Superabsorbent Polymer Research Articles

Unveiling Superabsorbent Hydrogels Efficacy Through Modified Agronomic Practices in Soybean–Wheat System Under Semi‐Arid Regions of South Asia

ABSTRACTThe sustainability of global agriculture at higher productivity level is a concern owing to climate change, serious environmental footprints, dipping factor productivity and shrinking availability of natural resources, especially. The situation is worsening in the ‘Food Bowl of India’—Indo‐Gangetic plains (IGP) by several amalgamated factors, such as declining groundwater, unpredictable precipitation owing to climate change and cultivation of heavy water duty crops. To neutralise these issues, a field experiment was executed for the period 2019–2021 to assess the efficacy of indigenous hydrogels (P‐hydrogel and Superabsorbent polymer hydrogel‐1118) and their application methods viz., seed treatment, slurry application and soil application on crop yield and water productivity, soil moisture dynamics and profitability in a soybean–wheat cropping system under irrigation and rainfed conditions. In both study years (2019–2020 and 2020–2021), due to higher seed germination percentage, irrigation application together with seed treatment and slurry application of superabsorbent polymer hydrogel‐1118 improved system productivity by 8.1%–26.7% and system water productivity by 17.6%–33.8% over control. Wheat grain yield was enhanced by 8.0% (2019–2020) to 32.2% (2020–2021) due to superabsorbent polymer hydrogel‐1118 hydrogel with 10 cm lesser use of irrigation water compared with control (no‐hydrogel). Soil moisture content in 0–15 cm soil layer was also found higher by 1.8%–2.4% in superabsorbent polymer hydrogel‐1118 and P‐hydrogel slurry‐applied plots. Therefore, higher gross profitability (31.8%), net profitability (89.8%) and B:C (26.9%) in wheat could be attributed to increased crop yields when seeds were treated with superabsorbent polymer hydrogel‐1118. Therefore, the utilisation of modified hydrogel application, in the form of seed treatment (seed coating) and slurry application has demonstrated improvement in seed germination, crop yield and water productivity and made soybean–wheat cultivation more economical. This approach presents a feasible solution to achieving a viable production system of soybean and wheat crops by reducing irrigation amounts in the IGP of India, as well as other comparable ecological places worldwide.

Gamma-Irradiated Gum Arabic Grafted with 2-Hydroxyethyl Methacrylate: A Novel Superabsorbent Polymer for Controlled Folic Acid Release.

This study explores the synthesis and characterization of superabsorbent hydrogels derived from chemically modified gum Arabic, designed for controlled folic acid release. The synthesis involves a two-step process: carboxymethylation followed by grafting with 2-hydroxyethyl methacrylate via gamma irradiation. The resulting hydrogels exhibit enhanced mechanical strength and controlled diffusivity, essential for nutrient delivery systems. Key factors such as copolymer composition and irradiation dose are investigated, affecting the synthesis process. Systematic studies of swelling behaviors reveal that the hydrogel achieves a maximum swelling of 888.1% at 40°C. The hydrogels are loaded with folic acid, and in vitro, sustained release profiles are examined under various pH conditions. The maximum release of 83.3% is observed after 24h at pH 7.0, following a Korsmeyer-Peppas release mechanism. Different characterization techniques, confirm the successful synthesis and unique properties of the superabsorbent hydrogels. Rheological behavior analysis, scanning electron microscopy, and biocompatibility assessments provide a comprehensive understanding of the hydrogel structures. Gamma irradiation ensures a homogeneous network structure, crucial for optimal swelling behavior and mechanical properties. This research highlights the potential of eco-friendly biopolymer hydrogels in precise drug delivery applications, leveraging the safety and process control benefits of gamma irradiation.

