Equilibrium Swelling Capacity Research Articles

Hybrid super absorbent resin based on waste slag modified zeolite: A potential component adopted to agricultural water retention

The hybrid super absorbent resin (SAR), Poly(acrylicacid-co-acrylamide-co-2-acrylamido-2-methyl-1-propane sulfonic acid) based on zeolite synthesized from solid waste slag (P(AA-co-AM-co-AMPS)/zeolite) was synthesized. The chemical and structural characteristics of the materials were examined through FTIR, XRD, and SEM studies. In the presence of zeolite, the flat surface of the composite transformed into interconnected porous structure. The deionized water equilibrium swelling capacity of the hybridized SAR (835.79 g/g) was higher than that of the pure SAR (524.53 g/g). As much as 40 % of the water was released from the fully swollen hybrid SAR when it was centrifuged. P(AA-co-AM-co-AMPS)/zeolite had a swelling loss rate just of 27.64 % after five swelling/drying cycles. In addition, it still had good absorption in ionic salt solutions of different concentrations and good water retention at different temperatures. This confirmed that the hybridized SAR had excellent water holding capacity and salt solution adsorption. The FTIR and XRD results showed that the excellent performance of the hybridized SAR may originate from the interconnection of the zeolite and the pure SAR. The P(AA-co-AM-co-AMPS)/zeolite may be utilized as an agricultural water retaining agent.

Impact of composition and salinity on swelling and gel strength of poly (acrylamide-co-acrylic acid) preformed particle gel

The effects of various material compositions and reservoir environments on the ultimate strength and swelling kinetics of a commercial preformed particle gel (PPG) have been investigated. This study used different ratios of acrylamide and acrylic acid copolymers with a specific crosslinker concentration. Results have indicated that increasing the acrylic acid proportion enhances the PPGs’ ability to swell but weakens their network structure. In contrast, increasing the crosslinker content decreases the swelling ratio and increases the gel strength. The highest equilibrium swelling capacity among the six preformed particle gel samples was obtained for PPG2, which has the highest acrylic acid amount and the lowest crosslinker content, with a swelling ratio of 2400 g/g in deionized water and 59.8 g/g in brine 1 (67535.8 mg/l). On the contrary, PPG5, with the lowest acrylic acid and highest crosslinker content, has a swelling capacity of 239 g/g and more than 17 g/g in distilled and brine 1, respectively. Yet, PPG5 has the highest swollen gel strength of 615.5 Pa in deionized water and 3344 Pa in brine 1. The PPGs’ swelling ratios showed stepwise improvements along with increasing temperature, notably after 50 °C, yet, the storage modulus (G′) was negatively affected. The PPGs revealed the highest swelling behavior in pH 6–8, decreasing dramatically in more acidic and basic conditions. The swelling ratios of the PPGs in brine 1 at 50 °C were between 12 and 32 g/g, having strengths in the range of 566–5508 Pa, depending on the crosslinker ratio. The PPGs also demonstrated the ability to compete with other commercial PPGs as they have shown physical and thermal stability when aging at 50 °C, specifically those with high crosslinker content (PPG5).

An efficient pH‐responsive kappa‐carrageenan/tamarind kernel powder hydrogel for the removal of brilliant green and rose bengal from aqueous solution

AbstractThe objective of this study was to develop an eco‐friendly, cost‐effective, and efficient adsorbent using kappa‐carrageenan (KCG) and tamarind kernel powder (TKP) based cross‐linked 3‐D network hydrogel. The equilibrium swelling capacity of 1429% was achieved by optimization studies. The KCG/TKP hydrogel was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy, energy dispersive spectroscopy, and thermogravimetric analysis. This hydrogel was employed for the efficient removal of brilliant green (BG) and rose bengal (RB) dye from wastewater. BG and RB were used as a cationic and anionic model dye, respectively. The adsorption capacity of model dyes on KCG/TKP was investigated under different parameters like dye concentration, pH, temperature, and adsorbent amount. With remarkable adsorption capacity, the hydrogel demonstrated a strong dependence on the pH of the medium. The kinetics, adsorption isotherm, thermodynamic studies, and reusability were investigated. The KCG/TKP hydrogel follows pseudo‐second‐order kinetics and the Langmuir isotherm model for the adsorption of both BG and RB model dyes. Spontaneity and exothermic behavior of the adsorption process were revealed by thermodynamic findings. At pH 9, the maximum adsorption capacity of BG was 840.33 mg g−1 while the maximum adsorption capacity of RB was 168.06 mg g−1 at pH 5.

