Synthesis And Properties Of Super Absorbent Poly(Acrylic Acid-acrylamide)

With the depletion of fresh water resources and the problem of drought-prone, water saving and retaining has become one of the most important problem. A functional polymer material, which is called super absorbent polymer or aquasorb, can play a special role for its particular water absorbency and retention characteristics in agriculture industry, forestry and gardening, desert governance, etc. Especially, acrylic super-absorbent polymers have rich raw materials, low cost, long life and other advantages, which are widely studied. But its application is limited for its poor salt resistance and low water absorbency ratio. Therefore, preparation, performance analysis and preliminary application technology of acrylic super absorbent polymer were systematically researched in this work.In this work, poly (acrylate-acrylamide)(PAA-AM) was prepared with acrylic acid (AA) and acrylamide (AM) as monomers, through inverse suspension polymerization, and its performanceswere studied. The results show that PAA-AM has high water absorbency, good salt resistance, excellent performance of soil retention water and fertilizer, etc. The main work and results is provided as the following:PAA-AM was prepared with cyclohexane as a solvent, acrylic acid (AA) and acrylamide(AM) as monomers, N, N’-methylene double acryl amide (NMBA) as a cross-linker, potassium persulfate (KPS) as aninitiator, Span-80as a dispersant, through inverse suspension polymerization. The L25(56) orthogonal experiment was used to study optimal process conditions, with water absorbency in distilled water and0.9%NaCl solution as assessment criteria.The water absorbency of PAA-AM in salt solution of different anion and cation strength and different pH values was studied. Repeat water absorbency was investigated.Influences of temperature, pressure, and different soil textures on the water retention properties of PAA-AM were discussed. Retention function of PAA-AM to N、 P、K fertilizer the soil was studied through leaching test. The structure, Thermal performance and morphology were analyzed using FT-IR, DSC-TGA, NMR and microscope, respectively.The results show that the order of factors from primary to secondary influenced the water absorbency of PAA-AM is the follows:cross-linker> reaction temperature> initiator> oil-water ratio> neutralization degree> monomer ratio. The optimal preparation condition was obtained through inverse suspension polymerization. It is as the following:neutralization degree of75%, monomer ratio of3:1, cross-linker and initiator of0.04%and0.7%respectively, oil-water ratio of3:1, reaction temperature of70℃. The sample of the optimal preparation conditions in distilled water and0.9%NaCl solution water absorbency ratio is1282g/g and109g/g respectively, which is obviously better than322g/g and40g/g of the SNF super absorbent polymers. It shows good salt resistance and water absorbency.The experimental results show that:(1) Alkaline conditions is less than acidic to influence of PAA-AM water absorbency, and the optimum condition of used in environment of acid and alkali is pH value between6to8.(2) PAA-AM has good water retention at room temperature, especially when the pressure is1.2KPa; its water retention rate is still90%.(3) PAA-AM water absorbency has a big effect on salt solution of different anion and cation strength and valence state. The sequence of influence to ionic of different valence state is trivalence> bivalence> monovalence, and water absorbency decreases with increasing ionic strength.(4) PAA-AM is able to obviously improve water absorbency ratio and retention performance of soil, especially sandy soil.(5) PAA-AM plays an obviously role to N、P、K fertilizer of soil, and it is able to restrain loss of N、P、K fertilizer44.6%、16.2%、22.4%, respectively. In short, PAA-AM has high water absorbency, good salt resistance, excellent performance of soil retention water and fertilizer, which can meet the demand in in agriculture industry, forestry and gardening, desert governance, etc.The novelties of the work are mainly focused on the following aspects:(1) To simplify the technological process, to shorten the production cycle——only1.5hours, and samples could be dried at the atmosphere and80℃, which may both save cost and reduce energy consumption;(2) Water absorbency ratio of PAA-AM at distilled water and0.9%NaCl solution is1282g/g,109g/g, respectively, and PAA-AM compares with SNF, which has good water absorbency and salt resistance;(3) Applying PAA-AM can significantly reduce the loss of N, P and K fertilizer in soil and improve the utilization rate of fertilizer, and can also save N, P, K are44.6%,16.2%,22.4%, respectively.