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     

Ethanol‐assisted dispersion of attapulgite and its effect on improving properties of alginate‐based superabsorbent nanocomposite

The dispersion of attapulgite (APT) as nanorod‐like single crystals is crucial to fully develop its functionality of one‐dimensional nanometer material as a filler of composite materials. In this study, APT was dispersed by the assistance of ethanol during the high‐pressure homogenization process to form individual nanorod‐like crystals. The dispersed APT was used to prepare new sodium alginate‐g‐poly(sodium acrylate‐co‐styrene)/attapulgite (NaAlg‐g‐P(NaA‐co‐St)/APT) superabsorbent nanocomposites. The effect of ethanol/water ratio on the dispersion of crystal bundles of APT was investigated by field emission scanning electron microscopy, and the results indicate that APT crystal bundles were effectively disaggregated in ν(CH₃CH₂OH) : ν(H₂O) ? 5 : 5 solution after homogenized at 50 MPa. The better dispersion of APT in NaAlg‐g‐P(NaA‐co‐St) matrix has clearly improved the gel strength (from 1300 Pa to 1410 Pa, ω = 100 rad/s), swelling capacity (442–521 g/g), swelling rate (3.3303–4.5736 g/g/s), and reswelling ability of the superabsorbent nanocomposite. Moreover, the nanocomposites showed fast swelling–deswelling responsive behavior in different saline solutions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and enhanced swelling properties of a guar gum-based superabsorbent composite by the simultaneous introduction of styrene and attapulgite

In current study, a series of novel guar gum-graft-poly(sodium acrylate-co-styrene)/attapulgite (GG-g-P(NaA-co-St)/APT) superabsorbent nanocomposites were prepared by the simultaneous graft copolymerization of partially neutralized acrylic acid (NaA), styrene (St) and attapulgite (APT) onto natural guar gum (GG), using ammonium persulfate (APS) as the initiator and N,N'-methylene-bis-acrylamide (MBA) as the crosslinking agent. Fourier Transform Infrared (FTIR) and ultravoilet (UV) spectra confirmed that NaA and St had been grafted onto GG backbones and APT participated in the polymerization reaction. The incorporation of St and APT clearly improved the surface porous morphology of the composites as exhibited by Filed Emission Scanning Electron Microscopy (FESEM). The effect of St and APT on the swelling properties and the swelling kinetics of the developed nanocomposite was investigated. Results showed that the simultaneous incorporation of proper amount of hydrophobic co-monomer St and inorganic nano-scale APT not only obviously enhanced the swelling capacity but highly improved the swelling rate, and the nanocomposite showed better salt-resistant capability and excellent pH-stability in various pH solutions.     

Preparation, Characterization and Swelling Behaviors Sodium Alginate-Graft-Acrylic Acid/Na+Rectorite Superabsorbent Composites

Novel superabsorbent composites based on sodium alginate-graft-acrylic acid (SA-g-AA) and Na⁺rectorite (Na⁺REC), i.e., SA-g-AA/Na⁺REC, were developed. The effect of the preparative conditions on the absorption of water was investigated. The structure and morphology were analyzed by infrared spectroscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results revealed that the optimal condition was 10, 0.8, and 0.03 wt% of SA/Na⁺REC, potassium persulphate and MBA, respectively. The absorbency of SA-g-AA/Na⁺REC was 641 g/g for water, or 115 g/g for 0.9 % NaCl solution. Compared to SA-g-PAA, the absorption of SA-g-AA/Na⁺REC composites in water and many water/inorganic salt solutions increased greatly. In addition, the thermal stability of the SA-g-AA/Na⁺REC composites improved, which indicated that the participation of Na⁺REC improved not only the equilibrium water absorbency, swelling rate and salt-resistant properties, but also the thermal stability of SA-g-AA.     

