starch superabsorbent: 1359g/g polymer in deionized water and 158g/g polymer in 0.9% NaCl solution; cornstarch superabsorbent prepared by reversed phase suspension polymerization: 1186g/g polymer in deionized water and 113g/g polymer in 0.9% NaCl solution. The absorbability in deionized water and 0.9% NaCl solution of the products were better than those from Boya Technical Tangshan LTD.. The structures of the products were identified by FT-IR. TG-DSC analysis indicated that the products had good thermostability. SEM analysis showed that the products had cavernous samdwich and floccule in the surface, which were in favor of good absorbability and keeping water characters.The synthetic conditions of these new products were researched systematically. The suitable synthetic conditions were as follows:Cornstarch superabsorbent: Cornstarch was Pasted in 80℃ and in 30min. The amounts of cornstarch, bentonite, initiator, crosslinking agent were 5%, 5%, 0.30%, 0.06% respectively, based on the amount of monomers. The amount of acrylamide was 40%, based on the amount of acrylic acid. The neutralization degree of acrylic acid was 90 %. Reaction temperature was 70℃.High-oxidated cassava starch superabsorbent: The suitable oxidated cassava starch was high-oxidated cassava starch. High-oxidated cassava starch was pasted in 90℃. The amounts of high-oxidated cassava starch, bentonite, initiator, crosslinking agent were 10%, 5%, 0.30%, 0.06% respectively, based on the amount of monomers. The amount of acrylamide was 30%, based on acrylic acid. Reaction time was 70℃.Cornstarch superabsorbent prepared by reversed phase suspension polymerization: The volume ratio of cyclohexane, as dispersed phase, to water was 3 :1. The amount of span-60 and tween-80, as dispersant, was 4%, based on the amount of cyclohexane, and their ratio was 2 : 1. The suitable addition order was that the NaOH solution dissolving sodium bisulfite was dropped into reaction system after mixed solution were added into reaction system. The amount of initiator, crosslinking agent, bentonite were 0.20%, 0.03%, 4% respectively, based on the amount of monomers. The amount of acrylamide was 40%, based on acrylic acid. Reaction time was 70℃.Reversed phase suspension polymerization was compared with solution polymerization. The results showed that the absorbability of starch superabsorbents prepared by solution polymerization was better than that prepared by reversed phase suspension, however, the reaction system of reversed phase suspension polymerization, which was without the phenomena of agglutination on the retort, was more stable than that of solution polymerization, and was easier to be controlled. And the products were easier to be processed. Therefore, the reversed phase suspension polymerization should be further developed.The water absorbability of the above products in differend kinds ofsolution, repeating absorbability and the influence of diameter of the partical of the products were discussed. The experiment results showed that inflated behavior could be explained by Flory' inflation theory, but did not a...
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