Synthesis and characterization of native and modified bitter yam starch grafted with acrylonitrile

Abstract

This analysis studied the effects modification on the properties of starch-based polymer grafted with acrylonitrile (copolymers). Starch was extracted from bitter yam. The starch was modified by heating the solution above 70 °C and then esterified with phthalic anhydride to produce a pregelatinized phthalated derivative. Acrylonitrile was grafted onto natural and pregelatinized phthalated starch at 120 °C using calcium oxide from snail shell as the initiator. The grafting reaction of starch with poly(acrylonitrile) and the phthalation of the starch were both confirmed by Fourier transform infrared (FTIR). Scanning electron microscopy analysis revealed changes in the morphology of the pregelatinized phthalated grafted copolymers. The X-ray diffractogram showed that native starch grafted copolymer displayed broad diffraction peaks (amorphous), but the phthalated bitter yam starch grafted with acrylonitrile had prominent diffraction peaks (crystalline). Thermogravimetry analysis revealed that the phthalated grafted copolymer has better thermal stability than the native grafted copolymer.