Preparation Of Poly Acrylic Acid System/Nonmetal Minerals Superabsorbent Composite By UV Photoinitiation

In this paper, poly (acrylic acid-acrylamide) /nonmetal minerals superabsorbent composite is synthesized by UV photopolymerization. Kaoline and bentonite are layered aluminium silicate with exchangeable cations and reactive -OH groups on the surface. So it is expected that the type and amount of hydrophilic groups as well as the network structure of the superabsorbent composite are improved by polymerization between acrylic acid, acrylamide and kaoline/bentonite. Consequently, the comprehensive absorbent properties of superabsorbent are enhanced and the production cost of sunerabsorbent is reduced.The factors influencing on water absorbency for the superabsorbent composite such as photoinitiator, crosslinker, the degree of neutralization, the AA/AM molar ratio and the time of exposure are investigated in this paper. The suitable preparing conditions of the composite has been set down by a series of experiments, and the structure- property relation has been discussed. The superabsorbent composite is characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetry analysis (TGA).Under appropriate conditions, when the kaolinite accounts was 15 %, the water absorbency and salt water absorbency of the composite are 1095 g/g and 94.7 g/g, respectively. The absorbed water is over 70% within ten minutes, and the absorbed water is 39.9% after being dried 12 hours at 60℃, which indicates the composite has better water absorbency, faster absorption velocity and stronger water retaining. Under the similar conditions, when the bentonite accounts was 10 %, the water absorbency and salt water absorbency of the superabsorbent composite are 1135 g/g and 100.1 g/g, respectively. The absorbed water is over 70% within ten minutes, and the absorbed water is 50.24% after being dried 12 hours at 60℃. Compared with absorbent resin without clay, the water absorbency and salt water absorbency of the composite increase 14.88% and 23.28%, respectively, and the water retaining improves 44.45%, which indicates that adding in proper bentonite can enhance absorption property, water absorbency and water retaining performance.The results of FTIR, XRD and SEM are coincident, which indicate that the graft polymerization take place between -OH groups on clay surface with organic monomers and crystal structure of clay doesn't change and the polymer don't intercalated the layers of clay. Therefore, clay can be dispersed uniformally in the polymer matrix.