Full micro-nanofiber aerogel with three-dimensional fluffy network structure for rapid liquid absorption and uniform liquid retention in diapers

Diapers are essential for infants and patients with urinary incontinence. The super-absorbent polymer (SAP) in the core layer of diapers suffers from slow liquid absorption, fault formation, and reverse osmosis. Therefore, it is desirable to construct a core layer that can integrate rapid liquid absorption, uniform retention, and anti-seepage qualities. In this study, a diaper core layer and a three-dimensional fluffy network structure with a wetting gradient was constructed via one-step solution blow spinning (SBS). By regulating the content of the glutaraldehyde (GA) cross-linking agent, absorbent and insoluble fibers could be obtained. The ratio of super-absorbent fibers (SAF) to PAN-PVP micro-/nano fibers in the three-layer fiber structure and the gram weight of the core layer were adjusted. A wetting gradient was established when the weight of the adjusted gradient core layer was 2/3 that of the commercial core layer. The amount of reverse osmosis was reduced by 0.25 g, and the liquid absorption and retention were 30 times and 28.5 times, respectively, two and 3.5 times higher than those of commercial diapers. The SAF prepared by SBS could improve the core layer's liquid absorption rate, retention ratio, and comfort. The fibers are applicable in diapers, sanitary napkins, and other disposable products.

Effect of Superabsorbent Polymers and Presoaked Coarse Recycled Shale Lightweight Aggregates on Relative Humidity Development in Early-Age Concrete

Self-desiccation-induced shrinkage may result in cracking at an early age, which is averse to the durability of concrete. Internal curing (IC) agents, such as superabsorbent polymers (SAP), are normally used for moisture regulation and shrinkage reduction. In addition, the make-up of recycled shale lightweight aggregate (RSLA) results in a good absorbing capacity, which makes it a potential candidate for IC. In this paper, the synergistic effect of SAP and RSLA on the relative humidity (RH) variation in early-age concrete under sealed conditions is investigated experimentally in terms of the setting time, relative humidity, and autogenous shrinkage. The results indicate that adding SAP and presoaked RSLA can significantly postpone the initial and final setting times. The initial setting time of RSLA30 and SAP06 is delayed by 127 and 171 min, respectively, compared to the benchmark mixture. In addition, increasing the amounts of SAP and presoaked RSLA can effectively extend the duration of the vapour-saturated stage, reducing the decrease in RH and autogenous shrinkage at 28 days. When the RSLA dosage increases from 0 to 10%, 20%, and 30%, the duration of the vapour-saturated stage is extended by 2, 9.4, and 26 days, respectively. Moreover, due to different water desorption behaviours, more IC water released by RSLA during the initial stage can slow the water release of SAP and lead to a higher RH level at 28 days.

Radiation resistance and saturated adsorption capacity of a superabsorbent polymer and anion-supporting hydrogel for the safe storage of treated water

Treated tritium-containing water is stored in tanks at the Fukushima Daiichi Nuclear Power Plant until ocean discharge is completed; however, the risk of leakage and contamination remains. We propose the combination of a superabsorbent polymer and an anion-supporting hydrogel for the safe and long-term storage of this water. The external radiation resistance of these materials in the presence of water was investigated, and their water absorption and Cs+ and I retention capacities following irradiation to a cumulative absorbed dose of up to 40 Gy were determined. The superabsorbent polymer demonstrated good water retention and Cs+ adsorption capability. The saturated I adsorption capacity of the hydrogel was 575 ± 28 mg/g, and maintained up to an absorbed dose of 100 Gy. The proposed method can be implemented until the planned completion of water processing even if the storage location has a dose rate of 100 µGy/h.

Investigation of the Compressive Strength and Void Analysis of Cement Pastes with Superabsorbent Polymer.

This study aimed to experimentally investigate the compressive strength and air voids of cement pastes with varying dosages of Superabsorbent Polymer (SAP) and water-to-cement (w/c) ratios. Cement pastes were prepared using three different w/c ratios of 0.4, 0.5, and 0.6, along with different dosages of SAP ranging from 0.2% to 0.5% by weight of cement. Additionally, SAP was introduced in two forms: dry and wet. After casting the cubes, two distinct curing conditions were employed: curing at a temperature of 20 °C with a Relative Humidity (RH) of 60% (Curing 1), and water curing (Curing 2). The results revealed that the addition of SAP increased early strength when subjected to Curing 1, followed by a decrease in later strength. On the other hand, samples with SAP and water curing exhibited higher strength compared to those without SAP, especially with w/c ratios of 0.4 and 0.5. However, at a w/c ratio of 0.6, nearly all samples showed a reduction in strength compared to those without SAP. Furthermore, air void analysis was performed on all samples cured for 28 days using an image analysis technique. The samples containing wet SAP resulted in a higher total air content compared to the samples with dry SAP. Additionally, the incorporation of wet SAP in cement paste led to lower specific surface areas and a higher spacing factor than the samples with dry SAP. These findings suggest that the clumping of wet SAP particles during presoaking resulted in coarser air voids compared to the samples containing dry SAP.

