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1.
Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a divinyl crosslinker, N,N′-methylenebisacrylamide, have been synthesized by free radical solution and inverse emulsion polymerization. The copolymerization has been carried at different pH values of the monomer mix reaction medium.The copolymers were characterized by their dynamic swelling behavior in deionized water, i.e. the mass of water absorbed by a sample of copolymer was measured vs time. The results were analyzed in terms of the Berens-Hopfenberg non-Fickian equation, leading to a one-only-term relaxation. These kinetics were interpreted by the diffusion-relaxation model and offer quantitative information by diffusivity at 20°C of water in the copolymers. In this investigation, the results have been confirmed within experimental error as the sample of the copolymer is swollen.  相似文献   

2.
The superabsorbent poly(AM-SAS-AA)s were synthesized to improve the water absorption capacities in comparison with the poly(AM-SAS) by an aqueous solution polymerization method from acrylamide (AM), sodium allylsulfonate (SAS), and acrylic acid (AA). The reaction conditions were controlled by varying the AA concentrations and fixing other agent concentrations to obtain the optimal superabsorbent poly(AM-SAS-AA). The poly(AM-SAS-AA) showed maximal absorption capacity at 0.3 mol/L among AA concentrations from 0.053mol/L to 0.4 mol/L. The water absorption capacities of poly(AM-SAS-AA)s prepared at the optimal reaction condition were measured within the temperature ranges from 298.15K to 318.15K. Those experimental data were used to describe the effect factors on absorption capacities and swelling equilibria data among those data were correlated with the swelling models to estimate the interchange energy parameters. Each swelling models combined with group contribution models (UNIFAC, ASOG) was introduced to calculate the swelling equilibria of water(1)/poly(AM-SAS-AA)(2) systems. The swelling behaviors could be described by the estimated parameters, and the calculated values agreed well with the experimental data.  相似文献   

3.
Sorption curves are generated from a mathematical model which includes the influence of the polymer swelling for unsteady-state sorption of a vapor or liquid by a polymer. To investigate the simultaneous effects of the specific volumes of the polymer-penetrant pair and the difference between the final and initial equilibrium concentrations on the sorption curves, statistical experimental design approach is used. Simulation results obtained from the numerical solution of model equations are utilized to estimate the error that would occur if one simply evaluates the diffusion coefficient using the traditional formulas derived from the analytical solution of the sorption equation. An empirical expression is developed that describes the effects of the difference between the final and initial equilibrium concentrations and the specific volumes of the polymer and the penetrant on the magnitude of error in diffusivity associated with the use of one of these traditional formulas so called the initial slope method. The predictive ability of the regression model is tested by performing additional simulations not used in the regression analysis.  相似文献   

4.
Volkan Can  Oguz Okay 《Polymer》2007,48(17):5016-5023
The swelling behavior and the elastic properties of nanocomposite hydrogels have been investigated. The hydrogels were prepared by free-radical polymerization of the monomers acrylamide (AAm), N,N-dimethylacrylamide (DMA), and N-isopropylacrylamide (NIPA) in aqueous clay suspensions at 21 °C. Laponite with a radius of gyration in distilled water of 20 nm was used as clay particles in the hydrogel preparation. The reactions with AAm monomer were carried out in the presence of the chemical crosslinker N,N′-methylenebis(acrylamide) (BAAm). It was found that the volume of nanocomposite hydrogels immersed in water rapidly increases and attains a maximum value after about one day. Surprisingly, further increase in the swelling time results in the deswelling of the gels until they reach a limiting swelling ratio after about 5 days. This unusual swelling behavior is observable only when the clay concentration in the hydrogel is above the overlap threshold c. Swelling measurements combined with the elasticity tests show that the effective crosslink density first decreases, but then increases with increasing time of swelling of the hydrogels. The results were explained in terms of the rearrangements of the highly entangled polymer chains and clay particles during the gel volume change.  相似文献   

5.
    
