International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 02 Issue: 02 | May-2015 w.irjet.net p-ISSN: 2395-0072 © 2015, IRJET.NET- All Rights Reserved Page 442 Modification of Sorghum Starch for Production of Superabsorbents M. D. Teli 1 , A. Mallick 2 1 Professor of Fibres and Textile Processing, Dept. of Fibres and Textile Processing Technology, Institute of Chemical Technology, Maharashtra, India 2 Ph.D. Tech. Research Scholar, Dept. of Fibres and Textile Processing Technology, Institute of Chemical Technology, Maharashtra, India Abstract - Starch extracted from Sorghum bicolor grains was gelatinized and grafted with acrylic acid (AA) and acrylamide (AAm) using potassium persulphate(KPS) as an initiator. Different parameters of grafting reaction such as reaction time, temperature, initiator concentration, and starch to monomers ratio were optimized. Material thus produced was dried, grounded and characterized using FT-IR and SEM. Grafted starch products were saponified with 0.1 N NaOH solution followed by neutralization and drying. Maximum absorbency of 225.5 gg -1 in normal water was obtained, qualifying it as super absorbent product (SAP). Keywords: Grafting, Starch, Superabsorbent 1. INTRODUCTION Superabsorbent polymers are hydrophilic polymers which are able to absorb and retain a fairly large amount of water within their structure. This becomes possible as the polymers, which are hydrophilic in nature, do not get dissolved in water and hold the water molecules within their swollen three dimensional interconnected structures (hydrogels). There is no definite lower limit of absorbency to call a hydrogel as a superabsorbent, and many authors have referred their hydrogels with high absorbency as superabsorbent when the water retention capacity of the polymer was more than 100 times of its own dry weight (or more than 1000%)[1]. These hydrogels attracted wide interest due to their intriguing properties such as high absorption and swelling capacity, slow release of moisture, etc. Some of these products are widely used in personal care, agriculture and biomedical applications [2]. Although synthetic superabsorbent polymers show very high water retention properties and fair to good gel strength, the biodegradability of these acrylate based SAPs is very poor causing increase in environmental load [3]. Therefore, incorporation of biopolymers for synthesis of SAP became preferred option to the use of their synthetic counterparts. Products made of natural biopolymers are biodegradable and more importantly, their sources are cheap, renewable and sustainable. Natural biopolymers such as cellulose, starch, etc. are effective alternative of synthetic superabsorbent polymers [4,5]. Starch is basically composed of two fractions, amylopectin and amylose and both constitute 97-98% of dry weight of starch. These are polysachharides and their ratio varies with the botanical origin of the starch. Great Millet or Sorghum (Sorghum bicolor L.Moench) is a cheap and alternative source of starch. Sorghum, commonly known as jowar in )ndia is the world’s fourth major cereal in terms of production, and fifth in acreage following wheat, rice, maize and barley, and serves as a staple food crop in India [6. Sorghum grain contains starch ranging from 68-75% depending upon variation in seed quality, region and climatic conditions [7]. Grafting of starch has been widely reported by different researchers. Different polymerization techniques viz. solution polymerization, emulsion polymerization, suspension polymerization, polymerization via irradiation, etc. are used for producing superabsorbent hydrogels. Different initiation systems such as ceric ammonium nitrate, potassium persulphate etc. also have been used for these processes [8,9]. Chen et al. (2004) utilized batata starch for grafting with acrylic acid and acrylamide under gamma radiation with polyethylene glycol as crosslinker [10]. Cassava starch has been grafted by acrylamide using ceric ammonium nitrate by Jyothi et al. (2012) [3]. Peng et al (2007) on other hand used acrylamide (AAm), diallydimethylammonium chloride (DMDAAC) and sodium starch sulfate for producing SAP using ammonium persulpfate as grafting initiator [2]. The present paper deals with extraction of starch from sorghum and its modification as a superabsorbent by grafting hydrophilic monomers onto it. It discusses the optimization of the process as well as the characterization of the modified starch and the product developed as a superabsorbent.