| The study of polymer/montmorillonoid superabsorbent composite were mainly in low amount of montmorillonoid when water superabsorbency and retention must be controled in a high level,the reduction of cost was not obvious.In this paper,superabsorbent composite of high amount of acrylate-Ca-bentonite/poly(sodium acrylic) was synthesized through solution polymerization used special process with acrylate-Ca-bentonite (ABT), sodium acrylic and acrylic acid. The preparation process was optimized. The results are as follows:The amount of crosslinker and initiator0.3wt%,1.1wt%of the monomer mass respectively, the total water in the system is340wt%of the monomer mass, the neutralization degree is64%, the amount of ABT is30wt%,the initiator added separate into four times, the pH of alkaline-Ca-bentonite is8.5.The absorbency of the composite is1214g/g in deionized water and67g/g in0.9%salt water in the optimal conditions. At the same time, the water retention was tested in80℃, the result showed that the water retention property of the superabsorbent composite(HABT/PAA) was better compared to that of PAA.The morphology of alkaline-Ca-bentonite, acrylate-Ca-bentonite and the composite were observed by scanning electron microscope(SEM) and transmission electron microscope(TEM). The results showed that alkaline-Ca-bentonite lamelar stacked tightly together,acrylate-Ca-bentonite stacked loosely in baculiform or little lamelar form, in the photogragh of HABT/PAA,acrylate-Ca-bentonite is evenly and disorder dispersed in the composite with the sheets of20nm～30nm thickness when acrylate-Ca-bentonite over400mesh before used. The structure of alkaline-Ca-bentonite, acrylate-Ca-bentonite, HABT/PAA was characterized by XRD. The results indicated that intercalated and/or exfoliated structures between layers were formed during polymerization process,the layer spacing of acrylate-Ca-bentonite was0.23nm wider compare to alkaline-Ca-bentonite,The thermal stability of the composite was characterized by comprehensive thermal analyzer.During the period of the lost of weight, the initial temperature and peak temperature of HABT/PAA(contain15%acrylate-Ca-bentonite) and HABT/PAA(contain30%acrylate-Ca-bentonite) were higher than PAA’s.The results indicated that thermal stability of the composite was better compared to that of polyacrylic acid,and with the improvement of bentonite content, the heat resistance of composite increase.The polymerization regularity indicated that the increasing rate of viscosity was different when initiator added was separated into different times during polymerization,the increasing rate of viscosity decreased when the separated times increased, the comprehensive properties including absorbency and retention are optimal when initiator added was separated into4times.In order to enhanced the saltresistance and gelstrength of HABT/PAA, polyvinyl alkohol(PVA) was adopted to prepare HABT/PAA-PVA semi-interpenetrating polymer network composite, The result indicated that when PVA-124compounded with HABT/PAA, the absorbency of saltwater was increased compare to HABT/PAA. |
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