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 of poly(acrylic acid)/sodium humate superabsorbent composite for agricultural use

A novel poly (acrylic acid)/sodium humate superabsorbent composite was synthesized by graft copolymerization reaction of acrylic acid (AA) on sodium humate micropowder using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and potassium peroxydisulfate (KPS) as an initiator in aqueous solution. The effects on water absorbency of factors such as reaction temperature, initial monomer concentration, and degree of neutralization of AA, amount of crosslinker, initiator, and sodium humate were investigated. The superabsorbent composite was characterized by scanning electron microscopy, and the graft copolymerization reaction of AA on sodium humate micropowder was characterized by IR spectroscopy. Results obtained from this study show that the water absorbency of the superabsorbent composite synthesized under optimal conditions for synthesis with a sodium humate content of 5.3% exhibited absorption of 684 g H₂O/g sample in distilled water. Water‐retention in soil is enhanced by the use of the superabsorbent composite. The effect of superabsorbent composite on the growth of corn is reported. The superabsorbent composite may be of use as water management materials for agriculture purposes in desert and drought‐prone areas. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5137–5143, 2006     

Study on superabsorbent composites. XVIII. Preparation,characterization, and property evaluation of poly(acrylic acid‐co‐acrylamide)/organomontmorillonite/sodium humate superabsorbent composites

A series of novel multifunctional poly (acrylic acid‐co‐acrylamide) (PAA‐AM)/organomontmorillonite (O‐MMT)/sodium humate (SH) superabsorbent composites were synthesized by the graft copolymerization reaction of partially neutralized acrylic acid and acrylamide on O‐MMT micropowder and SH with N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in an aqueous solution. The superabsorbent composites were characterized by means of Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The effect of the relative weight ratio of SH to O‐MMT on the water absorbency was studied, and the results indicated that the best water absorbency of 591 g/g in distilled water was obtained when an O‐MMT content of 20 wt % and an SH content of 30 wt % were incorporated. The superabsorbent composite possessed a good capacity for water retention; even after 30 days, 24.4 wt % of water could still be saved by the sand soil containing 1.0 wt % superabsorbent composite. The results from this study show that the water absorbency of a superabsorbent composite is improved by the simultaneous introduction of O‐MMT and SH into a PAA‐AM network in comparison with the incorporation of only O‐MMT or SH. Also, in comparison with PAA‐AM/MMT/SH, an appropriate amount of O‐MMT can benefit the developed composites with respect to their water absorbency, salt resistance, and capacity for water retention in sand soil. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

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     

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 and properties of a slow release NP compound fertilizer with superabsorbent and moisture preservation

A slow‐release NP compound fertilizer with superabsorbent and moisture preservation was prepared by carboxyl methyl starch, acrylic acid, ammonia, urea, diammonium phosphate, and so on. The effects of the amount of initiator, crosslinker, and the degree of neutralization of acrylic acid on water absorbency were investigated and optimized. The product was characterized by FTIR, ICP, and element analysis, and the results showed that the product contained 22.6% nitrogen element and 7.2% phosphor (shown by P₂O₅) element. Its water absorbency was about 85 (g · g^?1) times its own weight in tap water. We also investigated the water retention property of the product and the slow release behavior of N and P in the product. The results showed that the product had a good water retention capacity and slow release property. The mechanism of the release of N and P in water was also investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2132–2138, 2005     

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     

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     

Preparation of superabsorbent slow release nitrogen fertilizer by inverse suspension polymerization

