| Water superabsorbent (SAP) is a kind of polymers which has high waterabsorption and water-retention properties. It has strong absorbent group, throughwhich it can quickly absorb hundreds and even thousands of times of water based onits weight. It is harmless and tasteless and has characteristics of high waterabsorption capacity, rapid water absorption and high water retention. It has beenwidely used in many fields through the rapid development of recent decades.Compared with the synthetic superabsorbents, superabsorbents prepared withnatural material have the advantages, such as low production cost,environment-friendly property and biodegradability. Therefore they have graduallyattracted extensive attention.This article attempts to prepare corn stalk composite-poly (AM/AA/SSS)superabsorbent by graft copolymerization among corn stalk, acrylamide (AM),acrylic acid (AA) and sodium4-styrenesulfonate (SSS) in aqueous water solution,using ammonium persulfate and sodium bisulfite as redox initiators and N, N’-methylenebisacrylamide (MBA) as crosslinker. Factors influencing water absorptionrate, water absorbency, water retention, and gel strength of the corn stalk-compositesuperabsorbent, such as corn stalk amount, initiator amount, crosslinker amount,neutralization degree of AA and AA/AM mass ratio, were investigated.Morphologies of the corn stalk-composite superabsorbent were characterized byoptical microscope and scanning electrical microscope (SEM). Thermo-stability ofthe corn stalk-composite superabsorbent was characterized by thermogravimetricanalysis (TGA) and differential scanning calorimetry (DSC). Structure of the cornstalk-composite superabsorbent was characterized by Fourier transform infrared spectroscope (FTIR) and X-ray diffraction (XRD). The main research results are asfollows:(1) Corn stalk composite-poly (AM/AA/SSS) superabsorbent, with low cost,environment-friendly property, as well as good water absorbency, water retention,temperature-resistance and gel strength, was prepared by graft-copolymerizationwith AA, AM and SSS in water solution.(2) The optimal technological conditions to preparation the corn stalkcomposite-superabsorbent are as follows:10%corn stalk (based on the totalmonomer mass),0.4wt%crosslinker (based on the total monomer mass),2%initiator (based on the total monomer mass),65%neutralization degree ofAA,AA/AM mass ratio of60:40and15wt%SSS. The corn stalkcomposite-superabsorbent prepared under the optimal technological conditions canreach water absorbency of660g/g within30min with salt absorbency of76g/g.(3) The corn stalk composite-superabsorbent with different amount of cornstalk can reach equilibrium water absorbency within50min. When corn stalkamount is10wt%, water absorbency of the corn stalk composite-superabsorbent canreach217g/g within15min which accounts for62.4%of equilibrium waterabsorbency, as well as291g/g within30min which accounts for83.6%ofequilibrium water absorbency(4) Water absorbency rate, water absorbency, gel strength and water retention ofthe corn stalk composite-superabsorbent increased with increasing corn stalk amount.While water absorbency rate, water absorbency and gel strength of the corn stalkcomposite-superabsorbent decreased obviously with corn stalk amount above10wt%.(5) FTIR spectrum appears the characteristic absorption peaks which can beascribed to corn stalk, AM unit, SSS, unit and AA unit, respectively, demonstratingpreliminarily the structure of corn stalk grafted-poly (AM/SSS/AA) superabsorbent.(6)XRD result indicated that there existed the graft reaction between the starchand monomers, which destroyed the crystalline structure of corn stalk. The preparedcorn stalk composite-superabsorbent had an amorphous structure.(7) Optical microscope showed the sea-island structure of the dried cornstalk-composite superabsorbent and many network-like structure of the water filledcorn stalk-composite superabsorbent.(8) SEM data showed that the discontinuous sheet structures of corn stalksdisappeared and gel aggregates with many large microporous holes and small capillary pores were formed after corn stalk graft modification.(9) TGA and DSC curves of the corn stalk composite-superabsorbent can bedivided into three stages with the good thermo-stability of the corn stalkcomposite-superabsorbent higher than244℃. |
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