Modification of fresh and hardened properties of 3D-printed recycled mortar by superabsorbent polymers

The high water absorption level of recycled sand limits the applicability of 3D-printed recycled mortar. In this study, superabsorbent polymers (SAPs) were adopted to modify the properties of both fresh and hardened 3D-printed recycled mortar. The effects of various SAP dosages, particle sizes, and addition methods were carefully examined. X-ray diffraction (XRD) and computed tomography (CT) were adopted to observe the microstructure. The test results showed that the addition of SAP effectively improved the printability of the mixed mortar. Particularly, with the addition of SAP, the autogenous shrinkage was reduced by more than 50 %, indicating that the polymer had an obvious inhibitory effect on shrinkage. Furthermore, the hydration of cementitious materials was promoted, resulting in an increase in compressive strength by 27%–69 %. Microstructural analysis further confirmed that the addition of SAP optimized the pore structure and enhanced the density of the 3D-printed mortar but did not change the types of hydration products. Generally, for the modification of 3D-printed mortar with recycled sand, it would be recommended to add SAP at a doping level of 0.4 % with a particle size of 60–100 mesh.

Assessing seed pellet formulations to improve native plant restoration under water‐limited conditions

Water scarcity, a challenge expected to worsen with climate change, significantly hinders native plant community restoration. Enhancing seed‐based restoration requires methods to increase the water availability for seeds and seedlings. Surfactants and superabsorbent polymers (SAPs) can improve soil water‐holding capacity and infiltration, but their use in seed enhancements remains underexplored. We investigated whether pellets containing surfactants or SAPs could improve seedling emergence of two native species (Rytidosperma caespitosum and Chrysocephalum apiculatum) common in temperate grasslands in south‐eastern Australia under different watering treatments. We used a randomized block design with five watering treatments to simulate predicted changes in precipitation for south‐eastern Australia: ambient, two reducing overall water volume, and two reducing watering frequency while increasing watering volume to maintain ambient treatment water volume. We explored four enhanced pellets (two containing surfactants and two containing SAPs) and non‐pelleted seeds. Our results showed that watering events with larger volumes but reduced frequency increased seedling emergence. Under these conditions, block co‐polymer surfactants further increased seedling emergence of C. apiculatum, while synthetic SAP pellets promoted emergence of R. caespitosum. Block co‐polymer surfactants decreased R. caespitosum emergence, and both SAPs reduced C. apiculatum emergence under reduced watering frequency. A 50% reduction in overall water volume significantly reduced seedling emergence for both species, regardless of seed enhancement. These findings suggest that surfactants and SAP pellets can improve the success of seed‐based restoration under ambient conditions and when rainfall events are larger in volume but reduced in frequency, but not when the overall volume of rainfall is reduced.

Durability performance of superabsorbent polymer incorporated concrete modified by nano-silica addition in seasonal frozen regions

In seasonal frozen regions, ion erosion and freeze-thaw (F-T) cycles threaten pavement concrete durability. This study evaluates the suitability of superabsorbent polymer (SAP) concrete modified by nano silica (NS) for enhancing durability. Tests were conducted to analyze chloride impermeability and frost resistance effects on modified SAP concrete. The coupling impact of ion erosion and freeze-thawing was also evaluated. Mercury intrusion porosimetry (MIP), scanning electron microscopy, and energy dispersive spectrometry were employed to investigate microstructure characteristics. Results demonstrated that NS-modified SAP concrete exhibited high resistance to ion erosion and F-T cycles. Adding 3 % NS reduced the relative dynamic elastic modulus (RDEM) loss by 23.21 % after 300 F-T cycles. The enhancement was more pronounced under the coupled action of ion erosion and freeze-thawing, and the RDEM loss and scaling quantity per unit area of NS-3 % decreased by 13.21 % and 41.48 % respectively, and compressive strength was 28.33 % higher than that of SAP concrete after 135 salt-frost cycles. MIP testing indicated that 3 % NS significantly improved pore structure, reducing deterioration in much harmful pores by 12.82 %. SAP promoted the efficient pozzolanic reaction of NS, generating high-density C-S-H. Additionally, second-hydration products were adsorbed by the ionization of SAP microgel, densifying its shrinkage voids and delaying ITZ width and micro-crack propagation, thereby enhancing concrete durability.