Methacrylated alkali lignin grafted P(Nipam-Co-AAc) copolymeric hydrogels: Tuning the mechanical and stimuli-responsive properties

The current study reports the preparation of lignin grafted temperature and pH responsive hydrogels through copolymerization of N-isopropylacrylamide, acrylic acid and varying amount of lignin methacrylate (LMA = 50, 100, 150 and 200 mg) as crosslinker adopting radical polymerization technique. Functional group and structural characterizations were carried out to confirm hydrogels synthesis and their network structure. The variation in pore size on addition of lignin revealed the tuning of pores as well as swelling capacity of the hydrogels by suitable amount of LMA. All LMA grafted hydrogels showed temperature responsive behavior and pH dependent sensitivity in swelling, with reduced equilibrium swelling capacity values compared to sample without lignin. In alkali medium at room temperature, the maximum swelling capacity with 48% higher retention was noticed, while a significant reduction in swelling was observed at 40 °C in all media. The addition of lignin still preserved the tensile strength up to 100 kPa and compressive load bearing ability up to 30 kPa in freeze dried state with adequate interfacial stress transfer. An increase in lignin concentration showed enhanced storage modulus (~two-fold increase), adequate loss modulus values and improved cell viability, which paves the way for possible biomedical applications.

Electro‐responsive semi‐IPN hydrogel with enhanced responsive property for forward osmosis desalination

AbstractAn electro‐responsive hydrogel with semi‐interpenetrating polymer networks (semi‐IPN) composed of crosslinked poly(2‐acrylamido‐2‐methyl‐l‐propanesulfonic acid‐co‐acrylamide) (P(AMPS‐AM)) and linear polyelectrolyte polyacrylic acid (PAA) was explored. The semi‐IPN hydrogel was characterized with different methods and then used as advanced draw agent toward high water recovery for forward osmosis (FO) desalination. The swelling kinetics of the semi‐IPN hydrogel was investigated, and the electro‐responsive nature of the hydrogel under electric stimulus (in direct contact with electrodes) was determined. Results indicated that in comparison with pure P(AMPS‐AM) hydrogel, the semi‐IPN hydrogel exhibited a loose network structure with more pores. In addition, a higher equilibrium swelling capacity and more pronounced deswelling under electric stimulus can be observed for the semi‐IPN hydrogel. Furthermore, the semi‐IPN hydrogel displayed a similar initial water flux of 2.20 L m−2 h−1 (LMH) from 2 g/L NaCl solution of a lab‐scale FO process. Importantly, the semi‐IPN hydrogel had a 25% increase in water recovery efficiency under the electric stimulus of 15 V, and showed better recyclability during three cycles of regeneration compared with pure P(AMPS‐AM). The mechanism of enhanced dewatering nature for the semi‐IPN hydrogel under electric stimulus was elucidated. These results indicate this new hydrogel's potential as a promising candidate for improving FO performance.

Effects of hydrolysis treatment on the structure and properties of semi‐interpenetrating superabsorbent polymers

AbstractA semi‐interpenetrating polymer network superabsorbent polymer based on sodium lignosulfonate‐graft‐poly(acrylic acid‐acrylamide)/potassium dihydrogen phosphate and polyvinyl alcohol (PVA/SL‐g‐P[AA‐AM]/KDP) was synthesized by using solution polymerization. The PVA/SL‐g‐P(AA‐AM)/KDP was further hydrolyzed in NaOH solution. The structure, thermal stability, and morphologies of samples were examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results of FTIR, TGA, and DSC showed that PVA interpenetration through SL‐g‐P(AA‐AM)/KDP network has occurred, and PVA/SL‐g‐P(AA‐AM)/KDP was successfully alkaline hydrolyzed. From the SEM images, the high porous and loose surface structure of polymers was formed after hydrolysis, which greatly increased the specific surface area. Samples after hydrolysis exhibited higher equilibrium swelling capacity (1963 g/g) compared to the nonhydrolyzed samples (866 g/g). The swelling kinetics of all samples well complied with the pseudo‐second order swelling kinetics model. Simple hydrolysis treatment not only improved the swelling capacity of PVA/SL‐g‐P(AA‐AM)/KDP but also induced an enhancement on its water retention performance, which made it potentially useful as a water retention agent in the revegetation of abandoned mines or slope wasteland.

