Superabsorbent Polymer Research Articles

Properties and Microstructure of Alkali-Activated Slag Paste Modified by Superabsorbent Polymers

Properties and Microstructure of Alkali-Activated Slag Paste Modified by Superabsorbent Polymers

Toward sustainable menstrual health management: focus on super absorbent polymers

AbstractIn low- to middle-income communities, the lack of affordability of conventional sanitary products during menstrual cycles can cause psychological and health issues, ultimately affecting their quality of life. It is crucial to develop alternative products that are affordable and accessible to all while also promoting menstrual health and hygiene. Super absorbent polymers (SAPs) are a vital component in current disposable sanitary pads and nappies. However, these SAPs are often non-biodegradable and non-biocompatible. Therefore, the use of eco-friendly materials for the production of SAPs is gaining popularity in the hygiene industry, as it offers a means to reduce the carbon footprint and environmental impact associated with traditional SAPs made from non-renewable petroleum-based materials. SAPs made from polysaccharides often have naturally occurring antibacterial properties, making them appealing for commercial applications in sanitary products such as sanitary pads. In addition, the move toward reusable sanitary pads with antibacterial properties can significantly reduce waste generated by single-use products and prevent the growth of bacteria, improving the safety and hygiene of the product. Furthermore, computational modeling and artificial intelligence are now important tools in SAP synthesis, providing advantages such as predicting polymer properties, rationalizing synthesis pathways, and improving quality control. These tools can reduce synthesis costs by eliminating the need for trial-and-error approaches in polymer synthesis, ultimately promoting more affordable products for end users. Overall, these advancements in polymer synthesis and material design can help to create a more sustainable industry and promote menstrual hygiene and product accessibility to those who need it most.

Mechanical testing and engineering applicability analysis of SAP concrete used in buffer layer design for tunnels in active fault zones

Abstract To tackle the challenge of dislocation damage when tunnels traverse active fault zones, this study introduces the concept of using brittle buffer materials for anti-dislocation. Building on this concept, we propose a novel concrete buffer material utilizing large-sized spherical super absorbent polymers (SAP) as a porogen, aimed at ensuring the safety of tunnel structures during active fault dislocations. To investigate the feasibility and superiority of SAP concrete as a buffer material compared to other similar materials, we prepared samples with three different SAP concrete proportions and conducted a series of physical and mechanical tests. The results show that SAP pre-hydrated with 0.2 mol·L−1 sodium carbonate solution exhibits a slower rate of moisture loss in the cement slurry, aiding the hydration reaction of concrete. The permeability coefficient of SAP concrete is approximately 10−7 cm·s−1, slightly lower than foam concrete of the same density level. SAP concrete buffer material demonstrates significant brittleness, in contrast to the mostly ductile nature of other buffers such as foam concrete and rubberized concrete. Utilizing the brittle nature of SAP concrete materials, when applied to tunnels affected by stick–slip active fault dislocations, its instantaneous loss of compressive capacity provides excellent yield performance, thus protecting the tunnel lining from damage. However, under certain circumferential pressure conditions, both the peak and residual strength of SAP concrete significantly increase. High peak and residual strengths do not favor the effective buffering effect of SAP concrete; therefore, an approach involving the intermittent arrangement of precast buffer blocks has been proposed for application.

Effect of Super Absorbent Polymer mixing method on shrinkage performance of cast-in-place concrete confined by existing concrete

Abstract To study the effect of different super absorbent polymer (SAP) mixing methods on mechanical and shrinkage properties of internal curing concrete, SAP mixing mode was used as the study variable, and simulated the bridge leveling structure. The flow performance test, mechanical performance test, free shrinkage test, restrained shrinkage test and scanning electron microscope observation test were carried out on the internal curing concrete. The influence of different mixing methods on the flow properties, mechanical properties, shrinkage properties and microstructure of internal curing concrete were analyzed. The results showed that the amount of mixing water had a great influence on the fluidity when adding pre-absorbent SAP; The effect of SAP on the mechanical properties is minimal when the dosage is 0.2% of the mass of cementing material; Pre-absorbent SAP has the best effect on improving shrinkage cracks of concrete; SAP stored water at the initial stage of hydration, promoted the generation of hydration products, prolong the hydration process, filled the gap inside the concrete, and improved the anti-cracking performance. It is recommended that SAP should be partially pre-absorbed.

