Modification of cassava starch by using propionic anhydride and properties of the starch-blended polyester polyurethane

Chemical modification of the cassava starch was conducted through acylation by using propionic anhydride as an esterifying reagent. The reaction was carried out in the presence of a pyridine catalyst and the effects of reaction variables such as the anhydride content, reaction time and reaction temperature on the degree of acylation were investigated. Results from Fourier transform infrared spectroscopy suggested that the hydroxyl groups in the starch molecules were converted into ester groups, accompanied by an increase in water stability of the starch. The propionyl content was found to be non-linearly dependent with the reaction variables. Scanning electron micrographs of the modified starch-blended polyurethane showed a better interfacial adhesion than the normal starch-blended polyurethane. However, results from the soil burial test showed that the modified starch experienced a slower biodegradation than the normal starch.