Synthesis of poly(AA‐co‐AM) superabsorbent composites by reinforcement of halloysite nanotubes

A novel poly(acrylic acid‐co‐acrylamide)/halloysite nanotubes [PAA‐AM/HNTs] superabsorbent composite was synthesized by free radical polymerization with using HNTs as an inorganic additive. The composite was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, and thermogravimetric analysis. The results revealed that HNTs and PAA‐AM were combined well together to form a porous structure with a pore size of about 10 μm, and HNTs were uniformly distributed in the composite. The thermal stability was improved by adding HNTs in the composite. The influences of contents of initiator and halloysite, neutralization degree of AA, and molar ratio of AM to AA on water absorbency were investigated. The water absorbency and the water retention capacity were improved after adding HNTs into PAA‐AM. The composite containing 10% HNTs had the highest water absorbency of 1276 g/g in distilled water. Moreover, PAA‐AM/HNTs composite also had a high swelling rate within 60 min and could maintain 78% initial swelling capability after five reswelled test. The substantial enhancement of swelling properties enables PAA‐AM/HNTs suitable for numerous practical applications. POLYM. COMPOS., 36:229–236, 2015. © 2014 Society of Plastics Engineers     

Study on superabsorbent composite. XX. Effects of cation‐exchanged montmorillonite on swelling properties of superabsorbent composite containing sodium humate

In this work, the effects of different cation‐exchanged montmorillonite on water absorbency of poly(acrylic acid‐co‐acrylamide)/montmorillonite/sodium humate (PAA‐AM/MMT/SH) superabsorbent composite were systematically investigated under the same preparation conditions. The superabsorbents doped with different cation‐exchanged montmorillonite were characterized by Fourier‐transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy technologies. Swelling behaviors of developing superabsorbent composite in various cationic saline solutions (NaCl, CaCl₂, and FeCl₃) were also investigated. The water absorbencies of superabsorbent composite with 20 wt% MMT and 30 wt% SH are 638, 723, 682, and 363 g g⁻¹ in distilled water for incorporating natural Na⁺‐MMT, Li⁺‐exchanged MMT, Ca²⁺‐exchanged MMT, and Al³⁺‐exchanged MMT, respectively. The results showed that the cation‐exchange process had some obvious influences on final water absorbency of superabsorbent composite. NaCl, CaCl₂, and FeCl₃ solutions did not alter the swelling characteristics of the superabsorbent materials at a concentration of less than 0.01 mM, however, a concentration of greater than 0.1 mM caused a collapse in the swelling curves. The excellent swelling‐reswelling‐swelling behavior and lower swelling rate testified that Al³⁺‐exchanged MMT can act as an assistant crosslinker in the polymeric network. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Preparation of starch‐graft‐poly(acrylamide)/attapulgite superabsorbent composite

A novel starch‐graft‐poly(acrylamide)/attapulgite superabsorbent composite was synthesized by graft copolymerization reaction of starch, acrylamide (AM), and attapulgite micropowder using N.N‐methylene‐bisacrylamide (MBA) as a crosslinker and ammonium persulphate (APS) as an initiator in aqueous solution, followed by hydrolysis with sodium hydroxide. The effects on water absorbency, such as amount of crosslinker, initiator, attapulgite, weight ratio of acrylamide to starch in the feed, gelatinization conditions of starch and molar ratio of NaOH to acrylamide, and so forth, were investigated. These superabsorbent composites were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The water absorbencies for these superabsorbent composites in water and saline solution were investigated, and water retention tests were carried out. Results obtained from this study showed that the water absorbency of superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10% exhibit absorption of 1317 g H₂O/g sample and 68 g H₂O/g sample in distilled water and in 0.9 wt % NaCl solution, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1351–1357, 2005     

Utilization of starch and montmorrilonite for the preparation of superabsorbent nanocomposite