A superabsorbent, slow release nitrogen fertilizer (SSRNF) was prepared by inverse suspension polymerization of partially neutralized acrylic acid using N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of urea. The polymer was characterized using infrared spectral analysis, and network structural parameters such as molecular weight between crosslinks (M_c) and crosslink density (q) were calculated. The effects of reaction conditions, such as reaction time, reaction temperature, initiator, crosslinker and the degree of neutralization of acrylic acid, on water absorbency were investigated. The nitrogen content of SSRNF synthesized under optimal conditions was 22.7%, and the water absorbencies were about 965 g g^?1 in distilled water and 185 g g^?1 in tap water. The nitrogen slow release behaviors of the SSRNF in water and water retention capacity of soil with the SSRNF were also investigated. A possible slow release mechanism was proposed and the release rate constant K and the diffusion coefficient D of urea in the hydrogel was calculated. The results showed that the product not only had good slow release properties but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. Therefore, the SSRNF is a multifunctional water managing material, which would find application in agriculture and horticulture, especially in drought‐prone areas where the availability of water is limited. Copyright © 2006 Society of Chemical Industry     

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     

Granular urea‐formaldehyde slow‐release fertilizer with superabsorbent and moisture preservation

To improve the utilization of fertilizer and water resource at the same time, a new type of slow‐release fertilizer with superabsorbent and moisture preservation was developed, with the combination of slow‐release technique and superabsorbent polymers. The coatings were formed by the inverse phase polymerization technique. The element analysis results showed that the product contained 22.58% nitrogen element, and the water absorbency of the product was 94 times its own weight if it was allowed to swell in tap water at room temperature for 2 h. The results of the slow‐release behavior of N and the water absorbency and retention properties in soil showed that the product not only had good slow‐release property but also had excellent water absorbency and water retention capacity, which was a significant advantage over the normal slow‐release or controlled‐release fertilizers. The effects of the amount of initiator, crosslinker, reaction time, and the degree of neutralization of acrylic acid on water absorbency were investigated and optimized. At the same, a rather new and simple method was used to make homogeneous urea‐formaldehyde granules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3230–3235, 2006     

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     

Study on superabsorbent composite. VIII. Effects of acid‐ and heat‐activated attapulgite on water absorbency of polyacrylamide/attapulgite

A novel superabsorbent composite, polyacrylamide/attapulgite, from acrylamide (AM) and attapulgite (APT), was prepared by free‐radical polymerization, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The effects of hydrochloric acid (HCl) concentration, acidification time, and acidification temperature while acidifying APT and temperature and APT heat‐activation on water absorbency of the superabsorbent composite in distilled water and in 0.9 wt % NaCl solution were studied. The water absorbency first decreases with increasing the HCl concentration while acidifying APT, and then increases with further increasing the HCl concentration. Prolongation of acidification time is of benefit to the increase of water absorbency. At a given HCl concentration, water absorbency for the composite increases with increasing acidification temperature. An important increase in water absorbency was observed after incorporating heat‐activated APT into the polymeric network, reaching a maximum of 1964 g g^?1 with the APT heat‐activated at 400°C. Acid‐ and heat‐activation can influence chemical composition, crystalline structure, cation exchange capacity (CEC), and specific surface area of APT according XRF, XRD, FTIR analysis, and physicochemical properties test, and then on water absorbency of corresponding PAM/APT superabsorbent composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2419–2424, 2007     

Synthesis and properties of a poly(acrylic acid)/montmorillonite superabsorbent nanocomposite

A novel superabsorbent nanocomposite was synthesized through the intercalation polymerization of partially neutralized acrylic acid and a sodium‐type montmorillonite powder with N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate and sodium sulfite as a type of mixed redox initiator. The effects of such factors as the amounts of the sodium‐type montmorillonite, crosslinker, and initiator and neutralization degree on the water absorbency of the nanocomposite were investigated. The structure and micrographs of the superabsorbent were characterized with Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. The results showed that the acrylic acid monomer was successfully intercalated into the montmorillonite layers and banded together with them. The montmorillonite layers were exfoliated and basically dispersed in the composite on a nanoscale after the polymerization. The water absorbency of the nanocomposite was much higher than that of pure poly(acrylic acid). The optimum absorbency of the nanocomposite in distilled water and saline water (NaCl concentration = 0.9%) was 1201 and 83 g/g, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5725–5730, 2006     

