Effect of mica on water absorption of acrylamide-itaconic acid superabsorbent nanocomposites

Abstract

The superabsorbent polymer and its nanocomposite of acrylamide (AM)/itaconic acid (IA) were synthesized by solution polymerization in the aqueous solution of AM with IA as a comonomer and mica used as an inorganic additive in the polymerization process. This reaction was initiated by an initiator couple of ammonium persulfate and N N, N′, N′- tetramethylethylenediamine (TEMED). The N, N′-methylenebisacrylamide crosslinker was used in the polymerization. The influences of the concentrations of IA, crosslinker, mica content, and reaction temperature on the water absorption of the superabsorbent polymer systems were examined. In addition, the effects of the mica content on water absorbency under load of the synthesized copolymers and composites at 0.28 and 0.70 psi were examined. The water absorbency of the synthesized copolymers in artificial urine was also investigated. The functional groups of synthesized copolymers and composites were investigated by Fourier Transform Infrared Spectroscopy, and thermal properties were characterized by thermal gravimetric analysis. The structure and surface morphology were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Moreover, the viscoelastic properties of the swollen gel were investigated. The results showed that the polymer chains intercalated into the silicate layer in the mica and created more network junctions in the polymer structure. The synthesized copolymer gives the highest water absorbency of 640+7 times its dry weight at the AM-to-IA ratio of 95:5 and 5% mica, and can absorb up to 79+3 times its dry weight in artificial urine. The mica addition results in higher water absorption of 748+5 and 76+2 times its dry weight in artificial urine with increased gel strength and enhanced thermal stability of the synthesized superabsorbent nanocomposites. Such composites were obtained from the polymerization condition of AM/IA 95/5, 5% wt of mica, 0.2% mole of N-MBA, 0.3% mole of APS, 1.2% mole of TEMED (0.2 ml) and a reaction temperature of 50°C. This superabsorbent nanocomposite has intercalation layers in mica with increasing gel strength, higher water absorption and thermal stability.