Starch and montmorrilonite (MMT) were used as raw materials for synthesizing starch‐graft‐poly[acrylamide (AM)–acrylic acid (AA)]/MMT superabsorbent nanocomposite by graft and intercalation copolymerization reaction of starch, AM, and AA in the presence of organic MMT micropowder in aqueous solution. Major factors affecting water absorbency such as weight ratio of monomers to starch, weight ratio of AM to AA, neutralization degree of AA, amount of crosslinker, initiator, and MMT were investigated. The superabsorbent nanocomposite synthesized under optimal synthesis conditions exhibits absorption of 1120 g H₂O/g sample and 128 g H₂O/g sample in deionized water and in 0.9 wt % NaCl solution, respectively. IR spectra showed that the graft copolymerization between  OH groups on MMT and monomers took place during the reaction, and that crystal interlayer was pulled open in the superabsorbent nanocomposite. X‐ray diffraction analysis showed that the crystal interlayer of MMT was pulled open to 2.73 nm, and thus formed nanometer exfoliation composite material. Thermogravimetric analysis showed that starch‐graft‐poly (AM–AA) superabsorbent nanocomposite (8 wt % MMT) has good thermal stability. This superabsorbent nanocomposite with excellent water absorbency and water retention, being biodegradable in nature, economical and environment friendly, could be especially useful in industry, agricultural, and horticultural applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and slow‐release property of a poly(acrylic acid)/attapulgite/sodium humate superabsorbent composite

A novel poly(acrylic acid)/attapulgite (APT)/sodium humate (SH) superabsorbent composite was synthesized through the graft copolymerization reaction of acrylic acid on APT micropowder and SH with N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in an aqueous solution. Various effects on the water absorbency, including the amounts of the crosslinker, initiator, APT, and SH, were investigated. The superabsorbent composite was characterized with Fourier transform infrared spectroscopy and scanning electron microscopy. The superabsorbent composite synthesized under optimal synthesis conditions with an APT concentration of 20% and an SH concentration of 20% exhibited absorption of 583 g of H₂O/g of sample and 63 g of H₂O/g of sample in distilled water and in a 0.9 wt % NaCl solution, respectively. The slow‐release property of SH from the superabsorbent composite into water was measured, and a test of the water retention of the superabsorbent composite in soil was also carried out experimentally with and without the superabsorbent composite. The results showed that the superabsorbent composite had not only good water retention but also an additional slow‐release property of SH. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 37–45, 2007     

Swelling study of superabsorbent PAA‐co‐PAM/clay nanohydrogel

A series of superabsorbent composites were prepared from acrylic acid (AA), acrylamide (AM), and Cloisite® 30B by aqueous solution polymerization technique using ammonium peroxodisulfate (APS) as initiator. The interaction of the organically modified nanoclay with PAA‐co‐PAM copolymer was verified by FTIR, whereas the morphology of the composite was studied by Scanning Electron Microscopy (SEM). The water absorbency in deionized water and saline water of the synthesized nanohydrogels was measured by calculating their percentage swelling ratio. The effects of copolymerization, monomer ratio, clay content, and temperature on the water absorbency were studied. The results indicated a considerable increase in swelling ratio by proper monomer proportion and incorporation of optimum clay percentage into the copolymer matrix. It was found that the nanohydrogel acquired highest water absorbency with 2% clay loading. The reswelling ability and water retention capacity of the PAA‐co‐PAM hydrogel and PAA‐co‐PAM/clay nanohydrogel were also measured. The water absorbency was found to increase after each reswelling for which it may be useful as recyclable superabsorbent material. The results of water retention capacity of the nanohydrogel were also encouraging and find application in agriculture, especially in drought‐prone areas. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of potassium humate on the swelling properties of a poly(acrylic acid‐co‐acrylamide)/ potassium humate superabsorbent composite

A novel superabsorbent composite, poly(acrylic acid‐co‐acrylamide)/potassium humate (PAA‐AM/KHA), was prepared by aqueous solution polymerization from acrylic acid, acrylamide, and potassium humate (KHA) with N,N′‐methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator. The effects of incorporated KHA on the water absorbency, swelling rate, and reswelling capability were investigated. The swelling property of PAA‐AM/KHA in various saline solutions was studied systematically. The results show that the comprehensive properties and especially salt‐resistant ability of PAA‐AM/KHA were enhanced. There was a linear relationship between the saturated water absorbency and the minus square root of the ionic strength of the external medium, and the water absorbency of PAA‐AM/KHA in various salt solutions had the following order: NH₄Cl_(aq) = KCl_(aq) = NaCl_(aq) > MgCl_2(aq) > CaCl_2(aq) > AlCl_3(aq) > FeCl_3(aq). Moreover, the polymeric net structure of PAA‐AM/KHA was examined with respect to that of poly(acrylic acid‐co‐acrylamide). The results indicate that the polymeric net of PAA‐AM/KHA was improved by the introduction of a moderate amount of KHA into the superabsorbent composite and made more suitable for agriculture and horticulture applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and water absorbency of a novel poly(acrylate‐co‐acrylamide)/vermiculite superabsorbent composite