Preparation of poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropan sulfonic acid)‐g‐Carboxymethyl cellulose/Titanium dioxide hydrogels and modeling of their swelling capacity and mechanic strength behaviors by response surface method technique

AbstractIt is very important that new generation, unique, high mechanical strength, and biocompatible hydrogel composites are developed due to their potential to be used as biomaterials in the biomedical field. Modeling of the swelling capacity and mechanical strength behavior of hydrogels is a domain of steadily increasing academic and industrial importance. These behaviors are difficult to model accurately due to hydrogels show very complex behavior depending on the content. In this study, a series of poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropan sulfonic acid)‐g‐carboxymethyl cellulose/TiO2 (poly(AAm‐co‐AMPS)‐g‐CMC/TiO2) superabsorbent hydrogel composites were prepared by free‐radical graft copolymerization in aqueous solution. Structural and surface morphology characterizations were conducted by using Fourier‐transform infrared spectroscopy and scanning electron microscope analysis techniques. For modeling the equilibrium swelling capacity and fracture strength behaviors of hydrogels, the composition parameters (such as mole ratio of AMPS/AAm, wt% of CMC, and wt% of TiO2) was proposed by response surface method (RSM) Design Expert‐10 software. Statistical parameters showed that the RSM model has good performance in modeling the swelling capacity and mechanic fracture strength behaviors of poly(AAm‐co‐AMPS)‐g‐CMC/TiO2 hydrogel composites. According to the RSM model results, the maximum swelling capacity and fracture strength values were calculated as 270.39 g water/g polymer and 159.23 kPa, respectively.

Pullulan/poly(N‐vinylimidazole) cryogel: An efficient adsorbent for methyl orange

AbstractPullulan/poly(N‐vinylimidazole) (PNVI) hybrid cryogels were synthesized under free radical polymerization and chemical crosslinking conditions in an alkaline, aqueous solution of pullulan (PUL), N‐vinylimidazole (NVI), ammonium persulfate and epicholorohydrin (ECH) at −18°C. PUL and PNVI cryogels alone were also synthesized under similar conditions. Optimum cryogel formation conditions were determined by considering product yields and gel fractions of the samples. The products were characterized by elemental analysis, FTIR‐ATR spectrometry, Thermal gravimetric analysis, and scanning electron microscopy (SEM) analyses. It has been found that PUL/PNVI hybrid samples bear improved physicochemical properties compared to ECH crosslinked PUL and PNVI samples alone. They act as hydrogels in aqueous medium reaching equilibrium swelling capacity values of the order of 600%. Dried PUL/PNVI cryogels show higher thermal stability than the dried cryogels of the parent polymers and maintain their physical integrity over a prolonged time period. Macroporous morphology was revealed by SEM analysis. Having 54.2 mg/g maximum equilibrium adsorption capacity in 200 ppm methyl orange solution and maintaining 95% of its adsorption capacity at the end of seven consecutive adsorption/desorption cycles, PUL/PNVI cryogel proved to be an efficient and durable dye adsorbent using methyl orange as the model compound in aqueous solution.