Enhanced swelling and responsive properties of an alginate-based superabsorbent hydrogel by sodium p-styrenesulfonate and attapulgite nanorods

In this work, a series of sodium alginate-g-poly(sodium acrylate-co-sodium p-styrenesulfonate)/attapulgite (NaAlg-g-poly(NaA-co-NaSS)/APT) superabsorbent composites were prepared by graft copolymerization using N,N’-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate as an initiator. Fourier transform infrared spectroscopy revealed that NaA and NaSS had been grafted onto NaAlg, and APT participated in polymerization reaction through reactive –OH groups. The introduction of proper amount of NaSS and APT induced the improved surface morphology, swelling capacity, and swelling rate. Moreover, the swelling behaviors of the superabsorbent composites were remarkably influenced by various salt medium, pH buffer solutions and organic solvents, and especially an intriguing swelling–deswelling behavior was observed with altering water/organic solvent ratio.     

Synthesis and swelling behaviour of poly (sodium acrylate)/sepiolite superabsorbent composites and nanocomposites

A series of novel composites and nanocomposites xerogels based on acrylic acid, sepiolite and N,N′‐methylenebisacrylamide were prepared using a solution polymerization technique at 70 °C. The quality of dispersion of the micronized sepiolite in the monomer is the crucial point for obtaining nanocomposites. A good dispersion explains the improvement of the absorbent properties of the nanocomposites with respect to the composites. This work investigates not only the influence of the mixing procedure on the swelling behaviour, but also the effect of the amount of clay on the absorbency of these hydrogels in deionized water and saline solution (0.2 wt% NaCl_(aq)). A crosslinker concentration of 5 wt% sepiolite nanocomposite superabsorbent was shown to give the best results (1419 g g^?1). Moreover, experimental results indicate that the absorbency in saline solution is smaller than that in deionized water. Rates of swelling for these absorbents were found to fit the Voigt expression. Finally, the model approximates Case II sorption in the early stages of the swelling process and Case I in the later stages. Copyright © 2006 Society of Chemical Industry     

Effect of attapulgite contents on release behaviors of a pH sensitive carboxymethyl cellulose‐g‐poly(acrylic acid)/attapulgite/sodium alginate composite hydrogel bead containing diclofenac

A series of pH‐sensitive composite hydrogel beads, carboxymethyl cellulose‐g‐poly(acrylic acid)/attapulgite/sodium alginate (CMC‐g‐PAA/APT/SA), were prepared by combining CMC‐g‐PAA/APT composite and SA, using Ca²⁺ as the ionic crosslinking agent and diclofenac sodium (DS) as the model drug. The effects of APT content and external pH on the swelling properties and release behaviors of DS from the composite hydrogel beads were investigated. The results showed that the composite hydrogel beads exhibited good pH‐sensitivity. Introducing 20% APT into CMC‐g‐PAA hydrogel could change the surface structure of the composite hydrogel beads, decrease the swelling ability, and relieve the burst release effect of DS. The drug cumulative release ratio of DS from the hydrogel beads in simulated gastric fluid was only 3.71% within 3 hour, but in simulated intestinal fluid about 50% for 3 hour, 85% for 12 hour, up to 90% after 24 hour. The obtained results indicated that the CMC‐g‐PAA/APT/SA hydrogel beads could be applied to the drug delivery system as drug carriers in the intestinal tract. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reinforcement effect of poly (methyl methacrylate)-<Emphasis Type="Italic">g</Emphasis>-cellulose nanofibers on LDPE/thermoplastic starch composites: preparation and characterization

