Effects of modified vermiculite on the synthesis and swelling behaviors of hydroxyethyl cellulose-<Emphasis Type="Italic">g</Emphasis>-poly(acrylic acid)/vermiculite superabsorbent nanocomposites

A series of hydroxyethyl cellulose-g-poly(acrylic acid)/vermiculite (HEC-g-PAA/VMT) superabsorbent nanocomposites were prepared by radical solution polymerization among hydroxyethyl cellulose (HEC), partially neutralized acrylic acid (AA), raw vermiculite (RVMT), acidified vermiculite (AVMT) and organo-vermiculite (OVMT) in the presence of initiator ammonium persulfate (APS) and crosslinker N,N’-methylenebisacrylamide (MBA). FTIR results revealed that AA was grafted onto HEC backbone and VMT participated in polymerization. VMT was exfoliated during polymerization reaction and a nanocomposite structure was formed as shown by XRD and TEM analysis. Effects of VMT content, concentration of HCl solution and organification degree of OVMT on water absorbency were investigated and the swelling kinetics of the developed nanocomposites was also evaluated. Results showed that incorporation of VMT greatly enhanced the water absorbency, and the modified VMT by acidification and organification can improve the water absorbency more remarkably than raw one. OVMT can improve the swelling capabilities and swelling rate to the highest degree in contrast to RVMT and AVMT.     

Superabsorbent composite XXII: Effects of modified sepiolite on water absorbency and swelling behavior of chitosan‐g‐poly(acrylic acid)/sepiolite superabsorbent composite

In this work, a series of chitosan‐g‐poly(acrylic acid)/sepiolite (CTS‐g‐PAA/ST) superabsorbent composites containing raw sepiolite, acid‐activated sepiolite, and cation‐exchanged sepiolite were synthesized by free‐radical graft polymerization in aqueous solution, using N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The effects of raw sepiolite, acid‐activated sepiolite, and cation‐exchanged sepoilite on equilibrium water absorbency, swelling rate, and swelling behavior in different pH value solution of superabsorbent composites were systematically investigated. The results from FTIR spectra showed that chitosan and sepiolite participated in graft polymerization reaction with acrylic acid. The introduction of acid‐activated and cation‐exchanged sepiolite into chitosan‐g‐poly(acrylic acid) polymeric network could improve water absorbency and swelling rate compared with that of the raw sepiolite. All prepared samples have similar swelling behavior in different pH solutions and the equilibrium water absorbencies of samples keep roughly constant in the pH range from 4 to 12. POLYM. COMPOS., 2010. © 2009 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     

Study on superabsorbent composites. XXI. Synthesis,characterization and swelling behaviors of chitosan‐g‐poly(acrylic acid)/organo‐rectorite nanocomposite superabsorbents

A novel chitosan‐g‐poly(acrylic acid)/organo‐rectorite (CTS‐g‐PAA/OREC) nanocomposite superabsorbent was synthesized by aqueous polymerization using N, N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. Rectorite was organified with four different degree of hexadecyltrimethyl ammonium bromide, and the organification of rectorite was proved by FTIR and XRD. The effect of organification degree of rectorite on water absorbency of CTS‐g‐PAA/OREC with different organo‐rectorite content was investigated. The swelling behaviors in distilled water and various pH solutions were also studied. The results from IR spectroscopy and XRD data show that acrylic acid had been grafted polymerization with chitosan and organo‐rectorite and formed nanocomposite. Introducing organo‐rectorite into the CTS‐g‐PAA polymeric network can improved water absorbency and swelling rate of CTS‐g‐PAA/OREC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Utilization of waste polystyrene and starch for superabsorbent composite preparation

A superabsorbent composed of waste polystyrene, starch, and acrylic acid was prepared through emulsion polymerization. The effects of major factors such as starch, acrylic acid, initiator, crosslinker, and bentonite contents and the neutralization degree of acrylic acid on water absorbency were investigated to obtain optimum conditions with high swelling capacity. The superabsorbent hydrogel was characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The FTIR results confirmed that the grafting polymerization took place among the polystyrene, acrylic acid, starch, and bentonite. The introduction of bentonite particles into the polystyrene‐g‐poly (acrylic acid)‐co‐starch system could increase the water absorbency. The superabsorbent composite containing 3 wt % bentonite had the highest water absorbency (500 g/g in distilled water and 49 g/g in 0.9 wt % NaCl solution). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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     