Swelling behavior and mechanical properties of Chitosan-Poly(N-vinyl-pyrrolidone) hydrogels

Abstract In this research, three modified chitosan-based hydrogels are synthesized, i.e., a crosslinked chitosan hydrogel and semi- and fully-interpenetrating polymer network (IPN) chitosan hydrogels fabricated using poly(N-vinyl-pyrrolidone). A non-modified chitosan hydrogel was also synthesized as a control. These samples were compared regarding their swelling behavior and mechanical properties. The hydrogels were characterized by Fourier Transform Infrared (FTIR) analysis and microscopy observations. The effect of crosslinking on the swelling capacity and on the swelling kinetics were evaluated in distilled water, simulated gastric fluid (SGF), and simulated intestinal fluid (SIF) at 37 °C, and the data were interpreted using various kinetic models. Finally, the mechanical properties were evaluated based on the tensile strength using a universal tensile testing machine. The results revealed that the swelling process conformed to the Schott model (pseudo-second-order kinetics), with Fickian diffusion as the diffusion mechanism type. The hydrogels all showed similar trends in their swelling kinetics. However, the full-IPN hydrogel exhibited the lowest equilibrium swelling capacity and the highest swelling rate. The mechanical test results indicate that the crosslinking model affects the resulting tensile strength.

Preparation and characterization of environmentally friendly agar/κ-carrageenan/montmorillonite nanocomposite hydrogels

In the present study, for the first time, agar/κ-carrageenan and agar/κ-carrageenan/montmorillonite hydrogel materials were prepared by the free-radical crosslinking reaction of agar and κ-carrageenan in the presence of triethylene glycol divinyl ether (TEGDE) as the crosslinker agent. Here, montmorillonite (MMT) modified with phenylalanine was used as additive agent. Agar/κ-carrageenan hydrogel materials with and without MMT were characterized by FTIR, SEM and XRD analyses. The effect of free radical initiator (ammonium persulfate, APS) concentration, crosslinking agent (TEGDE) concentration, reaction temperature, polysaccharide ratio and MMT concentration on the swelling performance and surface property of hydrogel material was investigated and optimum reaction conditions were determined. Maximum equilibrium swelling capacity of the agar/κ-carrageenan hydrogel was found to be 2523 % under the optimum conditions ([APS] = 5 × 10−4 M, [TEGDE] = 5 × 10−4 M, T = 70 °C and magar:mκ-carrageenan = 1:4). An increase of the MMT content within hyrogel matrix led to a decrease in the swelling values of hydrogels. All of the hydrogels prepared in various formulations exhibited non-Fickian swelling behavior. New hydrogel materials obtained from this study could be potential candidates for biomedical applications.

Eco-friendly polymer nanocomposite hydrogel enhanced by cellulose nanocrystal and graphitic-like carbon nitride nanosheet

The eco-friendly sodium carboxymethylcellulose (CMC-Na)/polyvinyl alcohol (PVA) hydrogel reinforced with cellulose nanocrystal (CNC) and graphitic-like carbon nitride (g-C3N4) was firstly prepared as smart adsorption hydrogel with mechanical, thermal and swelling response. Encouragingly, the mechanical properties of the g-C3N4/CNCs-H hydrogel were enhanced with simply changing the content of g-C3N4. The 1.0% g-C3N4/CNCs-H hydrogel had outstanding tensile strength (up to 648 KPa), excellent elongation (1169%) and satisfactory toughness (340 KJ/m3). These enhancements were due to the inherently superior properties of the prepared CMC-Na/PVA and the synergistic effect of strong hydrogen bonding interactions between g-C3N4, CNCs and CMC-Na/PVA chains. The as-prepared g-C3N4/CNCs-H hydrogel has high equilibrium swelling capacity (90.47–117.3 g/g), which greatly improved the adsorption capacity of methylene blue (MB, qe > 198.6 mg/g). The adsorption properties of MB on the as-prepared hydrogel fitted well with the pseudo-second-order kinetic model and the Langmuir isotherm model. It was showed that the interaction of π-π stacking and hydrogen bonds resulted in the high adsorption capacity of the hydrogels. This study presented a basis and demonstration for the application of hydrogels in contaminants removal in poisonous waterbodies.

