Optimization of synthesis and characterization of cassava starch‐graft‐poly(acrylonitrile) using response surface methodology

Abstract

Graft copolymerization of poly(acrylonitrile) onto cassava starch was carried out with potassium persulphate (PPS) as the free radical initiator using a response surface Box-Behnken design. Different levels of monomer concentration, initiator concentration, and temperature were used, and regression models were generated in terms of these factors, which can be used to predict the grafting level and efficiency at a given level of the factors. The grafted starches were characterized by FTIR, XRD, and SEM analyses and determination of %grafting (%G), N-content, thermal properties, water and saline solution retention, and rheological properties. Under the conditions used, %G was found to depend only on the temperature used for the reaction. The maximum %G of 120.1 was obtained for the sample synthesized under the following conditions: weight of AN ¼ 0.753 mol/10 g starch, weight of PPS ¼ 0.284 g and temperature ¼ 55 C, and the grafting efficiency was 30.03%. The absorption bands at 2243 cm À1 for the nitrile group (ACN) in the FTIR spectra of the products confirmed the grafting reaction. There was a decrease in crystallinity and disappearance of the granular structure after grafting of the starch. The melting temperatures of the graft copolymers determined by differential scanning calorimetry analysis were higher than that of the native starch. The grafted starches exhibited very high thermal stability as observed from the thermogravimetric analysis. The superabsorbent polymer prepared from the grafted starch by alkali saponification exhibited a maximum water absorbency of 636 g/g. V C 2011Wiley Periodicals, Inc. J Appl Polym Sci 122: [1546][1547][1548][1549][1550][1551][1552][1553][1554][1555] 2011

Cassava starch‐graft‐poly(acrylonitrile)‐coated urea fertilizer with sustained release and water retention properties

“…The XRD patterns of representative samples, S4 and S9, are shown in Figure . This result was consistent with earlier reports by Jyothi et al . Aged thermoplastic maize starch–zein blends were reported to produce similar types of XRD patterns due to the crystallization of the short outer chains of amylopectin .…”

“…The concentration of acrylonitrile used for the synthesis of the graft copolymer was found to have a significant positive effect on nitrogen content. Similar result was reported earlier also …”

“…The pregelatinization of starch and the subsequent grafting reaction might be responsible for the observed differences in the morphological structure. Similar observations of loss of uniformity and planarity were reported earlier with cassava starch‐graft‐poly(AN) as well as cassava and potato starches grafted with acrylamide and polyethylene . The change in morphological structure confirmed the grafting reaction of starch.…”

“…The scanning electron micrograph of the native cassava starch showed its granular nature (Figure a). The starch granules appeared spherical with a flat surface on one side containing one or more pits, which is the typical granular morphology of cassava starch . However, starch‐g‐poly(AN) showed no granular appearance (Figure b and c).…”

Synthesis and Characterization of Starch Vernolates in Organic Solvents

“…The Tm of native cassava starch in this study having about 10-13% moisture was 139°C as shown in Figure 1 below. It has been reported elsewhere that the Tm of cassava starch with 8-10% moisture content was found to be 162°C [28,29]. Reports from separate study indicated that the glass transition temperature of native cassava starch which was 139°C has decreased during solution state enzymatic esterification with recovered coconut oil [18].…”