The effect of cellulose nanofibers (CNFs) and poly [methyl methacrylate (MMA)]-grafted cellulose nanofibers (CNF-g-PMMA) on mechanical properties and degradability of a 75/25 low density polyethylene/thermoplastic starch (LDPE/TPS) blend was investigated. Graft copolymerization on CNFs was performed in an aqueous suspension by free radical polymerization using MMA as an acrylic monomer. In addition, a LDPE/TPS blend was reinforced by different amounts of CNFs (1–5 wt%) and CNF-g-PMMA (1–7 wt%) using a twin-screw extruder. A 61% grafting of PMMA on the surface of CNFs was demonstrated by gravimetric analysis. Moreover, after modification the X-ray photoelectron spectroscopy analysis showed a 20% increase of carbon atoms on the surface of CNFs and a 22.6% decrease in the oxygen content of its surface. The mechanical properties of the CNFs-modified composites were significantly improved compared to the unmodified nanocomposites. The highest tensile strength and Young’s modulus were obtained for the composites reinforced by 3 and 7 wt% CNF-g-PMMA, respectively. The degradability of cellulose nanocomposites was studied by water absorption and soil burial tests. Surface modification of CNFs lowered water absorption, and soil burial test of the LDPE/TPS blend showed improvement in biodegradability by addition of CNF-g-PMMA.     

Superabsorbent composite. X. Effects of saponification on properties of polyacrylamide/attapulgite

A novel superabsorbent composite from acrylamide (AM) and attapulgite (APT), polyacrylamide/attapulgite (PAM/APT), was prepared by polymerizing AM with the existence of APT in aqueous solution, and then saponified with NaOH solution. Considering the impacts of hydrophilic groups (? COONa, ? COOH, and ? CONH₂) on properties of the PAM/APT composite, the effects of saponification mode, molar ratio of NaOH to AM and saponification time on water absorbency, hydrophilic group content, and surface morphology were investigated systematically. The results indicate that the two‐step adding NaOH mode is superior to that of the one‐step mode. Among the superabsorbent composite incorporated with 30 wt% APT, the composite saponified at 95°C for 2 h with the molar ratio of 0.6 for NaOH to AM acquired the highest water absorbencies of 1715g g^?1 and 87.8g g^?1 in distilled water and in 0.9 wt% NaCl solution, respectively. The molar ratio of various hydrophilic groups at this time was 10:3:11 for ? COONa, ? COOH, and ? CONH₂ determined using linear potentiometric titration method. POLYM. ENG. SCI. 46:1762–1767, 2006. © 2006 Society of Plastics Engineers.     

Preparation of polyacrylamide/graphite oxide superabsorbent nanocomposites with salt tolerance and slow release properties

Novel polyacrylamide/graphite oxide (PAM/GO) superabsorbent nanocomposites were synthesized by a simple solution polymerization of acrylamide using N,N ′‐methylenebisacrylamide as crosslinker and ammonium persulfate as initiator. The well dispersion of GO nanoplatelets in the polymeric network results in a remarkable improvement on the comprehensive swelling performance of the resulting superabsorbent nanocomposites. The water absorption experimental results show that the superabsorbent nanocomposites could absorb water as twice as that of crosslinked polyacrylamide (PAM) superabsorbent with a weight gain of 400 g g^?1 with a low loading of GO. The salt tolerance and water‐retention ability of the resulting PAM/GO superabsorbent nanocomposites are also enhanced compared with PAM. Moreover, by embedding of ammonium salt into PAM/GO network, the PAM/GO superabsorbent nanocomposites also exhibit a slow release behavior of ammonium salt from network when swelling in water, which makes the PAM/GO superabsorbent nanocomposites multifunctional absorbent materials with great potential for agricultural and horticultural applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Study on Superabsorbent Composite, 14