This article investigates the synthesis of superabsorbent hydrogels (SAHs) based on acrylamide and acrylic acid by solution polymerization in the presence of N,N′-methylenebisacrylamide (NMBA) as a cross-linker and potassium per sulphate as initiator. In this work the acrylamide content was varied in a large range of 30–70% (mole of total monomer) in feed, in order to study its effect on swelling behavior. The results indicate that when acrylamide content present in the hydrogels was increased from 17.23–35.85% (mole of the total monomer); then equilibrium water absorbency also increased from 276–573 (g water/g sample). But when acrylamide content was further increased from 35.85–50.24%, then equilibrium water absorbency abruptly decreased. The equilibrium water absorbency of various copolymeric hydrogels was also investigated in different concentration of saline solutions. The effect of SAHs on growth of seeds of lentil was also studied. The hydrogels were also characterized by fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM); and network parameters such as average molecular weight between cross-links (Mc) and cross-link density (q) were determined to explain the swelling behavior.  相似文献   

6.
A series of novel superabsorbent hydrogel composites, poly(CMC-g-cl-PAam/Zeolite) (ZSAPC) were prepared by in situ graft polymerization using a cellulosic backbone, acrylamide and natural zeolite. The swelling and deswelling behavior of the prepared composites was evaluated and analyzed by different empirical models. The composite with optimum water absorption capacity were impregnated with ZnSO4 in situ during polymerization reaction. Zincated composites showed less water absorption capacity as compared to non-zincated ones. Zinc release behavior of zincated test hydrogel composites was studied in water and soil. All the test compositions exhibited non-Fickian or anomalous transport (0.43 < n < 0.84) and behaved as slow release products.  相似文献   

7.
以腐植酸与丙烯酰胺为原料,采用反向悬浮聚合法制备了一种腐植酸基复合高吸水性树脂聚丙烯酰胺-腐植酸钠(PAM-NaHA),分别研究了交联剂、引发剂用量及聚合温度对树脂吸水率的影响,以及树脂对沙土吸水保水性能的促进作用.结果表明:当n(MBAA)∶n(AM)=0.0005、n(APS)∶n(AM)=0.008、聚合温度为6...  相似文献   

8.
聚丙烯酸钠超强吸水树脂综合应用性能研究   总被引:5,自引:0,他引:5  
水溶液聚合法合成了由山梨醇交联的聚丙烯酸钠超强吸水树脂,对所得产品进行了IR,TG表征.研究了该树脂的溶胀率,溶胀动力学扩散模型,耐酸碱性、耐热、耐寒及耐光等性能.分析了该树脂的溶胶、凝胶质量分数,羧酸根(-COOH)的摩尔分数.测试了不同温度下的溶胀率、保水性能.利用热重法对该树脂的热分解动力学过程进行研究,并计算了热分解动力学参数:活化能Ea,指前因子A,反应熵S^*,反应自由能G,反应焓H.实验结果表明该树脂具有较好的综合应用性能.  相似文献   

9.
A model for the swelling of superabsorbent polymers   总被引:29,自引:0,他引:29  
When dry superabsorbent polymers are immersed in water they swell by two or three orders of magnitude. Both the ultimate degree of absorption and rate of absorption are important in practical applications. Experimentally they depend on the type of polymerisation, e.g. suspension or solution; the monomer composition, e.g. proportions of acrylic acid, sodium acrylate and acrylamide; and on the type of cross-linker, e.g. water or oil-soluble. In this paper relationships between the various parameters are investigated in order to improve understanding and to identify the basic limiting factors. Plots of swelling against time have been found to fit mathematical relationships which are based on spring and dashpot models and are applied in the polymer field to viscoelastic systems. By associating the spring element with resistance to expansion by the absorbent and the dashpot element with resistance to permeation and by relating the behaviour of the elements to the polymerisation system, underlying molecular factors influencing absorption behaviour could be identified. Relationships were also established between the ultimate degree of swelling and the ratio of cross-linker to monomer for the different polymerisation systems.  相似文献   

10.
Marilia Panayiotou 《Polymer》2005,46(18):6777-6785
Temperature-responsive poly(N,N-diethylacrylamide) and poly(N-isopropylacrylamide) hydrogels were synthesised by free radical polymerisation at room temperature with different crosslinker and constant initiator/accelerator concentration. At low crosslinker concentration transparent or translucent gels were obtained, while the gels produced at high crosslinker concentration were opaque. Whereas little difference could be observed between these gels in regard to the temperature of collapse, the swelling/deswelling behaviour showed discrepancies, in that the opaque gels (higher degree of crosslinking) showed a lower swelling ratio, but more efficient water release and more pronounced relative water uptake (reswelling). Low molecular weight additives (potassium salts) had an effect on the on the critical temperature and the swelling ratio; the strength of the observed effect corresponded to the position of the anion in the Hoffmeister series. For most salts the critical temperature was found to decrease (‘salting out’ effect) almost linearly with increasing salt concentration. A linear relationship could be established between the change in critical temperature of the gels and the ‘Viscosity B Coefficient’ of the added anion. Low concentrations of KI showed a ‘salting in’ effect for all investigated gels, while low amounts of KCl showed such an effect only in the case of the poly(N,N-diethylacrylamide) gels. The ‘salting in’ effect was accompanied by an increase in the maximum swelling ratio below the critical temperature. In a cytotoxicity test with Jurkat cells the poly(N-isopropylacrylamide) gels, but less the poly(N,N-diethylacrylamide) gels negatively influenced the morphology, if not the number and viability of the cells, after a contact time of 6 h.  相似文献   