Improvement of Mechanical Properties of Superabsorbent Polymers by Addition of Cellulose for Flexible Batteries

Improvement of Mechanical Properties of Superabsorbent Polymers by Addition of Cellulose for Flexible Batteries

Influence of the Crosslinker Hydrophobicity on the Swelling Kinetics of Poly(Acrylic Acid) Microgels

AbstractSuperabsorbent polymer gels are widely used in commercial areas, such as in hygiene products. A key aspect in these and other applications is the gel swelling kinetics, and a key factor of influence on that is the hydrophobicity of the gel. This paper reports on the synthesis of superabsorbent polymer microgel particles with four differently hydrophobic crosslinkers: N,N’‐methylenebisacrylamide (MBAA), N,N’‐ethylenebisacrylamide (EBAA), N,N’‐propylenebisacrylamide (PBAA), and N,N’‐butylenebisacrylamide (BBAA). This work uses droplet‐based microfluidics to produce uniform and well‐defined microgel specimen and study the influence of the crosslinker hydrophobicity on the swelling kinetics. In particular, this work determines swelling constants and their dependencies on the temperature of the swelling medium as well as the activation energies of swelling in relation to the crosslinker hydrophobicity. This work finds two competing effects, leading to a narrow window in which the activation energy of the swelling of the microgels decreases with increasing crosslinker hydrophobicity.

Improving the stabilization/solidification performance of Pb-containing alkali-activated slag via incorporation of superabsorbent polymer

Alkali-activated materials (AAM) have garnered significant attention for the treatment of Pb-contaminated solid waste, attributed to their low carbon footprint and superior stabilization/solidification (S/S) capabilities. However, recent concerns arise regarding their long-term S/S performance, especially when exposed to rainwater environments and considering the inherent shrinkage and potential cracking of AAM. This research delves into the feasibility of enhancing the S/S efficacy of alkali-activated slag (AAS) through the integration of super absorbent polymers (SAP). Findings reveal a marked improvement in the S/S performance of Pb-laden AAS upon SAP addition. Specifically, incorporating 0.5 wt% and 1 wt% SAP curtailed Pb leaching in AAS samples (cured for 90 days) by 47 % and 75 %, respectively. Comprehensive analyses using XRD, TGA, MIP, BSEM, EDX, XPS and MAS NMR suggest that the bolstered S/S performance of SAP-augmented AAS is not rooted in alterations to the reaction degree, pore structure, or reaction products of AAS. Instead, it hinges on the innate capacity of SAP to absorb and retain Pb. Leaching tests reveal that, in AAS cured for 90 days, approximately 1.72 mg of Pb ions were retained per gram of SAP. This investigation furnishes a novel vantage point for refining and deploying alkali-activated materials (or other cementitious materials) as effective S/S agents.

Investigating the Impact of Superabsorbent Polymer Sizes on Absorption and Cement Paste Rheology.

This study aims to understand the water retention capabilities of Superabsorbent Polymers (SAPs) in different alkaline environments for internal curing and to assess their impact on the rheological properties of cement paste. Therefore, the focus of this paper is on the absorption capacities of two different sizes of polyacrylic-based Superabsorbent Polymers : SAP A, with an average size of 28 µm, and SAP B, with an average size of 80 µm, in various solutions, such as pH 7, pH 11, pH 13, and cement filtrate solution (pH 13.73). Additionally, the study investigates the rheological properties of SAP-modified cement pastes, considering three different water-to-cement (w/c) ratios (0.4, 0.5, and 0.6) and four different dosages of SAPs (0.2%, 0.3%, 0.4%, and 0.5% by weight of cement). The results showed that the absorption capacity of SAP A was higher in all solutions compared to SAP B. However, both SAPs exhibited lower absorption capacity and early desorption in the cement filtrate solution. In contrast to the absorption results in pH 13 and cement filtrate solutions, the rheological properties, including plastic viscosity and yield stress, of the cement paste with a w/c ratio of 0.4 and 0.5, as well as both dry and wet (presoaked) SAPs, were higher than those of the cement paste without SAP, indicating continuous absorption by SAP. The viscosity and yield stress increased over time with increasing SAP dosage. However, in the mixes with a w/c ratio of 0.6, the values of plastic viscosity and yield stress were initially lower for the mixes with dry SAPs compared to the reference mix. Additionally, cement pastes containing wet SAP showed higher viscosity and yield stress compared to the pastes containing dry SAP.

