Preparation and Water Absorbency of a Novel Poly(acrylate-co-acrylamide)/Vermiculite Superabsorbent Composite Qunwei Tang, Jianming Lin, Jihuai Wu, Yuwen Xu, Chuanjuan Zhang Institute of Material Physical Chemistry, Huaqiao University, Quanzhou 362021, China Received 21 April 2006; accepted 18 July 2006 DOI 10.1002/app.25531 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: A novel poly(acrylate-co-acrylamide)/expanded vermiculite (EVMT) superabsorbent composite was synthe- sized by aqueous solution polymerization method. The water absorbency of the superabsorbent composite still reaches 850 g/g when 50 wt % EVMT is added, which is significant in decreasing the production cost of the superabsorbent com- posites. By controlling the molar ratio of acrylic acid mono- mer and acrylamide monomer, and neutralization degree of acrylic acid, the hydrophilic groups on the composite can be adjusted, and it is found that the collaborative absorbent effect of CONH 2 , COOK, and COOH groups is supe- rior to that of single CONH 2 , COOK, or COOH group. Ó 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 735–739, 2007 Key words: superabsorbent composite; poly(acrylate-co-ac- rylamide); expanded vermiculite; water absorbency INTRODUCTION Superabsorbent polymers have a network structure with a suitable degree of crosslinking. 1,2 Not only are they able to absorb hundreds to thousands times their own mass of water, but also the absorbed water is hardly removed under some pressure. Because of their excellent characteristics, superabsorbents have raised considerable interest and researches, and have been used in health, agriculture, and horticulture 3–7 since the first superabsorbent polymer was reported by the US Department of Agriculture in 1969. 8 Polyacrylamide and polyacrylate polymers are two kinds of the superabsorbents with higher water absorbency, but the polymers’ higher production cost and lower gel strength restrict their application widely. Expanded vermiculite (EVMT) is a layered aluminum silicate with exchangeable cations and re- active OH groups on the surface. It is expected that the type and amount of hydrophilic groups, as well as the network structure of the superabsorbent com- posites, are improved by copolymerizing with acryl- amide monomer, acrylate monomer, and EVMT micro- powder. Consequently, comprehensive absorbent prop- erties of superabsorbents are enhanced and the production cost of superabsorbents is reduced. 1,2,7 In this work, a novel poly(acrylate-co-acrylamide)/ver- miculite superabsorbent composite was synthesized by aqueous solution polymerization method. The influence of vermiculite amount, monomer am- ount, crosslinker, initiator, neutralization degree, and reaction temperature on the absorption properties is discussed. EXPERIMENTAL Preparation of poly(acrylate-co-acrylamide)/ vermiculite superabsorbent composite Acrylic acid monomer (36.0 g), distilled under reduced pressure prior to use, was neutralized at room tem- perature with an aqueous solution containing 21.0 g potassium hydroxide to achieve the desired neutrali- zation degrees (75%) of the sample. Acrylamide monomer (9.0 g) and expanded vermiculite (EVMT; 22.5 g) micropowder with an average particle size smaller than 2  10 5 m and specific surface area larger than 20 m 2 g 1 were dispersed in the neutral- ized monomers solution mentioned earlier. Cross- linker N, N 0 -(dimethylene) acrylamide (0.036 g) was purified by recrystallization from 66 wt % ethanol/ water solution, and dissolved in the monomer/ EVMT mixture. The mixed solution was then de- gassed under vacuum ( 300 Pa) for about 30 min. Radical initiator potassium persulfate (0.54 g) was added to the solution consisting of monomer, EVMT, and crosslinker. Correspondence to: J. Wu (jhwu@hqu.edu.cn). Contract grant sponsor: The National Natural Science Foundation of China; contract grant number: 50572030 and 50372022. Contract grant sponsor: The Key Scientific Technology Program of Fujian, China; contract grant number: 2005HZ01-4 and 2004HZ01-3. Journal of Applied Polymer Science, Vol. 104, 735–739 (2007) V V C 2007 Wiley Periodicals, Inc.