Controlled release NPK compound fertilizer with the function of water retention

Controlled release nitrogen, phosphorus and potassium (CRNPK) compound fertilizer with the function of water retention was prepared, which possessed the core/shell structure. Its core was urea formaldehyde (UF) and polyphosphate potassium (PAK) fertilizer, and the shell was P(acrylic acid-co-acrylamide)/kaolin (P(AA-co-AM)/kaolin) superabsorbent composite. Analysis results showed that the N, P and K contents were 11.3, 21.1 (shown by P₂O₅) and 8.6 (shown by K₂O) wt%, respectively. The synthesis conditions of inversion suspension polymerization were studied systematically. The water absorbency of the product was 91 g/g in tap water. The swelling rate, slow release and water retention properties of CRNPK were also investigated. Additionally, the effect of temperature on the nutrients release behaviors was studied. The results showed that the product had high initial swelling rate, and the product not only had a good slow release property but also excellent water retention ability, which could effectively improve the utilization of fertilizer and water resource at the same time.     

Synthesis and characterization of a salt‐resisting superabsorbent based on poly(acrylic acid) with sodium tungstate as a crosslinker

A novel salt‐resistant superabsorbent polymer was synthesized by solution polymerization from the monomer acrylic acid (AA) with potassium persulfate as the initiator. Sodium tungstate was first employed as a crosslinker in the preparation to achieve a better crosslinked polymer (WPAA). In addition to the xerogel WPAA, sodium hydroxide and tris(2‐hydroxyethyl)amine (TEA) were introduced for the preparation of WPAA–sodium and WPAA–TEA hydrogels, respectively. The effect on the water absorbency of factors such as the reaction temperature, degree of neutralization of AA, and amounts of the crosslinker sodium tungstate and the initiator were investigated. The crosslinked xerogels were characterized with infrared spectroscopy. These crosslinked superabsorbent composites with sodium tungstate were characterized with thermogravimetric analysis and scanning electron microscopy. The water absorbencies of these superabsorbent composites in water and saline solutions were investigated. Results obtained from this study showed that under the same synthesis conditions, in comparison with superabsorbent composites with an aluminum salt as a crosslinker and styrene as a graft copolymer, the salt resistance of the superabsorbent composite synthesized with sodium tungstate as a crosslinker was obviously enhanced. Moreover, the WPAA–TEA xerogel had absorbency values of 223.6 and 81.9 g/g for distilled water and a 0.9 wt % NaCl solution, respectively, and it showed better salt resistance and a better water‐absorbing rate than the WPAA–sodium xerogel because of the modification with triethanolamine. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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 poly(acrylic acid‐co‐acrylamide)/kaolin and release kinetics of urea from it

A series of poly(acrylic acid‐co‐acrylamide)/kaolin [poly(AA‐co‐Am)/kaolin] composites were prepared by aqueous solution copolymerization of partially neutralized acrylic acid and acrylamide in the presence of kaolin nanopowder, which was synthesized to act as a release carrier of urea fertilizer. The superabsorbent composite was swollen in aqueous solution of urea to load urea, and the effect of urea concentration on the swelling was investigated. Furthermore, the effects of the contents of crosslinker, kaolin, and acrylamide, the neutralization degree of acrylic acid, and temperature, pH, and ionic strength of release medium on water absorbency and diffusion coefficient of urea release from poly(AA‐co‐Am)/kaolin were studied systematically. It was found that urea loading percentage could be adjusted by urea concentration of swelling medium, and urea diffusion coefficient could be regulated through the contents of crosslinker, kaolin, and acrylamide, and the neutralization degree of acrylic acid. Additionally, temperature and ionic strength of release medium may also affect the urea release process. The conclusions obtained could provide theoretical basis for urea diffusion behavior in superabsorbent used in agriculture. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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