Study on superabsorbent composite, 14 Preparation of poly(acrylic acid)/organo-attapulgite composite hydrogels and swelling behaviors in aqueous electrolyte solution

Otgano-attapulgite (organo-APT) was prepared by modifying APT using four quaternary ammonium salts with various lengths of the alkyl group, including (octyl)trimethylammonium bromide (OTMABr) and (stearyl) trimethylammonium chloride (STMACl), etc. A series of composite hydrogels, poly(acrylic acid)/organo-APT, from acrylic acid (AA), and orgoano-APT was prepared by aqueous polymerization, using N, N'-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The organification and organification degree of APT as well as the corresponding composites were characterized by FTIR. TGA, and XRD. The effects of the length of the alkyl group for different quaternary ammonium salts, organification degree of APT, and organo-APT content on water absorbency and swelling behaviors in various electrolyte solutions were investigated in this study. Equilibrium water absorbency strongly depends on chain length of the alkyl group of quaternary ammonium salts, organification degree of APT as well as organo-APT content. Longer alkyl group, higher organification degree, and proper organo-APT content are of benefit for the improvement of equilibrium water absorbency. Equilibrium water absorbency in distilled water for PAA/APT was enhanced from 350.1 to 562.1 g(.)g(-1) after 10 wt.-% organo-APT, modified with STMACl for the highest degree, was introduced. The kind of cation is the key factor influencing equilibrium water absorbency of these composite hydrogels in electrolyte solutions. Organification of APT could enhance responsiveness of the corresponding composite hydrogel to electrolyte solutions.