The Applicat ion of Super Absorbent Polymer in Self-Healing Morta r: The Effect on Mechanical Properties

Super Absorbent Polymer (SAP) were used in various application, including in mortar production. The ability of SAP to absorb a high amount of water made this material become a promising water reservoir in the mortar that can later mitigate micro-cracks in concrete. Besides SAP, a nutrient must be embedded into self-healing mortar to support metabolism in bacteria-based self-healing mortar. However, adding SAP and nutrient was reported to decrease the mechanical properties of the resulting self-healing mortar. Thus, in this research, the modification in the mix design of mortar containing SAP and nutrient were observed. The water to cement ratio was decreased up to 0.3. The amount of SAP and entrained water added is based on its swelling capacity. The swelling capacity of SAP, the workability of fresh mortar, and the compressive strength of mortar were examined. The results show that the swelling capacity of SAP was affected by the pH and the presence of calcium ions in the solution. The higher the pH and the calcium ion in the solution, the lower SAP’s swelling capacity. Applying the modified mortar mix design containing SAP and nutrient proofed to mitigate the reduction in workability and compressive strength of the resulting self-healing mortar.

Study on Adsorption Characteristics and Water Retention Properties of Attapulgite-Sodium Polyacrylate and Polyacrylamide to Trace Metal Cadmium Ion.

The adsorption mechanism of superabsorbent polymer (SAP) can provide theoretical guidance for their practical applications in different environments. However, there has been limited research on the mechanism of attapulgite-sodium polyacrylate. This research aimed to compare the Cd(II) adsorption characteristics and water retention properties of organic-inorganic composite SAP (attapulgite-sodium polyacrylate, OSAP) and organic SAP (polyacrylamide, JSAP). Batch experiments were used to investigate the kinetics of Cd(II) adsorption, as well as the thermodynamic properties and factors influencing these properties. The results show that the Cd(II) adsorption capacity was directly proportional to the pH value. The maximum adsorption capacities of OSAP and JSAP were of 770 and 345 mg·g-1. The Cd(II) adsorption for OSAP and JSAP conformed to the Langmuir and the quasi-second-order kinetic model. This indicates that chemical adsorption is the primary mechanism. The adsorption process was endothermic (ΔH0 > 0) and spontaneous (ΔG0 < 0). The water adsorption ratios of OSAP and SAP were 474.8 and 152.6 in pure water. The ratio decreases with the increase in Cd(II) concentration. OSAP and JSAP retained 67.23% and 38.37% of the initial water adsorption after six iterations of water adsorption. Hence, OSAP is more suitable than JSAP for agricultural and environmental ecological restoration in arid and semi-arid regions.

A clinical observational case series evaluation of a superabsorbent dressing on exudating wounds.

The annual cost to the NHS of managing 3.8 million patients with a wound was estimated in 2020 to be £8.3 billion, of which £5.6 billion was spent on the 30% of wounds that did not heal and £2.7 billion on the 70% of wounds that healed (Guest, 2020). One of the main symptoms associated with chronic 'hard-to-heal' wounds is the production of excess exudate (Atkin et al, 2019). This is due to a prolonged chronic inflammatory response stimulated by a physiological cause. This article describes what exudate is and its importance in the wound healing process, highlighting the consequences of too little or excessive wound exudate associated with any wound. The article goes on to describe a case series observational study involving a range of patients (n=47; 33 male/14 female), aged between 33 and 91 years (mean 67.4 years), with a variety of acute (n=11) and chronic exuding wounds (n=44). In total, 55 wounds of various aetiologies were managed with DryMax Super (a dressing whose design includes superabsorbent polymers) in order to evaluate and report on the absorption and fluid-handling properties of the product.

