Synthesis and swelling properties of microcrystal muscovite composite superabsorbent

A new microcrystal muscovite composite superabsorbent (MMCSA) was synthesized by redox copolymerization of acrylic acid (AA), acrylamide (AM) and itaconic acid (IA) with ammonium persulfate (APS) and sodium bisulfite used as redox initiator, N, N-methylene bisacrylamide (MBA) used as crosslinker and microcrystal muscovite used as an inorganic additive. Factors affecting the water absorption and gel strength of the microcrystal muscovite composite superabsorbent, such as crosslinker amount, microcrystal muscovite amount, neutralization degree of AA and IA, IA/AA mass ratio and (AA + IA)/AM mass ratio were systematically studied. Morphology, structure and thermostability of microcrystal muscovite composite superabsorbent were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimertic analysis (TGA), respectively. The results show that swelling kinetics of microcrystal muscovite composite superabsorbent can be expressed by the Voigt-based viscoelastic model. Water absorption of microcrystal muscovite composite superabsorbent is rapid, requiring 24.55 min to reach 63% of equilibrium absorbency (1218 g/g). Water absorbency, gel strength and thermostability of microcrystal muscovite composite superabsorbent increase with microcrystal muscovite amount increasing from 5% to 15%. Microcrystal muscovite is physically combined into the polymeric network without destroying its polycrystalline structure and the surface of the microcrystal muscovite composite superabsorbent has some deep and small macropores.