11.
高吸水性聚合物的应用与发展   总被引:18,自引:1,他引:18  
赵华  范瑞生 《中国塑料》1999,13(4):11-16
介绍了高吸水性树脂的生产概况及应用领域,对高吸水性树脂的吸水原理,性能及测定方法进行了论述,并结合目间实际状况对高吸水性对脂的发展提出了建议。  相似文献   

12.
张俊  毛彩红  陈小玲  赵彦生 《塑料工业》2013,41(7):13-16,26
以聚琥珀酰亚胺(PSI)为原料,采用无毒的γ-氨丙基三乙氧基硅烷(KH550)代替有毒的二胺类化合物作为交联剂,在水体系中合成了聚天冬氨酸高吸水性树脂,并探讨了交联剂用量、水解反应的pH值、交联温度和交联时间对高吸水性树脂吸水倍率的影响。采用红外光谱(FTIR)和扫描电镜(SEM)对高吸水性树脂进行表征。结果表明,KH550可以作为聚天冬氨酸高吸水性树脂的交联剂,且采用KH550为交联剂可以实现在水溶液中合成聚天冬氨酸。当KH550的摩尔分数是1.2%、水解反应的pH=10、交联温度为75℃、交联时间为2 h,所得产物在蒸馏水和生理盐水中的吸水倍率分别为455、115 g/g。FTIR分析表明,KH550已接枝到PSI链上,并且形成Si—O—Si结构。SEM结果显示树脂形成一种多孔的结构。  相似文献   

13.
A novel chitosan-g-poly (acrylic acid)/unexpanded vermiculite (CTS-g-PAA/UVMT) superabsorbent composite was prepared by graft polymerization among chitosan (CTS), acrylic acid (AA) and unexpanded vermiculite (UVMT) in aqueous solution. The effect of polymerization variables, including the content of crosslinker, initiator and UVMT, the weight ratio of AA to CTS, the reaction temperature, time and drying method, on water absorbency were studied. The swelling rate of the superabsorbent composite in distilled water was also investigated. The results from FTIR spectra showed that CTS and UVMT participated in graft polymerization reaction with AA. Introducing UVMT into the CTS-g-PAA polymeric network could form a loose and more porous structure by the SEM analysis, and the polymerization reaction is performed on the surface of UVMT micropowders from the results of XRD. The introduced UVMT enhanced the swelling rate and the water absorbency of CTS-g-PAA/UVMT superabsorbent composite.  相似文献   

14.
Vermiculite (VMT) was modified with cetyl trimethylammonium bromide (CTAB). Superabsorbent nanocomposites were prepared by solution polymerization of natural guar gum (GG), partially neutralized acrylic acid (NaA) and organo-vermiculite (CTA+-VMT), ammonium persulfate (APS) as initiator and N,N′-methylene-bis-acrylamide (MBA) as crosslinking agent. FTIR spectra confirmed that NaA had been grafted onto GG and the OH groups of CTA+-VMT participated in the polymerization reaction. The intercalated-VMT was exfoliated during polymerization and uniformly dispersed in the GG-g-PNaA matrix. Swelling tests show that CTA+-VMT improved swelling and swelling rate more remarkably than VMT, and the nanocomposite exhibited distinct kinetic swelling behavior in NaCl and CaCl2 solution. Organo-VMT improved the gel strength of the nanocomposite compared to VMT, and the maximum storage modulus of the nanocomposite reached 658 Pa (γ = 0.5%, ω = 100 rad/s).  相似文献   

15.
金鑫  蔡京荣  韩敏  刘洋 《化学与粘合》2007,29(5):375-377
从提高高吸水性树脂的耐盐性出发,以硝酸铈铵为引发剂,N,N'-亚甲基双丙烯酰胺为交联剂,采用水溶液聚合法,制备了黄原胶接枝丙烯腈耐盐型高吸水性树脂.通过单因素分析法考查了引发剂用量、碱用量、聚合温度、交联剂用量等因素对产物吸水性能的影响.利用红外光谱对产物结构进行了表征.结果表明:黄原胶与丙烯腈发生了接枝聚合反应,所得树脂对蒸馏水的吸收倍率可达1156g.g-1,对0.9%NaCl溶液的吸收倍率可达518g.g-1,是一种耐盐型高吸水性树脂.预期在农业、生理卫生等领域具有较高的应用价值.  相似文献   