A novel poly(acrylate‐co‐acrylamide)/expanded vermiculite (EVMT) superabsorbent composite was synthesized by aqueous solution polymerization method. The water absorbency of the superabsorbent composite still reaches 850 g/g when 50 wt % EVMT is added, which is significant in decreasing the production cost of the superabsorbent composites. By controlling the molar ratio of acrylic acid monomer and acrylamide monomer, and neutralization degree of acrylic acid, the hydrophilic groups on the composite can be adjusted, and it is found that the collaborative absorbent effect of ? CONH₂, ? COOK, and ? COOH groups is superior to that of single ? CONH₂, ? COOK, or ? COOH group. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 735–739, 2007     

Waste polystyrene foam‐graft‐acrylic acid/montmorillonite superabsorbent nanocomposite

A novel superabsorbent nanocomposite based on partially neutralized acrylic acid, waste polystyrene foam, and sodium type montmorillonite (Na‐MMT) powder was synthesized through emulsion polymerization using N, N′‐methylenebisacrylamide as a crosslinker, 2,2′‐azo‐bisiso‐butyronitrile, ammonium persulfate, and sodium sulfite as mixed redox initiators. The effects of such factors as amount of Na‐MMT, crosslinker, initiator, and neutralization degree on water absorbency of the superabsorbent were investigated. The composites were characterized by Fourier transform infrared spectroscope, X‐ray diffraction, thermo gravimetric analysis, and scanning electron microscope. The results show that acrylic acid monomer successfully grafted onto the polystyrene chain, the layers of Na‐MMT were exfoliated and dispersed in the composite at nano size after copolymerization. The introduction of waste polystyrene foam in the composite increased the water absorbency rate. The addition of Na‐MMT not only enhanced the thermal stability of the composites but also increased its water absorbency, and the optimal water absorbencies of distilled water and saline water (w_NaCl = 0.9%) of the nanocomposites were more than 1180 g H₂O/g and 72.6 g H₂O/g, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2341–2349, 2007     

Studies on poly(acrylic acid)/attapulgite superabsorbent composite. I. Synthesis and characterization

A novel poly(acrylic acid)/attapulgite superabsorbent composite was synthesized by graft copolymerization reaction of acrylic acid (AA) on attapulgite micropowder using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator in aqueous solution. The effects on water absorbency of such factors as reaction temperature, initial monomer concentration, degree of neutralization of AA, amount of crosslinker, initiator, and attapulgite were investigated. These crosslinked superabsorbent composites were characterized by thermogravimetetric analysis and scanning electron microscopy. The graft copolymerization reaction of AA on attapulgite micropowder was characterized by FTIR. The water absorbencies for these superabsorbent composites in water and saline solutions were investigated and water‐retention tests were carried out. Results obtained from this study show that the water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10% exhibited an absorption of 1017 g H₂O/g sample and 77 g H₂O/g sample in distilled water and in 0.9 wt % NaCl solution, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1596–1603, 2004     

Synthesis and properties of carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide) as a novel cellulose‐based superabsorbent

A new cellulose‐based superabsorbent polymer, carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide), was prepared by the free‐radical grafting solution polymerization of acrylic acid (AA) and acrylamide (AM) monomers onto carboxymethyl cellulose (CMC) in the presence of N,N′‐methylenebisacrylamide as a crosslinker with a redox couple of potassium persulfate and sodium metabisulfite as an initiator. The influences of reaction variables such as the initiator content, crosslinker content, bath temperature, molar ratio of AA to AM, and weight ratio of the monomers to CMC on the water absorbency of the carboxymethylcellulose‐graft‐poly(acrylic acid‐co‐acrylamide) copolymer were investigated. The copolymer's structures were characterized with Fourier transform infrared spectroscopy. The optimum reaction conditions were obtained as follows: the bath temperature was 50°C; the molar ratio of AA to AM was 3 : 1; the mass ratio of the monomers to CMC was 4 : 1; and the weight percentages of the crosslinker and initiator with respect to the monomers were 0.75 and 1%, respectively. The maximum water absorbency of the optimized product was 920 g/g for distilled water and 85 g/g for a 0.9 wt % aqueous NaCl solution. In addition, the superabsorbent possessed good water retention and salt resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1382–1388, 2007     

