Influence of Starch and Glycerol on the Properties of Chitosan by Positron Annihilation Spectroscopy

Abstract

Two types of chitosan (CS), a and b, were blended with different concentrations of starch and cast to obtain films. The addition of 1% glycerol was used as a plasticizer to increase film flexibility. The properties of the obtained films were studied by positron annihilation lifetime spectroscopy, X-ray diffraction, and scanning electron microscopy. The results indicate that pure b-CS had smaller size free-volume holes with high fractions than pure a-CS; this was attributed to the difference in bonding of main chains in b-CS. The addition of starch (>20% up to 50%) reduced the size of the free-volume holes and increased their fraction because of the close packing of chain segments. The effect of 1% glycerol to the CS starch blends indicated that some modification took place