Effects of conventional soil and water conservation measures on soil moisture of sloping land in the loess region

Abstract  Traditional soil conservation measures were widely recognized for their excellent ability to promote rainwater infiltration in the loess region. However, little is known about how these measures affect the soil moisture variations under natural rainfall conditions. To compare their effects on soil water content, four different treatments were conducted at runoff plots, i.e., super absorbent polymer amendment (SCR), ridge–furrow rainwater harvesting with plastic mulching (CRP), the same measure with CRP but without mulching (CRN), and flat planting (FSN, control), soil moisture at multiple slope positions and depths were periodically measured. The results showed that in the top 0- to 30-cm soil, SCR and CRN relatively greatly varied with time, yet CRP and FSN changed less. The mean soil water content of these treatments generally followed the pattern of CRN > SCR > CRP > FSN. Responding to a heavy rainfall event, the recharge and depletion rates of soil water storage generally showed similar patterns of SCR > CRN > CRP > FSN in the topsoil, yet in the deeper soil they followed the patterns of CRP > CRN > FSN > SCR. It suggested that SCR and CRN could improve the water accumulation and infiltration performances in the topsoil, and thus may be more suitable for rain-fed crop planting on sloping farmlands of the loess region.

Coaxial electrospun PVA-SAP functional nanofibers embedded with betel leaf extract for enhanced germicidal activity and breathability

This study investigates the formation of coaxial electrospun nanofibrous membrane with enhanced germicidal activity and breathability using superabsorbent polymer and polyvinyl alcohol integrated with betel leaf extract and its utilization for developing performance textiles. The functional nanofibrous membrane was fabricated through the coaxial electrospinning technique and characterized for the intended applications. The morphological investigation of the developed nano-membrane using scanning electron microscopy revealed the formation of regular nanofibers with diameters ranging from 154 to 200 nm. The FTIR spectra suggested the existence of functional compounds in the nanofibers from their characteristic peaks. The presence of the bioactive compounds in the ethanolic extract of betel leaf was explored using phytochemical screening. The analysis of antibacterial activity against S. aureus and E.coli using the agar disc diffusion method showed an enhanced zone of inhibition with a maximum dimension of 27 mm and 24 mm against S. aureus and E.coli, respectively. The developed coaxial nanofibrous membranes also demonstrated acceptable particle barrier performance with greater than 95 % efficiency and a superior tensile strength of 99.5 N. Besides, the improved moisture management and air permeability of coaxial nano-membranes embedded with betel leaf extracts suggested an easy transfer of fluid and moisture vapor from the body to the environment via the membrane. Hence, the improved germicidal activity with acceptable particle filtration efficiency and enhanced breathability of the developed coaxial electrospun nano-membranes indicated their potentiality of utilizing them in designing performance textiles with simultaneous barrier performance and breathability for comfort.

Design and manufacture of new hybrid hydrogel and superabsorbent polymer for controlled release of fulvic acid based on grafted xanthan gum/gelatin using electron irradiation and its use in fodder corn cultivation

A humic acid-gelatin (HA-Gel) hydrogel, a gallic acid-xanthan gum (GA-XG) hydrogel, a HA-Gel/GA-XG hydrogel, and superabsorbent polymer (SAP) of HA-Gel/GA-XG/polyacrylamide (PAM) hydrogel were synthesized using electron beam irradiation method. The capability of synthesized hydrogels in loading and controlled release of fulvic acid (FA) was studied. The chemical and physical structure of sorbents was confirmed by various analyses. The effect of irradiation dose on mechanical properties, gel percentage, swelling, and absorbency under load (AUL) of the sorbents was investigated. By changing the hydrogel structures into the SAP form, its swelling capacity was increased from 37 to 320 g/g. Both hybrid hydrogel and SAP were reusable for up to 7 cycles. The maximum fertilizer loading capacities for SAP and hybrid hydrogel were 402.1 and, 175.5 mg g−1, respectively. In comparison to hydrogels, the SAP showed a slower FA-release performance. Thus, in soil media, 86 % of FA was released in 15–20 days from the hybrid hydrogel while with the SAP, 81 % of FA was released in 30–35 days. The significant improvement in the growth of fodder corn treated with FA-loaded SAP in the greenhouse media in comparison to the control groups showed the effective performance of the designed SAP, favoring its practical applications.

