Influence of Carboxylic Acids on Mechanical Properties of Thermoplastic Starch by Spray Drying

Abstract

The influence of carboxylic acids on the mechanical properties of TPS produced by spray drying have been investigated. Both malic acid and citric acid (polycarboxylic acids) were used as plasticizer. Starch was spray-dried from solution to prepare amorphous TPS dog bones by compression molding. X-ray Diffraction (XRD) results showed that all the freshly solution spray dried TPS powder and dog-bones samples were amorphous irrespective of the amount of plasticizer added. Scanning Electron Microscope (SEM) was used to examine the morphology of solution spray dried TPS powder. No noticeable difference was observed on the morphology between the samples. Particles were spherical and homogenous surface was observed. The FT-IR analysis indicated the interaction of plasticizers with starch chains by hydrogen bonding. In TGA analysis, apart from moisture loss at 100oC, samples were thermally stable up to 170oC temperature. Tensile testing showed that Malic Acid plasticized samples exhibited a more elastic behavior as compared to Citric Acid plasticized samples. Whereas, the quantity of the plasticizers and tensile strength of TPS dog-bones was inversely proportional to each other.