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 characterization of superabsorbent composite by using glow discharge electrolysis plasma

A convenient and effective technique for polymerization to produce the poly(acrylic acid-co-acrylamide)/montmorillonite superabsorbent composite in aqueous solution was developed, in which the reaction was initiated by the glow discharge electrolysis (GDE) plasma rather than chemical initiators. The resulted superabsorbent has higher water absorbency, for example, 1024 g g⁻¹ for distilled water and 56 g g⁻¹ for 0.9% NaCl solution. To optimize the synthesis conditions, the following parameters were examined in detail: the discharge voltage, discharge time, ratio of acrylic acid to acrylamide, neutralization of acrylic acid, amount of crosslinking agent and montmorillonite added. The superabsorbent composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Results indicated that montmorillonite was effectively bonded with polymer. Moreover, the water absorbency, water retention and thermal stability of the superabsorbent composite prepared by GDE were higher than those of the superabsorbent composite by conventional chemical method under the same polymerization conditions.     

Synthesis and swelling behaviors of semi‐IPNs superabsorbent resin based on chicken feather protein

A novel chicken feather protein‐g‐poly (potassium acrylate)/polyvinyl alcohol (CFP‐g‐PKA/PVA) semi‐IPNs superabsorbent resin (SAR) based on feather protein, acrylic acid (AA), and polyvinyl alcohol (PVA) was synthesized by graft copolymerization and semi‐interpenetrating technology. The results from FTIR, SEM, and TGA analysis showed that both CFP and PVA reacted with PKA during the polymerization process. The effects of AA, PVA, initiator and crosslinker content on water absorbency of semi‐IPNs SAR were studied. The swelling behavior in various pHs and saline solutions were also investigated. The water absorbency of SAR reached the maximum at pH = 6. The effect of the five cations on swelling had the following order: Al³⁺ > Ca²⁺ > Mg²⁺ > K⁺ > Na⁺. The highest water absorbency in distilled water and 0.9 wt % NaCl solutions were 714.22 and 70.08 g g^?1, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39748.     

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     

GG-g-PAA/LOESS复合高吸水性树脂的制备与性能

以瓜尔胶(GG)、丙烯酸(AA)和黄土(LOESS)为原料,过硫酸铵(APS)为引发剂,N,N'-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了瓜尔胶接枝聚丙烯酸/黄土(GG-g-PAA/LOESS)复合高吸水性树脂。采用FTIR和SEM对其结构进行了表征,研究了LOESS的添加量对复合高吸水性树脂的溶胀能力和溶胀动力学的影响,考察了复合高吸水性树脂的保水性能、反复溶胀性以及在不同pH溶液中的吸水性能。结果表明,瓜尔胶、丙烯酸和LOESS发生了接枝共聚,体系中引入LOESS能够显著提高复合高吸水性树脂的吸水性能。当LOESS的质量分数为2%时,该树脂最高吸水倍率可达602 g/g,室温下6 d后,其保水率仍达28%,5次反复溶胀,吸水倍率仍能保持初始时的49%。此外,该复合高吸水性树脂还表现出优异的pH稳定性。     

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     

Study on superabsorbent composite XXV. Synthesis,characterization, and swelling behaviors of poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composites

In this work, a novel poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composite was prepared by graft copolymerization among acrylic acid, N‐acryloylmorpholine and attapulgite in aqueous solution, using N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The result from FTIR spectra showed that  OH of attapulgite participated in graft copolymerization with acrylic acid and N‐acryloylmorpholine. Proper monomer ratio and atapulgite content could form a loose surface, and improve reswelling ability and initial swelling rate. The buffer action of the  COOH and  COO⁻ groups in the superabsorbent composite keeps the water absorbency a rough constant in the pH range of 4.4–9.6. Both polarity and structure of an organic solvent are responsible for the phase transition point of the superabsorbent composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

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     

Study on superabsorbent composites. IX: Synthesis,characterization and swelling behaviors of polyacrylamide/clay composites based on various clays