Adjustment of phase change temperature using KCl to develop composite phase change materials based on super absorbent polymer as carrier for use in building energy conservation

In the present work, a Na2HPO4·12H2O-KCl/SAP composite phase change material (CPCM) adapted to the comfortable indoor temperature of the human body has been successfully prepared. The CPCM was developed by physical mixing of Na2HPO4·12H2O (DSP) as the main PCM, KCl as temperature regulator and super absorbent polymer as carrier. In addition, the CPCM was characterized by various techniques, and its thermal properties were analyzed. The results showed that the phase change temperature (Tm) of DSP could be adjusted from 35.8°C to 32.7°C by KCl and the DSP-KCl mixture containing 4% KCl had a high enthalpy value (241.5 kJ·kg-1). The cooling curve test found that adding 0.75% nano-α-Al2O3 as nucleating agent could greatly reduce the supercooling degree of DSP-KCl mixture to 3.39°C. Adding 14% SAP into the mixture can solve the leakage and reduce the supercooling degree and thermal conductivity. The resulting CPCM with 14% SAP added had appropriate Tm (26.9°C), high enthalpy value (153.5 kJ·kg-1), low supercooling degree (1.34°C) as well as thermal conductivity (0.3079 W·K-1·m-1) and excellent thermal reliability. These results indicated that the CPCM was suitable for the field of building energy conservation.

Influence of type and particle size of superabsorbent polymer on early water distribution and internal curing zone properties of cement paste

The types of commercial superabsorbent polymer (SAP) mainly include ionic-SAP acrylic acid (AA) and nonionic-SAP acrylamide-acrylic acid copolymer (AM), which have different particle sizes due to the limited preparation methods. This study used 1H low-field NMR to clarify the influence of type and particle size of SAP on the water distribution of cement paste. Backscattering electrons and nanoindentation were used to quantitatively analyze the area, porosity, and micromechanical properties of internal curing zone. Finally, void system analysis, compressive strength, and autogenous shrinking were systematically studied. The results indicate that the water absorption and retention capacity of AM in cement paste increase with the increase of particle size, and the area of internal curing zone also increased. As the area of internal curing area increases, the autogenous shrinkage of cement paste significantly decreases. The internal curing effect reduces the unhydrated cement content and increases the high-density C–S–H content of internal curing zone, thereby improving the micromechanical properties and to some extent offsetting the decrease in mechanical properties caused by voids. However, larger particle size AM forms larger void and higher air content, leading to a further decrease in strength. Ionic-SAP AA releases a large amount of water before final setting, weakening internal curing effect and reducing the area of internal curing zone. In addition, the early release of water leads to an increase in the local water-cement ratio, which increases the porosity and low-density C–S–H content of internal curing zone, thereby reducing the micromechanical properties.

Self‐healing characteristics of superabsorbent polymers in epoxy coating for corrosion inhibition of carbon steels

AbstractThis study evaluated the self‐healing characteristics of superabsorbent polymers (SAP) in epoxy polyamide paint systems applied using brush application. The SAP underwent preliminary characterization to determine its primary properties and was then incorporated into the epoxy primer at different percentages. The epoxy‐SAP coating systems then underwent various tests to evaluate their self‐healing capability. Excellent adhesion is obtained with the coating system composed of initial epoxy primer, epoxy‐SAP layer, final epoxy primer, and an epoxy enamel topcoat. Electrochemical impedance spectroscopy (EIS) reveals that the addition of SAP increased the charge transfer resistance and pore resistance and decreased the double layer capacitance of the coating system in a span of 5 h, confirming the self‐healing of the coating. Maximum corrosion protection for 5 h is obtained between 15 to 20 wt% SAP. Lastly, it is determined through long‐term immersion tests that the addition of SAP in the coating significantly decreases the rust formation; however, the coating starts to peel off due to the swelling of SAP after 2–3 days.

Cracking behaviour of concrete with superabsorbent polymer (SAP) under rolling fatigue load and temperature coupling

ABSTRACT To explore the long-term crack resistance of pavement concrete containing superabsorbent polymer (SAP), a fatigue test was designed with the consideration of rolling fatigue load and temperature coupling. The four-point fracture and acoustic emission tests were combined to evaluate the evolution of crack resistance. Additionally, the enhancement mechanism was revealed through scanning electron microscopy and mercury intrusion porosimetry experiments. The results indicate that the coupling effects of rolling fatigue load and temperature accelerate the deterioration of the fracture performance of concrete, particularly the freeze–thaw conditions. The concrete with SAP had greater fracture toughness, with improvements of 9.3%, 11.9%, and 58.1% under the coupling rolling fatigue loading and high temperatures, low temperatures, and freeze‒thaw cycles, respectively. The fracture process of concrete with SAP includes fluctuation, fatigue accumulation, and fatigue failure periods, and the SAP delays the arrival time of cumulative ring count and energy, significantly reducing the rate of concrete damage. More fibrous C-S-H and ettringite were generated at the interface microcracks in the concrete containing SAP, confirming the greater degree of hydration. Moreover, the SAP reduced the porosity and average pore size, which enabled the concrete to better resist the impact of rolling fatigue loading and adverse environmental temperatures.

