THERMOPLASTIC STARCH FILMS. INFLUENCE OF INCORPORATION OF HYDROXYPROPYL-METHYL-CELLULOSE AND CITRIC ACID

Abstract

The aim of this work was to analyze the influence of citric acid (CA) and hydroxypropyl-methyl-cellulose (HPMC) addition in thermoplastic starch films obtained by compression-molding. Two ratios of HPMC- starch (10% and 20%) were considered while starch: CA ratio was of 1: 0,01. The films were characterized as to micro- and nano-structure using Scanning Electron Microscopy (SEM) and X-ray diffraction. Further, the water solubility, CA linked, mechanical and thermal properties were characterized. The starch-HPMC films showed phase separation although the glass transition analysis showed partial miscibility of the starch and HPMC which is accentuated with the addition of CA. The incorporation of HPMC and CA promoted the decrease of water vapor permeability and a slight increase in the oxygen permeability. The CA addition resulted in an increase of the elasticity modulus and decrease in the extensibility of films, which agrees with the cross-linking effect. The optical properties show a decrease in the material compactness with the CA presence causing higher film transparency

Keywords

• Compression molding
• Crosslinking
• Micro-Nano-structure
• Partial miscibility.