Abstract
Hydrogels based on saponified products of poly (acrylonitrile, AN)-starch composites were prepared, characterized and their water abosrbency properties examined. The term composite refered to the resultant products of polymerizatin of AN with starch in presence of ceric ammonium nitrate (CAN) as initiator, that is the composite consists of poly(AN)-starch graft copolymer, homopoly(AN) , oxidized starch and unreacted starch. Thus AN monomer was polymerized with gelatinized starch using the ceric ion method. Gelatinization of starch prior to polymerization was affected by heating certain weight of starch in certain volume of distilled water at different temperrature (65, 75 and 85°C). Polymerization was carried out under a variety of coditions. Saponification of poly (AN)-starch composites was performed in sodium hydroxide to yield the hydrogels. The water absorbency properties of these hydrogels were found to rely on variables affecting the magnitudes of both polymerization and saponification. Among these variables mention was made of the starch/liquor ratio, cocentration of ceric ammonium nitrate (CAN), monomer/starch molar ratio, duration of grafting and gelatinization temperature as well as saponification time. Hydrogels display their maximum water absorbency when granular starch was firstly gelatinized at 85°C for 30 min and secondly subjected to polymerization with AN using AN/starch molar ratio of 4.8 and CAN concentration of 10 mmol/L liquor ratio of 12.5 and thirdly sample of the so obtained poly (AN)-starch composite was saponified in sodium hydroxide (0.7 N) at 95°C for 180 min. The saponified product was then precipitated in excess methanol, dried and finally converted into powder. The product (hydrogel) in the powder form exhibited maximum water absorbency of 920 g water per gram hydrogel and 38 mL synthetic urine per gram hydrogel.
Highlights
Hydrogels are three- dimensional hydrophilic polymer network capable of imbibing large amounts of water
The present study was undertaken with a view to enhance the water absorption capacity of maize starch by subjecting the latter to the following consequence of treatments 1) gelatinization of starch at different temperature, 2) polymerization of AN with gelatinized starch using ceric ammonium nitrate (CAN ) as initiator, 3) saponification of poly(AN)-starch composites under the influence of sodium hydroxide and 4) precipitation of the saponified starch composite and its drying and grinding to give the hydrogel in powder form
Controlling the magnitude of each treatment would posses their impact on water absorbency properties of the hydrogel
Summary
Hydrogels are three- dimensional hydrophilic polymer network capable of imbibing large amounts of water. Initiator Concentration: Table 3 shows the effect of CAN concentration on the graft yield%, N% of both composite and graft copolymer and, the impact of this on the water retention value of the hydrogel.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