Sodium alginate/poly(4-vinylpyridine) polyelectrolyte multilayer films: Preparation, characterization and ciprofloxacin HCl release

Polyelectrolyte multilayer (PEC) films of sodium alginate (Na-Alg) and poly(4-vinylpyridine) (P4VP) were prepared and were loaded with an antibacterial agent, ciprofloxacin HCl (CIP.HCl) aiming to design new hydrophilic films with controlled physicochemical properties and drug release behaviour that may find application as components of transdermal drug delivery systems. The PEC films were characterized by SEM, XRD, TGA, AFM and FTIR spectroscopy. The hydrophilicity of the PEC films was examined by using contact angle measurement. The number of layers and the nature of the outer layer affect the physicochemical characteristics, CIP.HCl loading and release behaviour of the films. The three layer film PEC-3, which is composed of Na-Alg outer layer deposited on a P4VP/Na-Alg double layer, is characterized by the lowest roughness (Rq = 16.3 nm) and the most hydrophilic surface with a contact angle value of 38.1° among all other films. Its crystallinity index is 0.36, and starts to degrade at 195 °C. It exhibits 130–135% equilibrium swelling capacity in acid buffer and water respectively. PEC-3 is the film with the highest drug loading capacity and drug loading efficiency values of 3.51% and 87% respectively. A cumulative drug release of 65% is obtained from PEC-3 within 24 h in pH = 1.2 buffer solution.

Amphoteric superabsorbent polymer based on waste collagen as loading media and safer release systems for herbicide 2, 4‐D

ABSTRACTAs release formulations, superabsorbent polymers have attracted considerable attentions to reduce herbicide leaching and mitigate contamination. For this purpose, this study dealt with preparation, characterization, and performance test of a novel amphoteric superabsorbent polymer in adsorption and release of 2, 4‐Dichlorophenoxyacetic acid (2, 4‐D) herbicide. LW‐g‐p(AA‐co‐DMDAAC) was successfully synthesized by using leather waste (LW) as raw material and acrylic acid (AA), and dimethyldiallylammonium chloride (DMDAAC) as monomers. Then, the resulting LW‐g‐p(AA‐co‐DMDAAC) was characterized before and after 2, 4‐D sorption by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). In addition, LW‐g‐p(AA‐co‐DMDAAC) with great equilibrium swelling capacity of 3203 g/g in distilled water, 181 g/g in 0.9 wt % NaCl exhibited excellent performance of swelling. Two absorption peaks appeared at pH = 4 and 7 solely when swelling occurred, and the swelling behavior in pH = 7 satisfied the pseudo first‐order kinetic equation. Moreover, the sorbed 2, 4‐D reached at 68 mg/g and showed sustained release cycle of 45 days under acidic or alkaline conditions. Therefore, the sustained release pattern of 2, 4‐D as well as water absorbency made LW‐g‐p(AA‐co‐DMDAAC) suitable and potential candidate for controlling the release of herbicides to improve utilization and reduce environmental pollution. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48480.

Recovery of hydrogel from baby diaper wastes and its application for enhancing soil irrigation management

Improving irrigation management by using hydrogels is an advanced approach for maximizing agricultural land productivity. This experimental study demonstrated the technical feasibility of utilizing superabsorbent polymer recovered from waste baby diapers for increasing water retention in soil and improving irrigation management. After separation, recovery and cleaning of the recycled hydrogel, experimental parametric study was performed. It investigated the swelling capacity and kinetics, de-swelling behavior, and the effects of temperature, salt concentration, and pH on the performance of recycled hydrogel. Red clay soil modified with the recovered hydrogel was used to investigate water retention ability in soil. The swelling capacity increases with time, until it approaches an equilibrium state within about 100 min. At normal conditions, the equilibrium swelling capacity achieves an equilibrium value of 235 g water/g hydrogel. The swelling capacity increases with temperature, while it decreases with increasing pH or salt concentration. The addition of the recycled hydrogel to soil decreases water loss by infiltration and enhances irrigation management and plant growth.

Stomach-Specific Drug Delivery of Clarithromycin Using a Semi Interpenetrating Polymeric Network Hydrogel Made of Montmorillonite and Chitosan: Synthesis, Characterization and In Vitro Drug Release Study.