Improving properties of superabsorbent composite induced by using alkaline protease hydrolyzed‐sericin (APh‐sericin)

A series of superabsorbent polymer composites based on sericin hydrolyzed with alkaline protease (AP) were prepared by grafting with acrylic acid (AA) and acrylamide (AM). The properties of the superabsorbent polymers (SAP) by using hydrolyzed sericin with different amount of alkaline protease (nAPh‐sericin) were compared. It was found that the polymer prepared from 5APh‐sericin (the mass ratio of AP to sericin was 5.0 mg g⁻¹) showed the highest graft percentage and water absorbency, this phenomenon may be attributed to the change of molecular weight of resulting sericin molecules. The molecular structure of the grafted polymers was proved by thermal gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) measurements. Comparing with PAA‐AM (poly AA‐co‐AM) and 0APh‐sericin/PAA‐AM polymer, 5APh‐sericin/PAA‐AM polymer had the most excellent water retention capacity and enzyme degradability. The morphological features of the polymers with different drying methods were evidenced by SEM images. The water absorbencies of 5APh‐sericin/PAA‐AM polymer prepared with freeze‐drying were 896 g g⁻¹ in deionized water, 424 g g⁻¹ in tap water, and 83 g g⁻¹ in 0.9 wt% aqueous NaCl solution. POLYM. COMPOS., 35:509–515, 2014. © 2013 Society of Plastics Engineers     

Synthesis,characterization and swelling behaviors of hydroxyethyl cellulose‐g‐poly(acrylic acid)/attapulgite superabsorbent composite

In this work, a series of novel hydroxyethyl cellulose‐ g‐poly(acrylic acid)/attapulgite (HEC‐g‐PAA/APT) superabsorbent composites were prepared through the graft polymerization of hydroxyethyl cellulose (HEC), partially neutralized acrylic acid (AA), and attapulgite (APT) in aqueous solution, and the composites were characterized by means of Fourier‐transform spectroscopy, scanning electron microscopy, and transmission electronmicroscopy. The effects of polymerization variables including concentrations of the initiator and crosslinker and APT content on water absorbency were studied, and the swelling properties in various pH solutions as well as the swelling kinetics in various saline solutions were also systematically evaluated. Results showed that the introduction of 5 wt% APT into HEC‐g‐PAA polymeric network could improve both water absorbency and water absorption rate of the superabsorbent composites. In addition, the superabsorbent composites retained high water absorbency over a wide pH range of 4–10, and the swelling kinetics of the superabsorbent composites in CaCl₂ and FeCl₃ solutions exhibited a remarkable overshooting phenomenon. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Synthesis,swelling behaviors,and slow‐release characteristics of a guar gum‐g‐poly(sodium acrylate)/sodium humate superabsorbent

Superabsorbents used in agricultural and ecological projects with low‐cost, slow‐release fertilizers and environmentally friendly characteristics have been extensively studied. The use of a natural polymer as the matrix and then further polymerization with some functional material has become the preferred method. In this work, with natural guar gum (GG), partially neutralized acrylic acid, and sodium humate (SH) as the raw materials, ammonium persulfate as the initiator, and N,N′‐methylenebisacrylamide (MBA) as the crosslinker, GG‐g‐poly(sodium acrylate) (PNaA)/SH superabsorbents were synthesized through a solution polymerization reaction and were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The effects of the SH content and MBA concentration on the water absorbency were investigated. The results showed that the introduction of SH into the GG‐g‐PNaA system could improve the water absorbency, swelling rate, pH‐resistant property, and reswelling capability, and the superabsorbent containing 15 wt % SH had the highest water absorbency of 532 g/g of sample in distilled water and 62 g/g of sample in a 0.9 wt % NaCl solution. The slow release in water and water retention in sandy soil tests revealed that the superabsorbent could act as a fertilizer as well as an effective water‐saving material for agricultural applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Utilization of plant ash for the fabrication of novel superabsorbent composites with potassium‐release characteristics