Effect of superabsorbent polymer on 3D printing characteristics as rheology-modified agent

This study aims to investigate the effects of two superabsorbent polymer (SAP) types, S1 and S2 (with continual absorption and rapid desorption, respectively) as rheology-modified agent on 3D printing characteristics. Three base mixtures were selected with different thixotropic behaviors (i.e., mixtures with high re-flocculation (τfloc), high structuration rate (Athix), and both low τfloc and Athix, respectively). The initial mini-slump flow of 190±10 mm was secured by adjusting superplasticizer (SP) or water demand (increasing w/b by either 0.025 or 0.05). An extrudable region was determined within the range of τfloc (200–890 Pa) and Athix (15–60 Pa/min). The use of the S2 SAP significantly improved extruded performance for mixtures with τfloc higher than 1000 Pa. The use of the S1 SAP without increasing w/b (only with extra SP demand) significantly improved the resistance against plastic collapse for the mixtures with τfloc lower than 300 Pa. The reduction in 28-day compressive strength for printed specimens was correlated with τfloc. A high τfloc value led to inadequate interlayer bond and an increased propensity for surface defects of printed structure. The S2 SAP acted as a rheology-modified agent to reduce τfloc and improved the interlayer bond performance by 10 %-20 %.

Closure to the discussion of “Water distribution characteristics of capillary absorption in internally cured concrete with superabsorbent polymers”

Closure to the discussion of “Water distribution characteristics of capillary absorption in internally cured concrete with superabsorbent polymers”

The Combination Between Super Absorbent Polymers (SAPs) and Biofertilizers Could be an Ecofriendly Approach for Soil Chemical Properties Improving and Sustainable Wheat (Triticum Sativum) Production in Sandy Loam Soil

Sustainable agriculture aims to provide food needs while improving soil health and protecting it from degradation and contamination from excessive chemical fertilizer use. Sandy-textured soils have low fertility and water-holding capacity. This study assessed the integrated impact of super absorbent polymers (SAPs) and biofertilizer application on the soil chemical characteristics and wheat growth parameters in sandy loam soil. Two super absorbent polymers (SAPs) included Barbary plant G3 (P1) and Aqua Gool polymer (P2), and four microbial inoculations (Trichoderma harzianum (T), Actinomycetes (Streptomyces rochei and Streptomyces atrovirens) (AC1 and AC2), and Bacillus subtilis (B)) as biofertilizers were used in our pot experiment. The SAPs were applied to soil at a level of 0.2% (w/w), while biofertilizers were applied in the form of microbial cell suspensions (50 ml per pot) in addition to treating wheat seed with these suspensions during cultivation. Wheat plants were irrigated every 8 days to field capacity level. Amending soil with super absorbent polymers and microbes either individually or in combination significantly reduced pH and EC, increased organic matter level, and the availability of macro- and micronutrients in soil. Wheat growth metrics, including shoot length, tiller number, biomass accumulation, leaf area, and grain yield, exhibited considerable enhancements relative to the plants of the control treatment. The interaction between P1 polymer and Streptomyces atrovirens (AC2) showed the highest performance in improving the almost studied parameters. The application of SAPs with microbial biofertilizers offers a promising eco-friendly method for enhancing soil health and wheat yield.

Discussion of “Water distribution characteristics of capillary absorption in internally cured concrete with superabsorbent polymers”

In March 2024 Construction and Building Materials published “Water distribution characteristics of capillary absorption in internally cured concrete with superabsorbent polymers”, which claims to present a water distribution model characterising the spatiotemporal moisture content evolution in internally cured concrete with superabsorbent polymers during capillary absorption. This discussion, considered a post-publication critique, establishes that the paper’s water distribution model conflicts with the paper’s capillary absorption tests. While the model is based on the premise of the square-root-of-time behaviour of capillary absorption, the tests do not demonstrate that square-root-of-time behaviour. This critique in addition questions the paper’s forthright application of the power-law diffusivity expression with exponent 4, given that its validity for the paper’s materials has not been verified. It is shown that different but equivalent diffusivity expressions lead to different moisture diffusivities at lower moisture contents.