Summary: Organo‐attapulgite (organo‐APT) was prepared by modifying APT using four quaternary ammonium salts with various lengths of the alkyl group, including (octyl)trimethylammonium bromide (OTMABr) and (stearyl)trimethylammonium chloride (STMACl), etc. A series of composite hydrogels, poly(acrylic acid)/organo‐APT, from acrylic acid (AA), and organo‐APT was prepared by aqueous polymerization, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The organification and organification degree of APT as well as the corresponding composites were characterized by FTIR, TGA, and XRD. The effects of the length of the alkyl group for different quaternary ammonium salts, organification degree of APT, and organo‐APT content on water absorbency and swelling behaviors in various electrolyte solutions were investigated in this study. Equilibrium water absorbency strongly depends on chain length of the alkyl group of quaternary ammonium salts, organification degree of APT as well as organo‐APT content. Longer alkyl group, higher organification degree, and proper organo‐APT content are of benefit for the improvement of equilibrium water absorbency. Equilibrium water absorbency in distilled water for PAA/APT was enhanced from 350.1 to 562.1 g · g^?1 after 10 wt.‐% organo‐APT, modified with STMACl for the highest degree, was introduced. The kind of cation is the key factor influencing equilibrium water absorbency of these composite hydrogels in electrolyte solutions. Organification of APT could enhance responsiveness of the corresponding composite hydrogel to electrolyte solutions.

Schematic structure of PAA/organo‐APT composite in a dry state (left) and in a swollen state (right).     

New aramid‐based nanocomposites: Synthesis and characterization

New type of nanocomposites containing various proportions of montmorillonite in aromatic polyamide was prepared via solution intercalation method. Aramid chains were synthesized by reacting 4,4′‐oxydianiline with isophthaloyl chloride in N,N′‐dimethyl acetamide. Dodecylamine was used as swelling agent to change the hydrophilic nature of montmorillonite into organophilic. Appropriate amounts of organoclay were mixed in the polymer solution using high‐speed mixer for complete dispersion of the clay. Thin films cast from these materials after evaporating the solvent were characterized by XRD, TEM, mechanical, thermal, and water absorption measurements. The structure and morphology of the nanocomposites determined by XRD and TEM revealed the formation of exfoliated and intercalated clay platelets in the aramid matrix. Mechanical data indicated improvement in the tensile strength and modulus of the nanocomposites with clay loading up to 6 wt%. The glass transition temperature increased up to 12 wt% clay content and thermal stability amplified with increasing clay loading. The water absorption reduced gradually as a function of organoclay and approached to zero with 20 wt% organoclay in the aramid. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Synergetic association of grafted PLA and functionalized graphene on the properties of the designed nanocomposites

The synergetic association of poly(lactic acid) grafted with maleic anhydride (MA-g-PLA) containing 0.44 wt% of maleic anhydride and epoxy-functionalized graphene (GFe) on the properties of the designed nanocomposites was studied. Rheological, mechanical and barrier properties of PLA nanocomposites were studied using different content of epoxy-functionalized graphene and MA-g-PLA compatibilizer. The PLA/MA-g-PLA/GFe nanocomposites prepared by melt blending, containing 5 wt% of MA-g-PLA, yield a maximum in storage modulus G′ and a rheological plateau at low frequencies, with a content of epoxy-functionalized graphene comprised between 4 and 7 wt%. This phenomenon was ascribed to a pseudo-solid behavior resulting from the high degree of epoxy-functionalized graphene exfoliation due to strong interfacial interactions with PLA and epoxy-functionalized graphene. The better mechanical and barrier performances were obtained with PLA/GFe containing 10 wt% of epoxy-functionalized graphene and 5 wt% of MA-g-PLA compatibilizer. The variation of the percentage of compatibilizer showed that 5 wt% of maleated PLA was sufficient to improve the thermal, rheological, mechanical and barrier properties of the PLA nanocomposite containing 7 wt% of epoxy-functionalized graphene.     

