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A novel bio-based crosslinker – epoxidized succinic acid (ESA)—was prepared from the condensation reaction of succinic acid with epichlorohydrin. The ESA was used as a surface-crosslinker to improve the low gel strength of itaconic acid-based superabsorbent polymers (SAPs). The surface-crosslinked SAP showed a significant improvement in absorbency under loads of up to 220%, and its storage modulus increased by ~ 12 times compared to that of an untreated SAP. The proper balance of absorption performance was optimal when the acetone:DW volume ratio of the surface-crosslinking solution was 8:2. The bio-based content of the optimal SAP was enhanced up to 59.7%. [ABSTRACT FROM AUTHOR]

Herein, the absorption properties of a superabsorbent polymer (SAP) are enhanced by preparing a lightly crosslinked poly(itaconic acid-co-acrylic acid) via solution copolymerization with 1,6-hexanediol acrylate as the crosslinker and ammonium persulfate as the initiator, then adding a surface-crosslinked shell containing a nanoclay. The structures of the CSAP and surface-crosslinked SAP are characterized using FT-IR spectroscopy and XRD analysis. The analysis in absorption properties according to nanoclay are evaluated. In addition, the gel strength and thermal stability are evaluated. The introduction of nanoclay in the surface layer is thereby shown to improve the absorption properties and thermal stability of the SAP. [ABSTRACT FROM AUTHOR]

The improvement of gel strength and absorption properties through the surface-crosslinking of superabsorbent polymers (SAPs) is essential for sanitary industry applications. We prepared core-SAP via aqueous solution copolymerization, and then surface-crosslinked the core-SAP under various conditions. The structure of the SAP was characterized using Fourier transform infrared (FT-IR) spectroscopy. Central composite design (CCD) of response surface methodology (RSM) has been applied to determine the optimum surface-crosslinking conditions such as surface-crosslinker content, reaction temperature, and reaction time. The optimal surface-crosslinking conditions were identified at a surface-crosslinker content of 2.22 mol%, reaction temperature of 160 °C, and reaction time of 8.7 min. The surface-crosslinked SAP showed excellent absorbency under load of 50 g/g with a permeability of 50 s. Other absorption properties were also evaluated by measuring the free absorbency and centrifuge retention capacity in saline solution. [ABSTRACT FROM AUTHOR]

An elaborate surface‐crosslinking method was introduced to enhance the low absorbency under load (AUL) and liquid permeability of itaconic‐acid‐based superabsorbent polymer (SAP). The effects of the surface‐crosslinking reaction parameters of the absorption properties of the SAP were investigated. An increase in the content of distilled water and 1,4‐butanediol used as the surface‐crosslinking solution improved the AUL and liquid permeability of the SAP, whereas an increase in the distilled water content resulted in a sharp decrease in the centrifuge retention capacity (CRC) of the SAP. Therefore, controlling the content of 1,4‐butanediol is an effective strategy to improve the AUL while maintaining the CRC of the SAP to some extent. Increasing the surface‐crosslinking temperature tends to decrease the CRC of the SAP. The AUL of the SAP is the highest at a reaction temperature of 160 °C. As a result, the SAP prepared under optimal surface‐crosslinking conditions showed a CRC, AUL and liquid permeability of 36.0, 27.2 g g–1 and 80 s, respectively. The cell viability and cytotoxicity of the SAP on human dermal fibroblasts were confirmed using a live/dead assay and the adapted method from the ISO 10993‐5 protocol. These investigations suggested that itaconic‐acid‐based SAPs could be potential materials for diaper products. © 2022 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The polymerization of itaconic acid is generally characterized by a slow polymerization rate and poor network formation. This results in a polymer with low absorption properties. To improve absorption properties and for use in the hygiene industry, we have been researching superabsorbent polymers (SAPs) based on itaconic acid precursors. In this study, poly(itaconic acid-co-acrylic acid) composites using cellulose, a natural polymer, were synthesized by aqueous solution polymerization, and the surface-crosslinking of the SAP composites was introduced. We characterized the structure of SAP composites using Fourier transform infrared (FT-IR) spectroscopy. We also measured absorption properties such as centrifuge retention capacity (CRC), absorbency under load (AUL), and permeability in 0.9 wt.% saline solution. We confirmed the synthesis conditions of SAP composites by crosslinker type, cellulose content, and surface-crosslinking conditions. We found the best performance of an SAP with a CRC of 27.8 g/g, AUL of 21.1 g/g, and permeability of 61 s at 5 g input cellulose. In addition, surface characteristics were evaluated by scanning electron microscopy, and thermal stabilities were analyzed by thermo gravimetric analysis. [ABSTRACT FROM AUTHOR]

