A series of sodium humate/polyacrylamide/clay (SH-PAM-Clay) hydrogels was synthesized by solution polymerization and crosslinked using acrylamide

sodium humate(SH) and clay Laponite RD as raw materials

potassium persulfate (KPS) as the initiator and N

N′-methylenebisacrylamide (MBA) as the cross-linking agent.The morphology of the hydrogels was characterized by field emission scanning electron microscope (FESEM)

and their rheological and water-absorption properties were also examined.Experiments showed that SH/PAM/Clay hydrogels have homogeneous network structures and high water-absorbent properties.Swelling experiments show that the swelling rate decreases with the increase of SH content

and the introduction the hydrophilic clay improves the water absorbency properties of SH/PAM/clay hydrogel systems.Relaxation of polymer chains of the hydrogels controls the swelling process.Rheological experiments show that the elastic response of the hydrogel system is stronger than the viscous response.Chemical cross-link due to chemical cross-linker and physical cross-link due to weak interactions coexist in the hydrogel network.The interactions between SH and polymer chains are very weak

and SH acts as lubricant.While the contents of clay in the hydrogels play an important role in affecting rheological properties of the hydrogel system.The Han plot proves that clay and SH are compatible with PAM

and SH/PAM/clay hydrogels are homogeneous.