Purpose: In this study, we aimed to prepare an extended drug delivery formulation of clarithromycin (CAM) based on a semi-interpenetrating polymer network (semi-IPN) hydrogel. Methods: Synthesis of semi-IPN hydrogel nanocomposite made of chitosan (CS), acrylic acid (AA), acrylamide (AAm), polyvinylpyrrolidone (PVP), and montmorillonite (MMT) was performed by free radical graft copolymerization method. Swelling kinetic studies were done in acidic buffer solutions of hydrochloric acid (pH = 1.2), acetate (pH = 4), and also distilled water. Also, the effects of MMT on the swelling kinetic, thermal stability, and mechanical strength of the hydrogels were evaluated. Moreover, in vitro release behavior of CAM and its release kinetics from hydrogels were studied in a hydrochloric acid buffer solution. Results: Fourier transform infrared spectroscopy (FTIR) results revealed that synthesis of semi- IPN superabsorbent nanocomposite and CAM incorporation into hydrogel was performed, successfully. Introducing MMT into hydrogel network not only improved its thermal stability but also increased mechanical strength of the final hydrogel product. Also, in comparison with neat hydrogel (1270 g/g), hydrogel nanocomposite containing 13 wt% MMT exhibited greater equilibrium swelling capacity (1568 g/g) with lower swelling rate. In vitro drug release experiments showed that CS-g-poly(AA-co-AAm)/PVP/MMT/CAM formulation possesses a sustained release character over extended period of time compared with CS-g-poly(AA-co- AAm)/PVP/CAM formulation. Conclusion: In the presence of MMT, the effective life time of drug is prolonged, demonstrating a sustained release property. The reason is that interlinked porous channels within superabsorbent nanocomposite network hinder penetration of aqueous solutions into hydrogel and subsequently cause a slower drug release.

Humic acid embedded chitosan/poly (vinyl alcohol) pH-sensitive hydrogel: Synthesis, characterization, swelling kinetic and diffusion coefficient

In the present research, humic acid (HA) embedded chitosan (CHT)-poly (vinyl alcohol) (PVA) pH-sensitive hydrogels have been synthesized using glutaraldehyde as a crosslinker. The hydrogels were characterized by Fourier-transform infrared (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analysis. The effect of HA content, pH, and temperature on the equilibrium solvent uptake has been investigated. With higher HA contents, the equilibrium swelling capacity increases while lower concentrations of acid cause a decrease in the degree of the swelling. The hydrogels have been found to undergo a number of swelling/deswelling cycles when pH of the swelling medium changes from 1.5 to 11.0. Fick’s law, first-order, and second-order kinetic models were applied to the swelling ratio of hydrogels to explain the mass transfer mechanism and specify swelling kinetic parameters. The swelling parameters such as equilibrium swelling capacity, swelling rate constant, swelling exponent, initial swelling rate, diffusion coefficient, etc., have been evaluated.

Manufacturing of superabsorbent membranes of PVA and rice husk fibres reinforced with nanosilica for agricultural and horticultural applications

ABSTRACTNovel superabsorbent membranes (SMs) consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) originated from rice husk (RH), nanosilica, glutaraldehyde and glycerine (G) were manufactured by a compression moulding process. RHs were used to isolate pure CNCs via mechanical and chemical treatments. RHs were used to improve water retention. These SMs were characterised by Fourier-transform infrared spectroscopy, scanning electron microscopy, mechanical testing and differential scanning calorimetry. SMs showed a greater equilibrium swelling capacity than neat cross-linked PVA. Moreover, the water transport mechanism of all SMs was found to follow Fickian diffusion. SMs exhibited good pH-dependent swelling reversibility and high-water retention capacity, making them more efficient water retention materials. The biodegradability of SMs was evaluated under environmental changes. The biodegradability of SMs was evaluated against environmental changes. The SM was also investigated for antimicrobial activity against pathogenic bacteria such as Candida albicans (fungus), Bacillus subtilis (Gram-positive), Staphylococcus aureus (Gram-positive), Proteus vulgaris (Gram-negative) and Erwinia carotovora (Gram-negative). SMs have been found to act as a useful water reservoir, which may make it useful in agricultural applications.Abbreviation: Novel superabsorbent membranes (SMs) consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) originated from rice husk (RH), nanosilica (NS), glutaraldehyde (GLA) and glycerine (G) were manufactured by a compression moulding process. RHs were used to isolate pure CNCs via mechanical and chemical treatments. RHs were used to improve water retention. These SMs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Mechanical Testing and Differential Scanning Calorimetry (DSC).

