Synthesis and industrial applications of superabsorbent polymers

Abstract

Superabsorbent polymers (SAPs) are cross-linked networks of a hydrophilic polymer, with a high capacity for water uptake. In this thesis, homopolymer and copolymer based SAPs were prepared with varying the content of cross-linker. sodium polyacrylate (NaPA) was prepared by free radical bulk polymerization technique. N,N'-methylenebisacrylamide (MBA) and potassium persulfate were used as cross-linking agent and as initiator, respectively. Moreover, novel superabsorbent copolymers were prepared by copolymerization of sodium acrylate (NaA) and different synthetic monomers [(glycidyl methacrylate (GMA), maleic anhydride (MA) and methyl methacrylate (MMA)]. These copolymers in various compositions were synthesized by free radical bulk polymerization using different content of cross-linker MBA. Amount of cross-linker and synthetic monomers were varied to obtain the optimum value to produce maximum water absorbency. In another section of this thesis, characterization and evaluation of the SAPs were performed using analytical techniques- such as differential scanning calorimeter (DSC), thermal gravimetric

analysis(TGA), fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The gel fraction of the synthesized SAPs was evaluated. The influence of variables such as cross-linker content and feed compositions on the water absorbance and viscosity of the prepared polymers were also examined. Experimental results show that absorption characteristics and gel fraction of sodium polyacrylate (NaPA) were dependant on the content of cross-linker in the system. Superabsorbent polymer [sodium polyacrylate (NaPA)] is used to improve the absorbance behavior and performance of the natural rubber to produce, roofing sheets used in hot weather. The morphology of the obtained rubber compound was investigated in details throughout this thesis. Furthermore, the potential practical applications of SAPs [poly(sodium acrylate-co-methylmethacrylate)] was investigated as a new concrete additive. The influence of SAPs on compressive strength by varying the percentage of copolymers by weight of cement were studied. The results revealed that the synthesized SAPs having high absorbance capacity were successfully obtained in this study.