Design and synthesis of the agricultural and ecological superabsorbent materials with cost‐efficient and fertilizer‐release characteristics has recently attracted considerable interests. In this work, the novel poly(sodium‐potassium acrylate‐co‐acrylamide)/plant ash (PNa‐KA‐co‐AM/PA) superabsorbent composites with potassium‐release characteristics were prepared using partially neutralized acrylic acid (Na‐KA), acrylamide (AM), and plant ash (PA) as raw materials, ammonium persulfate (APS) as the initiator, and N,N′‐methylenebisacrylamide (MBA) as the crosslinker. The structure, morphologies, and thermal stability of the composites were characterized by Fourier transform infrared spectrophotometer, scanning electron microscopy, and TGA techniques, respectively. The effects of MBA concentration and PA content on water absorbency were studied, and the swelling properties of the composites in saline solutions and various pHs solution as well as their potassium‐release capabilities were also evaluated. Results indicate that the composites exhibit better thermal stability, salt‐resistant performance, pH‐stability, and potassium‐release properties, and can act as a fertilizer and an effective water‐saving material for agricultural and ecological application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on superabsorbent composite. XV. Effects of ion‐exchanged attapulgite on water absorbency of superabsorbent composites

A series of superabsorbent composite, polyacrylamide/attapulgite, from acrylamide (AM) and ion‐exchanged attapulgite (APT) was prepared by aqueous polymerization, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The effects of ion‐exchanged APT on water absorbency of superabsorbent composites in distilled water and in 0.9 wt% NaCl solution were studied. The result indicates that higher cation‐exchange capacity (CEC) and lower specific surface area (SSA) of APT treated with various anions are of benefit for improving water absorbency in distilled water. The effects of AlCl₃ solution concentration and Al³⁺‐exchanged APT content on water absorbency of the composite were also investigated. The concentration of AlCl₃ solution has a great influence on water absorbency of the superabsorbent composite. Al³⁺‐exchange of APT could also enhance reswelling ability of the corresponding composite, which indicates that Al³⁺‐exchange of APT could improve gel strength and gives a direct evidence for its acting as an inorganic assistant crosslinker in the polymeric network. POLYM. COMPOS., 28:208–213, 2007. © 2007 Society of Plastics Engineers     

Polyacrylate/(carboxymethylcellulose modified montmorillonite) superabsorbent nanocomposite: Preparation and water absorbency

Montmorillonite (MMT) was modified with carboxymethylcellulose (CMC). The X‐ray diffraction (XRD) and FTIR analyses showed that the CMC chains had intercalated into the MMT sheets, and the strong chemical interaction between the ether bonds from CMC and Si? O bonds from MMT was the driving force for intercalation. Polyacrylate (PAA)/modified MMT superabsorbent nanocomposites were fabricated by effectively dispersing the modified MMT in acrylic acid solution and polymerizing the acid. The superabsorbent composites were characterized by XRD, TEM, and FTIR. The influence of modified MMT, weight ratio of CMC to MMT, and modified MMT content in the nanocomposites on the water absorbency was investigated. Results showed that the introduction of pure MMT could decrease the water absorbency of the gel, but adding modified MMT could not only effectively increase the water absorbency of the gel, but also improve its water retention ability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on poly(acrylic acid)/attapulgite superabsorbent composites. II. Swelling behaviors of superabsorbent composites in saline solutions and hydrophilic solvent–water mixtures