Starch-based semi-IPN hydrogel nanocomposite integrated with clinoptilolite: Preparation and swelling kinetic study

Semi-interpenetrating polymer network (semi-IPN) of starch-graft-poly(acrylic acid-co-acrylamide)/polyvinyl alcohol/clinoptilolite (starch-g-p(AA-co-AAm)/PVA/clino) superabsorbent nanocomposite was synthesized by free-radical graft co-polymerization technique in an aqueous solution. Taguchi method was used to optimize the synthesis reaction condition based on the equilibrium swelling capacity of the hydrogels. FTIR, XRD, and SEM analyses were used to study the chemical and structural properties of the hydrogel samples. The equilibrium swelling capacity of the semi-IPN superabsorbent nanocomposite (364.82 g/g) was higher than that of neat hydrogel (286.21 g/g) and in both of them water penetration into hydrogel network occurred through non-Fickian diffusion mechanism. Incorporation of clino into the polymeric matrix not only increased the equilibrium swelling capacity of the hydrogel, but also induced a substantial enhancement in its mechanical strength. Semi-IPN superabsorbent nanocomposite showed reasonable water absorbency under different loads, good salt and pH-sensitive swelling behavior, and better water retention capability, which make it potentially useful for hygiene products.

Characterisation and swelling–deswelling properties of superabsorbent membranes made of PVA and cellulose nanocrystals

ABSTRACTNovel superabsorbent membranes (SMs) consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) originated from rice husk (RH), glutaraldehyde (GLA) and glycerine (G) were manufactured by a compression moulding process. RHs were used to isolate pure CNCs via mechanical and chemical treatments. RHs were used to improve water-retention. Glycerine was used to increase the elasticity of the SMs. These SMs were characterised by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical testing and differential scanning calorimetry (DSC). SMs showed a greater equilibrium swelling capacity than neat cross-linked PVA. Moreover, the water transport mechanism of all SMs was found to follow Fickian diffusion. SMs exhibited good pH-dependent swelling reversibility and high-water retention capacity, making them more efficient water-retention materials. The biodegradability of the SMs was evaluated against environmental changes. The SM was also investigated for antimicrobial activity against pathogenic bacteria such as Candida Albicans (fungus), Bacillus subtilis (G+ Ve), Staphylococcus aureus (G+ Ve), Proteus Vulgaris (G-Ve) and Erwinia Carotovora (G-Ve). The hydrogel membrane has been found to act as a useful water reservoir, which may make it useful in agricultural applications.

Semi-IPN superabsorbent nanocomposite based on sodium alginate and montmorillonite: Reaction parameters and swelling characteristics

Semi-interpenetrating polymer network (semi-IPN) superabsorbent nanocomposite based on montmorillonite (MMT) and sodium alginate (NaAlg)-g-poly(acrylic acid(AA))/polyvinylpyrrolidone (PVP) was synthesized. Chemical structure and surface morphology of the hydrogels were characterized by FTIR, XRD, thermogravimetric analysis (TGA), SEM, and TEM techniques. FTIR results revealed that graft polymerization, PVP interpenetration through hydrogel network, and nanocomposite formation have occurred. The coarse surface of the hydrogels was changed into interlinked porous structures in the presence of MMT. The effect of polymerization variables on water absorbency of the hydrogels was assessed and optimized. Semi-IPN superabsorbent nanocomposite presented higher equilibrium swelling capacity (618.92 g/g) compared with neat hydrogel (521.17 g/g). Swelling behavior of the hydrogels strongly depended on pH values of the solution as well as the type and concentration of saline solution. Semi-IPN superabsorbent nanocomposite possessed good reswelling capability, making it as an efficient water reservoir to supply required water to plants in agricultural applications.