Grafted CMC/silica gel superabsorbent composite: Synthesis and investigation of swelling behavior in various media

In the present study, we attempt to synthesize and characterize novel CMC-g-poly (acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid)/silica gel composite. Infrared spectroscopy and TGA thermal analysis were carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was examined by scanning electron microscopy. The effect of reaction variables affecting on water absorbency of the composite and swelling behavior in various solvents, salt, and pH solutions was investigated. Maximum water absorbency of the optimized final product was found to be 4000 g/g in distilled water. The absorbency under load (AUL) of the hydrogel was also determined by using an AUL tester at various applied pressures. Finally, dynamic swelling kinetics of the hydrogel was studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

Preparation,Characterization, and Drug-Release Behaviors of a pH-Sensitive Composite Hydrogel Bead Based on Guar Gum,Attapulgite, and Sodium Alginate

A novel guar gum-g-poly (acrylic acid)/attapulgite/sodium alginate (GG-g-PAA/APT/SA) composite hydrogel bead with excellent pH sensitivity was prepared via a facile ionic gelation approach and characterized by FTIR and SEM techniques. The effect of APT content on the encapsulation efficiency (EE), swelling ratio, and drug release behaviors of the beads was investigated and the in-vitro release kinetics were also evaluated using diclofenac sodium (DS) as the model drug. The results indicate that the burst release effect of DS drug was eliminated due to the incorporation of APT, and the DS cumulative release was clearly decreased with increasing the APT content.     

Removal of methylene blue from aqueous solution by sorption on lignocellulose-g-poly(acrylic acid)/montmorillonite three-dimensional cross-linked polymeric network hydrogels

Batch lignocellulose-g-poly(acrylic acid)/montmorillonite (LNC-g-PAA/MMT) hydrogel nanocomposites were applied as adsorbents. The nanocomposites were characterized by FTIR, XRD, SEM, and TEM. The results showed that montmorillonite (MMT) could react with the monomers and change the structure of polymeric network of the traditional superabsorbent materials, an exfoliated structure was formed in the nanocomposites. The effect of process parameters such as MMT content (wt%), contact time (t), initial concentration of dye solution (C ₀), adsorption temperature (T), and pH value (pH) of the dye solution for the removal of methylene blue (MB) from aqueous solution were also studied. The results showed that the adsorption capacity for MB increased with increasing contact time, initial dye concentration, and pH value, but decreased with increasing MMT content and temperature. The adsorption kinetics were better described by the pseudo-second-order equation, and their adsorption isotherms were better fitted for the langmuir equation. By introducing 20 wt% MMT into LNC-g-PAA polymeric network, the obtaining hydrogel composite showed the high adsorption capacity 1994.38 mg/g and economic advantage for MB. The desorption studies revealed that the composite provided the potential for regeneration and reuse after MB dye adsorption, which implied that the composite could be regarded as a potential adsorbent for cationic dye MB removal in a wastewater treatment process.     

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     

Water absorption behavior of different types of organophilic montmorillonite‐filled polyamide 6/polypropylene nanocomposites

The water absorption behavior of different types of organophilic montmorillonite (OMMT)‐filled polyamide 6/polypropylene nanocomposites with and without compatibilizers (maleated PP or PP‐g‐MA and maleated styrene‐ethylene/butylene‐styrene or SEBS‐g‐MA) was evaluated. Four different types of OMMT, i.e., dodecylamine‐modified MMT (D‐MMT), 12 aminolauric acid‐modified MMT (A‐MMT), stearylamine‐modified MMT (S‐MMT), and commercial organo‐MMT (C‐MMT) were used as reinforcement. The water absorption response of the nanocomposites was studied and analyzed by tensile test and morphology assessment by scanning electron microscopy (SEM). The kinetics of water absorption of the nanocomposites conforms to Fick's law. The M_m and D are dependent on the types of OMMT and compatibilizers. The equilibrium water content and diffusivity of PA6/PP blend were increased by the addition of OMMT but decreased in the presence of compatibilizers. On water absorption, both strength and stiffness of the nanocomposites were drastically decreased, but the ductility was remarkably increased. Both PP‐g‐MA and SEBS‐g‐MA played an effective role as compatibilizers for the nanocomposites. This was manifested by their higher retention ability in strength and stiffness (in the wet and re‐dried states), reduced the equilibrium water content, and diffusivity of the nanocomposites. POLYM. COMPOS., 2010. © 2009 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