Effect of cross-linker and initiator concentration on the swelling behaviour and network parameters of superabsorbent hydrogels based on acrylamide and acrylic acid

Abstract

Poly (acrylamide-co-acrylic acid) [poly (AAm-co-AAc)]-based hydrogels were prepared by varying the cross-linking agent concentration (NMBA) in the range of 0.0077% to 0.077%. The effect of the NMBA content on swelling parameters, such as water absorbency, swelling ratio on the hydrogel was studied by keeping two monomers content, that is, AAm and AAc constant. The effect of KPS as an initiator in the range of 0.1% to 0.5% on the water absorbency of the hydrogels was also studied. The swelling value could be modulated in a great range by varying the cross-linking agent (NMBA) or initiator (KPS) concentration at fi xed monomer concentration. The synthesized hydrogels were characterized by FTIR, SEM and network parameters, such as average molecular weight between cross-links (Mc), cross-link density (q) and mesh size (ξ). The experimental results showed that the equilibrium water absorbency decreases from 707.23 to 389 with increasing the NMBA content from 0.0096 % to 0.0385%. The network parameters, such as average molecular weight between cross-links (Mc) were decreased from 2.33 x 10 12 to 2.30 x 10 11 and cross-link density (q) decreased from 3.07 x 10 -11 to3.09 x 10 -11 ; although mesh size (ξ) increased from 3.00 x 10 6 to 8.89 x 10 6 with increase in percentage of NMBA content from 0.009265% to 0.077%. The equilibrium water absorbency of various hydrogels were studied in distilled water and different types of saline solutions, which exhibited that hydrogels have higher equilibrium water absorbency in 0.009% saline (NaCl) solution than in 0.09% and 0.9% saline solutions. From the results it was clear that water absorbency increased from 302 to 573 g water/g sample with increasing the KPS content from 0.1 to 0.5%.

Stomata‐Inspired Membrane Produced Through Photopolymerization Patterning

“…Then the concentration of the crosslinker in the frame becomes higher than that of the base. The slightly cross‐linked polymer in the base represents a higher degree of swelling ratio, compared to the highly cross‐linked polymer in the frame . These results imply that polymer density in the base is smaller than that in the frame .…”

Preparation of a biodegradable superabsorbent polymer and measurements of changes in absorption properties depending on the type of surface‐crosslinker

“…We think that, as EGDGE has longer chains than EC, glycerol, and BD, the SSAP with EGDGE has the largest surface pore size. The size of the network is determined by the crosslinking density and molecular weight (chain length) between two crosslinking points . In other words, the crosslinking density of the SAP using EGDGE having a longer chain than BD, glycerol and EC is the lowest.…”

Fuzzy Optimization on the Synthesis of Chitosan-Graft-Polyacrylic Acid with Montmorillonite as Filler Material: A Case Study

“…In terms of the pore distribution, a higher initiator content provides additional free volume that allows higher water mobility leading to a higher swelling degree [52]. Furthermore, an increase in the initiator concentration is able to promote the formation of polymer chain ends in the network leading to higher swelling activities [54].…”