A series of clay-based superabsorbent composite from acrylamide (AM) and various clays, such as attapulgite, kaolinite, mica, vermiculate and Na⁺-montmorillonite, was prepared by free-radical aqueous polymerization, using N,N′-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator, and then saponified with sodium hydroxide solution. In this paper, the reaction mechanism and thermal stability of the superabsorbent composites incorporated with various clays were characterized by FTIR, XRD and TGA, respectively. The effects of clay kind and clay content on equilibrium water absorbency of these composites were also investigated and compared. In addition, the influences of clay kind on comprehensive swelling behaviors of the PAM/clay superabsorbent composites were studied. The results indicated that the introduced clays could influence physicochemical properties of obtained superabsorbent composites. Mica could improve thermal stability of corresponding superabsorbent composites to the highest degree comparing with the other clays. The PAM/clay superabsorbent composites incorporated with 10 wt% clay of various kinds were all endowed with equilibrium water absorbency of more than 1300 g g⁻¹. The equilibrium water absorbency decreases with increasing clay content and correlates with the kind of clay. Attapulgite-based superabsorbent composite was endowed with higher water absorbency in univalent cationic saline solution, however, the vermiculite- and the kaolinite-based ones acquired the highest water absorbency in CaCl₂ and FeCl₃ aqueous solution, respectively. Moreover, the superabsorbent composites incorporated with Na⁺-montmorillonite have higher swelling rate and that of doped with mica was endowed with higher reswelling capability.     

Synthesis,characterization, and swelling behavior of alginate‐g‐poly(sodium acrylate)/kaolin superabsorbent hydrogel composites

A novel superabsorbent composite based on sodium alginate and the inorganic clay kaolin was synthesized via the graft copolymerization of acrylic acid (AA) in an aqueous medium with methylene bisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. The effects of reaction variables, such as the MBA, AA, and APS concentrations and the alginate/kaolin weight ratio, on the water absorbency of the composite were systematically optimized. Evidence of grafting and kaolin interactions was obtained by a comparison of the Fourier transform infrared spectra of the initial substrates with that of the superabsorbent composite, and the hydrogel structure was confirmed with scanning electron microscopy. The results indicated that with an increasing alginate/kaolin weight ratio, the swelling capacity and gel content increased. The effects of various salt media were also studied, along with the swelling kinetics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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 of wheat straw composite superabsorbent

A novel wheat straw composite superabsorbent was prepared by graft polymerization with acrylic acid (AA), acrylamide (AM), and maleic anhydride‐modified wheat straw in aqueous solution, using N,N‐methylene‐bis‐acrylamide (MBA) as a cross‐linker and ammonium persulfate (APS) and sodium bisulfite (SBS) as redox initiators. Factors influencing the degree of carboxylation, such as reaction time, reaction temperature, and the amount of maleic anhydride, were investigated. Morphologies and structure of the wheat straw composite superabsorbent were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X‐ray diffraction (XRD). Water absorption of wheat straw composite superabsorbent was rapid, requiring 13.1 min to reach 63% of equilibrium absorbency (781 g/g). FTIR spectra indicate that maleic anhydride has been reacted onto the wheat straw backbone and the structure of wheat straw graft copolymer is formed. SEM data show that the fibrous morphology of wheat straw disappears and gel aggregates with many large microporous holes are formed after wheat straw graft modification. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3404–3410, 2013     

Preparation of superabsorbent based on the graft copolymerization of acrylic acid and acrylamide onto konjac glucomannan and its application in the water retention in soils

A new konjac glucomannan (KGM)-based superabsorbent polymer, KGM-g-poly(acrylic acid-co-acrylamide), was prepared by the free radical grafting solution polymerization of acrylic acid (AA) and acrylamide (AM) monomers onto KGM in the presence of N,N′-methylenebisacrylamide as a crosslinker with potassium persulfate as an initiator. The effects of reaction parameters, including the amount of crosslinking agent and initiator, the weight ratio of both (AA + AM) to KGM and AM to (AA + AM), neutralization degree of AA, bath temperature, and reaction time, on the water absorbency of the superabsorbent were investigated. The Fourier transform infrared spectroscopy was used to characterize the structures of the copolymer. The maximum water absorbency of the optimized product was 650 g/g for distilled water and 70 g/g for a 0.9 wt % aqueous NaCl solution. Furthermore, the water retention of the copolymer in soils was studied. The effect of the copolymers on the aggregate distribution of soils was also evaluated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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