Rheology of Superabsorbent Polymer-Modified and Basalt Fiber-Reinforced Cement Paste with Silica Fume: Response Surface Methodology

A composite's rheology can be changed by adding superabsorbent polymer (SAP) and basalt fibers and using silica fume. This study aimed to investigate the effects of these components on the viscosity and shear stress parameters of the paste. The proportions of the components were varied, with SAP content ranging from 0.01% to 0.03%, basalt fiber from 0% to 0.50%, silica fume (micro silica) at 15%, and water content from 0.40 to 0.50. Response surface methodology was used to optimize the mixture proportions, and the rheological properties of the resulting pastes were characterized using a rheometer. Results showed that the addition of SAP and basalt fiber had a significant impact on the rheological properties of the paste, with increasing amounts of both resulting in increased viscosity and shear stress. Overall, this study highlights the potential of SAP and basalt fiber in advances of the rheology of cement paste and provides insight into the optimal proportions of these components for achieving desired rheological properties. The findings of this study could be useful in developing high-performance concrete with enhanced rheological properties, which could have a wide range of applications in the construction industry. In addition, 0.50% BF, 0.01% SAP, and 0.445 water-to-cement were found as optimum proportions regarding the rheology of the cement paste.

Role of superabsorbent polymer in compression behavior of high water content slurries

Role of superabsorbent polymer in compression behavior of high water content slurries

Dual-function highly oxidative potassium salts empowering high-performance transition metal oxide/activated carbon for hybrid aqueous supercapacitors

In this work, a novel strategy of high-temperature oxidation-activation followed by rapid low-temperature aqueous-reflux treatment is developed to prepare transition metal oxide-activated carbon (TMO-AC) composites for supercapacitor applications. The super-absorbent polymer is selected as the carbon source, and the highly oxidative potassium salts K2FeO4/KMnO4 serve as both precursors for TMO and activators for AC. AC possesses a well-developed porous structure. Moreover, TMO grows uniformly in-situ on AC surface and displays a small size below 10 nm. The prepared Fe2O3-ACFe and MnO2-ACMn composites exhibit remarkable specific capacitance of 645.0 and 548.0 F g−1, respectively. Hybrid aqueous supercapacitors are assembled with Fe2O3-ACFe and MnO2-ACMn as negative and positive electrodes, respectively. A stable operating voltage of 1.2 V is achieved in the KOH electrolyte, resulting in a remarkable 90.2% capacitance retention over 10,000 cycles. Furthermore, in the Na2SO4 electrolyte, a wide 1.6 V voltage window is obtained, contributing to a substantial energy density of 49.35 Wh kg−1. This work provides an interesting approach for the fabrication of high-performance TMO-carbon composite electrodes.

Superabsorbent Polymers Cross-linked with AlCl3: Synthesis, Characterization, and Potential for Sustainable Agriculture

Superabsorbent Polymers Cross-linked with AlCl3: Synthesis, Characterization, and Potential for Sustainable Agriculture

Using superabsorbent polymer to mitigate the fast setting and high autogenous shrinkage of carbide slag and sodium silicate activated ultrafine GGBS based composites

Alkali-activated GGBS based composite is a low carbon engineering material, but limited by some unavoidable disadvantages, such as fast setting and high autogenous shrinkage. In present work, superabsorbent polymer (SAP), which was synthesized by copolymerizing acrylic acid and acrylamide, was used to control the setting time and autogenous shrinkage of carbide slag and sodium silicate activated ultrafine GGBS based composites (CSGC). Results indicated that the fast setting of CSGC was effectively controlled by the addition of SAP. The initial and final setting time were delayed by more than 30 min and 60 min respectively, which provides the possibility to ensure the on-site construction operation. Although SAP mitigated the fast setting of CSGC, it had a negligible effect on the heat release during hydration. Autogenous shrinkage was reduced by 27% when only 0.1% SAP was added, and the compensation of autogenous shrinkage became more pronounced with the increased SAP dosage. The amount of large capillary pores above 100 nm was significantly increased in CSGC incorporating high SAP dosage, which leads to a decline in compressive strength. However, the compressive strength of CSGC with low SAP dosage can match that of reference group at 28 d, due to the internal curing effect of released water from SAP.