16.
Kappa-carrageenan (κC) was modified via graft copolymerization of acrylamide (AAm) using γ-irradiation and followed by alkaline hydrolysis to achieve a novel superabsorbent hydrogel. The effect of grafting variables and alkaline hydrolysis conditions such as κC/AAm compositions and irradiation doses, NaOH concentration, hydrolysis time and temperature were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. Swelling properties and FT-IR of untreated κC-g-PAAm and hydrolyzed κC-g-PAAm (H-κC-g-PAAm) were determined. The swelling capacity of hydrolyzed κC-g-PAAm was about 10 times in distilled water and three times in NaCl solution higher than that for κC-g-PAAm. The swelling of superabsorbing hydrogels was examined in buffer solutions. The swelling capacity of hydrogels was also measured in various salt solutions (LiCl, NaCl, KCl, CaCl2, and FeCl3). Results indicated that the swelling ratios decreased with an increase in the ion radius, valence and ionic strength of the salt solutions. Due to their high swelling ability in salt solutions, the hydrogels may be referred to as ‘anti-salt superabsorbent’ polymers. Thus, the salinity of water treated with H-κC-g-PAAm hydrogels was determined. It was found that the H-κC-g-PAAm hydrogels have a capability to absorb and retain the fresh water from the saline solution. The results obtained suggested the possible used of such prepared superabsorbent in agricultural purposes as a material for sodic soil remediation.  相似文献   

17.
Poly[4,4′-diphenylamine (3,5-di-tert-butyl-4-hydroxy)benzylidene] was synthesized with a dehydrative polycondensation by using H2SO4 as a catalyst. After treatment with DDQ, the polymer was oxidized with PbO2 to generate a stable radical group in the polymer. The colour of the polymer changed from green to dark red upon the oxidation. ESR spectra showed not only a signal with a g value of 2.004, but also a so-called ‘half-field’ signal with a g value of 4.288.  相似文献   

18.
    
pH-sensitive acrylic acid grafted polyvinylalcohol (AAc-g-PVA) hydrogels has been prepared by gamma irradiation. The maximum grafting yield was at monomer concentration 50% and dose 50 kGy. The swelling, network parameters, thermogravimetric analysis, activation energy and scanning electron microscope of the grafted hydrogels were evaluated. Hydrogel demonstrate high swelling at pH 6.8. The deswelling of the swollen gel in Ni2+ and Cu2+ cations solution was explained on the basis of mono-divalent cation exchange. The release of antihistaminic chlorphenamine maleate hydrochloride (CPM) was faster in gastric fluid (SGF) of pH 1.1 than in intestinal fluid (SIF) of pH 6.8.  相似文献   

19.
    
Nickel ions were imprinted in the prepared acrylamide/citric acid P(AAm/CA) hydrogels by using gamma rays. The conditions influencing the preparation of imprinted hydrogels are optimized. The porosity and the characterization of the prepared P(AAm), P(AAm/CA), P(AAm/CA)-M hydrogels was preformed using (TGA) and (SEM). The gel content increases by increasing the monomer concentration and the irradiation dose up to 25 kGy. The swelling (%), rate constant (k), equilibrium ratio (Seq), diffusion constant (n) and the swelling behavior in response to pH value was studied. The Ni2+ imprinted hydrogel can considerably enhance the adsorption capacity and selectivity of the metal ion from wastewater.  相似文献   

20.
The anion influence on the volume changes of polyaniline (PANI) thick films (∼200 μm) during redox switching was studied using voltammetric experiments with simultaneous microscopical observation. The area occupied by the polymer film in the microscope images was measured and used to compute the film volume and its variations. It is found that the electrolyte anion has a definite influence on the film volume changes. When a film equilibrated with perchloric acid is transferred to sulphuric acid, fully reduced and relaxed and afterwards subject to voltammetric cycling, a net volume increase is observed, spanning several potential cycles until a stationary profile is reached. This change is not reversed when the film is transferred back to perchloric medium, and in this electrolyte the response shows a faster evolution. Exchanges with hydrochloric acid show behaviour more similar to HClO4. IR measurements show that anion exchange is complete before the voltammetric cycling is started, indicating that anion ingress/exchange alone is not the only cause for PANI volume changes. The results are interpreted in terms of polymer backbone conformational changes and polymer/anion interactions.  相似文献   

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