Preparation of a kaolinite-poly(acrylic acid acrylamide) water superabsorbent by photopolymerization

A novel kaolinite-poly(acrylic acid acrylamide) water superabsorbent with a water absorbency and salt solution absorbency of 433 and 108 g/g, respectively, was successfully synthesized by the photopolymerization of acrylic acid with acrylamide in the presence of kaolinite powder under 30 min of ultraviolet irradiation at room temperature. The results showed a synergetic effect of the mixed photoinitiators (Michler's ketone and benzophenone) on the water absorbency, and the incorporation of less than 10 wt % kaolinite into the water superabsorbent slightly improved the water absorbency and salt solution absorbency and obviously upgraded the water retention, as demonstrated by retention testing as well as thermogravimetric analysis and differential scanning calorimetry. Fourier transform infrared spectroscopy verified the structure of the kaolinite composite superabsorbent. (c) 2006 Wiley Periodicals, Inc.