The effect of the attapulgite content on the swelling for a series of poly(acrylic acid)/attapulgite superabsorbent composites in water was studied. The effects of the temperature and pH values on the water absorbency of the superabsorbent composites were investigated. The swelling behavior of the superabsorbent composites in various saline solutions was also investigated. The water absorbency in various salt solutions decreased with an increase in the ionic strength of the solutions. At a high ionic strength (>1 × 10^?3M), the water absorbency in monovalent cationic solutions was higher than that in multivalent cation solutions. This dramatic reduction of the water absorbency in multivalent cationic solutions of high ionic strength may have been due to the complexing ability of the carboxylate groups inducing the formation of intramolecular and intermolecular complexes, which resulted in an increased crosslink density of the network. The swelling behavior of the superabsorbent composites in mixtures of water and hydrophilic solvents, including methanol, acetone, ethanol, and dimethyl sulfoxide (DMSO), was also investigated. The water absorbency decreased with an increase in the concentration of any of the four organic solvents, and two transitions were observed in the superabsorbent composite/hydrophilic solvent–water mixture systems. The main transition for the four hydrophilic solvent–water mixtures was a collapse of the swollen gel (at 50–80% methanol, 30–80% acetone, 50–80% ethanol, and 50–80% DMSO). For the methanol–water system, the magnitudes of the first and second transitions for the poly(acrylic acid)/attapulgite superabsorbent composites containing lower proportions of attapulgite were larger than those for the superabsorbent composites with higher attapulgite contents. The effect of the mixture temperature on the water absorbency of the superabsorbent composites in 10 min was also reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1869–1876, 2004     

Superabsorbent composite. XIII. Effects of Al3+‐attapulgite on hydrogel strength and swelling behaviors of poly(acrylic acid)/Al3+‐attapulgite superabsorbent composites

Al³⁺‐attapulgite (Al³⁺‐APT) was prepared by treating attapulgite (APT) with AlCl₃ aqueous solution of various concentrations. The poly(acrylic acid)/Al³⁺‐attapulgite (PAA/Al³⁺‐APT) superabsorbent composite was prepared by reaction of partly neutralized acrylic acid, and Al³⁺‐APT in aqueous solution using N, N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The surface morphology of the composite was investigated by SEM, and the Al³⁺‐APT composite generated a relatively planar surface comparing the nature APT. The effects of Al³⁺‐APT on hydrogel strength and swelling behaviors, such as equilibrium water absorbency, swelling rate, and reswelling capability, of the superabsorbent composites were also studied. The hydrogel strength and reswelling capability were improved, however, the equilibrium water absorbency and swelling rate decreased with increasing AlCl₃ solution concentration. The equilibrium water absorbency firstly increased, and then decreased with increasing Al³⁺‐APT content. The results indicate that Al³⁺‐APT acts as an assistant crosslinker in the polymeric network, which has great influences on hydrogel strength and swelling behaviors of the PAA/Al³⁺‐APT superabsorbent composites. POLYM. ENG. SCI., 47:619–624, 2007. © 2007 Society of Plastics Engineers.     

Preparation of chitosan‐g‐poly(acrylamide)/montmorillonite superabsorbent polymer composites: Studies on swelling,thermal, and antibacterial properties

Superabsorbent composites based on chitosan‐g‐poly(acrylamide) and montorillonite (CTS‐g‐PAAm/MMT) were synthesized through in situ radical polymerization by grafting of crosslinked acrylamide onto chitosan backbone in presence of MMT at different contents. The formation of the grafted network was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetery (DSC). The obtained porous structure was observed by scanning electron microscope (SEM). The presence of clay and its interaction with chitosan‐g‐poly(acrylamide) (CTS‐g‐PAAm) matrix was evidenced by ATR‐FTIR analysis. The morphology was investigated by both X‐ray diffraction (XRD) and SEM analyses. It was suggested the formation of mostly exfoliated structures with more porous structures. Besides, the thermal stability of these composites, observed by TGA analysis, was slightly affected by the clay loading as compared to the matrix. These hydrogel composites were also hydrolyzed to achieve anionic hydrogels with ampholytic properties. Swelling behaviors were examined in doubly distilled water, 0.9 wt % NaCl solution and buffer solutions. The water absorbency of all superabsorbent composites was enhanced by adding clay, where the maximum was reached at 5 wt % of MMT. Their hydrolysis has not only greatly optimized their absorption capacity but also improved their swelling rate and salt‐resistant ability. The hydrolyzed superabsorbent showed better pH‐sensitivity than the unhydrolyzed counterparts. The results of the antibacterial activity of these superabsorbents composites against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), assayed by the inhibitory zone tests, have showed moderate inhibition of the bacteria growth. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39747.