The improvement of gel strength and absorption properties through the surface-crosslinking of superabsorbent polymers (SAPs) is essential for sanitary industry applications. We prepared core-SAP via aqueous solution copolymerization, and then surface-crosslinked the core-SAP under various conditions. The structure of the SAP was characterized using Fourier transform infrared (FT-IR) spectroscopy. Central composite design (CCD) of response surface methodology (RSM) has been applied to determine the optimum surface-crosslinking conditions such as surface-crosslinker content, reaction temperature, and reaction time. The optimal surface-crosslinking conditions were identified at a surface-crosslinker content of 2.22 mol%, reaction temperature of 160 °C, and reaction time of 8.7 min. The surface-crosslinked SAP showed excellent absorbency under load of 50 g/g with a permeability of 50 s. Other absorption properties were also evaluated by measuring the free absorbency and centrifuge retention capacity in saline solution.

The purpose of this study is to improve the low absorbency under load and the permeability of a superabsorbent polymer (SAP)-based on itaconic acid by introducing a polycationic salt into the core-SAP to form ionic bonds as well as by adding modified silica to the surface-crosslinked SAP. The core-SAP was synthesized by aqueous polymerization using itaconic acid, vinyl sulfonic acid, and tetra (ethylene glycol) diacrylate. The absorbency under loading of the core-SAP was improved using aluminum sulfate and zirconium sulfate as polycationic salts. The surface-crosslinked core-SAP with the modified silica showed increased permeability. [ABSTRACT FROM AUTHOR]

A superabsorbent polymer (SAP) is a special polymer material that can absorb up to 500 times its own weight of pure water, but has a problem that it does not biodegrade itself and cause environmental pollution. Therefore, we aim to prepare a biodegradable SAP by using biomass‐based IA. The SAP must be able to retain absorbed water and absorb water under a given pressure. We have carried out studies to improve the surface hardness of the SAP to enhance absorption of water under a given pressure by surface‐crosslinking. Four types of surface‐crosslinkers, ethylene glycol diglycidyl ether (EGDGE), ethylene carbonate (EC), 1,4‐butanediol (BD), or glycerol, were used. We confirmed the water absorption capacity of the SAP by measuring its centrifuge retention capacity (CRC) and absorbency under load (AUL). The structural characteristics of the SAP were confirmed by attenuated total reflection (ATR) and X‐ray photoelectron spectroscopy (XPS), and the surface characteristics were confirmed by scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

Herein, core-superabsorbent polymer (CSAP) composites are prepared from oxidized starch (OS) via aqueous solution copolymerization using ammonium persulfate as the initiator, and 1,6-hexanediol diacrylate as the inner-crosslinker. The surface-crosslinking process is performed using various surface-crosslinkers, including bisphenol A diglycidyl ether (BADGE), poly(ethylene glycol) diglycidyl ether (PEGDGE), ethylene glycol diglycidyl ether (EGDGE), and diglycidyl ether (DGE). The structures of the CSAP composites and their surface-crosslinked SAPs (SSAPs) are characterized using Fourier transform infrared (FT-IR) spectroscopy, their absorption properties are measured via centrifuge retention capacity (CRC), absorbency under load (AUL), permeability, and re-swellability tests, and their gel strengths according to surface-crosslinker type and EGDGE content are examined via rheological analysis. The results indicate that an EGDGE content of 0.75 mol provides the optimum surface-crosslinking and SSAP performance, with a CRC of 34.8 g/g, an AUL of 27.2 g/g, and a permeability of 43 s. The surface-crosslinking of the CSAP composites using OS is shown to improve the gel strength, thus enabling the SAP to be used in disposable diapers.

In this study, a superabsorbent polymer (SAP) comprising poly (IA-co-cellulose-co-VSA-co-AA; ICVA) core-SAP (CSAP) was synthesized through radical polymerization using itaconic acid (IA), acrylic acid (AA), cellulose, and vinyl sulfonic acid (VSA) as monomers. The absorption performances and relative biodegradability of various compositions prepared by adjusting the amounts of cellulose and VSA with constant IA and AA content were compared. Increasing the cellulose content in CSAP contributed to improved biodegradation of the surface-crosslinked SAP (SSAP) and gel strength, although the free absorbency (FA) and centrifuge retention capacity (CRC) decreased. Increasing the VSA content resulted in strong anionicity, which enables the absorption of large amounts of water. Surface-crosslinking technology was applied to the CSAP synthesized with the optimal composition ratio to increase its absorption performance and gel strength. Improved performance of the synthesized SSAP (a CRC of 30.4 g/g, absorbency under load (AUL) of 23.3 g/g, and permeability of 55 s) was achieved by selecting the optimal surface-crosslinking treatment time and the amount of distilled water in the surface-crosslinking solution: as the latter was increased in the surface-crosslinking solution, the AUL and permeability of the SSAP were improved, and its biodegradability was found to be 54% compared to the 100% biodegradable cellulose hydrogel in the control group.

