Novel Surface Crosslinker for Superabsorbent Polymers Based on Schiff Base Reaction

ABSTRACT Superabsorbent surface modification significantly enhances hydrogels' structure, properties, and functionality, which cannot be directly polymerized. Over the past few decades, this modification technique has broadened the range of applications for superabsorbents in various industries. In this study, the Schiff base compound (E)‐2‐(((4‐hydroxyphenyl)imino)methyl)phenol (HPIMP) was synthesized by reacting salicylaldehyde with para‐aminophenol. The resulting diphenol compound was then transformed into bis (phenol glycidyl ether)imine (DGSB) using epichlorohydrin to create a new crosslinker. The chemical structure of the DGSB crosslinker was analyzed using FTIR and H‐NMR spectroscopies. The results from both FTIR and 1 H‐NMR confirmed that the crosslinker was successfully synthesized. Then, the synthesized DGSB crosslinker (different amounts) as an external crosslinker was used to modify the sodium polyacrylate superabsorbents. The modified SAP's chemical composition and thermal stability were evaluated using FTIR and TGA methods. Various tests were applied to evaluate the SAP and modified SAP properties, including free absorption properties in water and saline solution, absorption under load, gel‐blocking properties, rheological behavior, and antibacterial properties. The storage modulus indicates that the gel strength and absorbency under load have been enhanced, reaching levels of 57,600 Pa and 24.81 g/g, respectively. It is proposed that the outer layer of the SAP particles has been altered through crosslinking. The surface alteration has also improved thermal stability and prevented unwanted gel blocking.