Investigation of type, size, and dosage effects of superabsorbent polymers on the hydration development of high-performance cementitious materials

The low water-to-binder ratio commonly used for high-performance cementitious materials is known to limit the degree of hydration of their cement particles. This issue often cannot be resolved with conventional external curing methods, primarily because of the low permeability of such materials. Thus, internal curing methods are devised to improve the degree of hydration and maximize the use of cement particles. Focusing on superabsorbent polymers (SAPs) as one of the main internal curing agents, this study investigates the effects of various types, sizes, and dosages of SAPs on the hydration kinetics of high-performance cementitious mixtures. For this purpose, the main performance characteristics of SAPs were characterized first. Paired with monitoring the temperature development patterns in a set of SAP-contained mixtures, thermogravimetric analyses (TGA) and X-ray diffractometry (XRD) investigations were systematically performed to measure the phase consumption of cement particles. Scanning electron microscope (SEM) image analyses were then employed to assess the materials deposited in the remaining SAP voids. By providing original insights into the hydration development process, this study’s outcome guides the use of SAPs with the ultimate goal of maximizing the hydration degree of cement particles, paving the way to minimizing the carbon footprint of high-performance cementitious materials.

Draft genome sequences of Chryseobacterium sp. MHB01, Rhodococcus qingshengii MHB02, and Agrobacterium tumefaciens MHB03 isolated from superabsorbent polymer granules inoculated with an arbuscular mycorrhizal fungus.

Chryseobacterium sp. MHB01, Rhodococcus qingshengii MHB02, and Agrobacterium tumefaciens MHB03 were isolated from superabsorbent polymer granules cultured with an arbuscular mycorrhizal fungus. Whole-genome sequencing of these three strains revealed genome sizes of 4.57 Mb, 7.13 Mb, and 5.49 Mb with G + C contents of 36.9%, 62.5%, and 58.2%, respectively.

Development and performance verification of a water-retaining semi-flexible pavement material based on alkali-activated slag system incorporating superabsorbent polymers

Water-retaining semi-flexible pavement (WRSFP) can effectively mitigate the urban heat island (UHI) effect by reducing the pavement temperature through water evaporation. To reduce environmental impacts and enhance the water retaining capacity and mechanical properties of WRSFP, this paper investigated the effect of proportion of water-retaining grout (WRG) on workability of fresh WRG, compressive strength, flexural strength, and water absorption of hardened WRG based on alkali-activated slag (AAS) system. The optimal proportion of WRG was recommended. The microstructure of the hardened WRG was observed with a scanning electron microscope (SEM), which allowed for a better characterization and understanding of the degree of hydration and mechanical properties of WRG. The WRSFP specimens (WRSFP-20%, WRSFP-25% and WRSFP-30%) with different porosities of porous asphalt mixture (PAM) were tested for moisture susceptibility, rutting resistance and low-temperature cracking resistance. WRSFP-25% had the best moisture resistance and rutting resistance, and the worst low-temperature cracking resistance. The maximum difference of upper surface temperature between WRSFP and stone mastic asphalt (SMA), which is commonly used in pavement, was 13.3 °C. The time to reach 60 °C on the upper surface of WRSFP was 3.4 times longer than that of SMA, which showed an excellent cooling effect of WRSFP.

Dalbergia nigra (Vell.) grown using hydrogel planting methods in the establishment of a silvopastoral system in a degraded soil

This work tested the use of a superabsorbent polymer (hydrogel) in a silvopastoral system with Brazilian-rosewood (Dalbergia nigra (Vell.) Allemão ex Benth.) in a degraded pasture area. The experimental site is part of the Bananal do Norte experimental farm, Cachoeiro de Itapemirim, Espírito Santo, Brazil. Over 480 seedlings were planted and submitted to the treatments: Dry hydrogel (DRY); Hydrated hydrogel around the root ball (HAR); Hydrated hydrogel mixed with soil (HMS); and water only (WAT). The design was in randomized blocks, with three repetitions. The tested variables were plant survival, height and root collar diameter until 672 days after planting, soil moisture at 93 days after planting and total biomass and leaf chemical analysis at 184 days after planting. Survival was positively influenced by the application of the hydrogel, but there was little or no effect regarding the application method. The hydrogel and its application techniques did not alter growth in height and root collar diameter. The polymer did not influence the development in biomass and nutritional content of the leaves, but did influence the biomass distribution. The use of the superabsorbent polymer was therefore not effective in accelerating plant growth and anticipating the stages in the implantation of the silvopastoral system.
 Keywords: agroforestry, brazilian-rosewood, degraded pasture.