Herein, core-superabsorbent polymer (CSAP) composites are prepared from oxidized starch (OS) via aqueous solution copolymerization using ammonium persulfate as the initiator, and 1,6-hexanediol diacrylate as the inner-crosslinker. The surface-crosslinking process is performed using various surface-crosslinkers, including bisphenol A diglycidyl ether (BADGE), poly(ethylene glycol) diglycidyl ether (PEGDGE), ethylene glycol diglycidyl ether (EGDGE), and diglycidyl ether (DGE). The structures of the CSAP composites and their surface-crosslinked SAPs (SSAPs) are characterized using Fourier transform infrared (FT-IR) spectroscopy, their absorption properties are measured via centrifuge retention capacity (CRC), absorbency under load (AUL), permeability, and re-swellability tests, and their gel strengths according to surface-crosslinker type and EGDGE content are examined via rheological analysis. The results indicate that an EGDGE content of 0.75 mol provides the optimum surface-crosslinking and SSAP performance, with a CRC of 34.8 g/g, an AUL of 27.2 g/g, and a permeability of 43 s. The surface-crosslinking of the CSAP composites using OS is shown to improve the gel strength, thus enabling the SAP to be used in disposable diapers. [ABSTRACT FROM AUTHOR]

In this study, a superabsorbent polymer (SAP) comprising poly (IA-co-cellulose-co-VSA-co-AA; ICVA) core-SAP (CSAP) was synthesized through radical polymerization using itaconic acid (IA), acrylic acid (AA), cellulose, and vinyl sulfonic acid (VSA) as monomers. The absorption performances and relative biodegradability of various compositions prepared by adjusting the amounts of cellulose and VSA with constant IA and AA content were compared. Increasing the cellulose content in CSAP contributed to improved biodegradation of the surface-crosslinked SAP (SSAP) and gel strength, although the free absorbency (FA) and centrifuge retention capacity (CRC) decreased. Increasing the VSA content resulted in strong anionicity, which enables the absorption of large amounts of water. Surface-crosslinking technology was applied to the CSAP synthesized with the optimal composition ratio to increase its absorption performance and gel strength. Improved performance of the synthesized SSAP (a CRC of 30.4 g/g, absorbency under load (AUL) of 23.3 g/g, and permeability of 55 s) was achieved by selecting the optimal surface-crosslinking treatment time and the amount of distilled water in the surface-crosslinking solution: as the latter was increased in the surface-crosslinking solution, the AUL and permeability of the SSAP were improved, and its biodegradability was found to be 54% compared to the 100% biodegradable cellulose hydrogel in the control group. [ABSTRACT FROM AUTHOR]

For the application of superabsorbent polymer (SAP) particles in personal hygiene products such as disposable diapers, the SAP surface is additionally crosslinked to minimize gel blocking and enhance absorbency under external pressure. Physically surface-crosslinked poly(acrylic acid)(PAA)-based SAP microspheres were prepared using polycations (branched polyethylene imine (bPEI) and polyamidoamine (PAMAM)). Compared with chemical crosslinking, which requires a high temperature and prolonged reaction, physical crosslinking via electrostatic interaction between the polycations and negatively charged PAA chains was achieved within 20 min at room temperature. The polycation-crosslinked SAP particles had a rougher surface and lower water absorption capacity. The thickness of the physically crosslinked surface, visualized using fluorescence labeled polycations, increased with increasing polycation concentration and reaction time, eventually reaching saturation. PAMAM produced mechanically stronger and thicker surface-crosslinking than bPEI, owing to its lower molecular weight. Micro-CT analysis of the collective swelling behavior of a gel bed packed with the SAP particles confirmed that the shapes of the SAP particles crosslinked with polycations were better maintained during swelling and there was a greater void fraction in the packed gel bed than with the use of bare SAP particles, which might minimize gel blocking and improve the permeability of fluid through gel bed. Unlabelled Image • Surface-crosslinking of PAA-based SAP was performed with polycations via electrostatic interaction. • Surface-crosslinking with polycations was achieved at room temperature within 5 minuntes and could be visualized. • Surface-crosslinking with polycations improved the mechanical properties of SAPs and minimized gel-blocking. [ABSTRACT FROM AUTHOR]