Quaternary starch based blends: Influence of a fourth component addition to the starch/water/glycerol system

This paper deals with the effects of the addition of a fourth component to the starch glycerol/water/system used in thermoplastic starch materials on the basis of starch sorption site availability. These sites can sorbed both water and glycerol depending on the glycerol content and the chosen relative humidity. Starch sorption sites are saturated by specific glycerol+water concentrations, which defined the starch saturation point. The addition of a fourth component before, near or after this starch saturation point is a potentially interesting concept because of its effect on the mechanical properties of the whole system (quaternary system). This was illustrated with various types of fourth components introduced at low concentrations. The addition of maltose led to an efficient coplasticizing effect only after the saturation point. The addition of a polar polymer led to a strain increase (at break) before and at the saturation point, and to a strain decrease after the saturation point. The addition of fillers at the saturation point led to an unattempted plasticizing effect.