NOVEL HIGH-PERFORMANCE MATERIALS FROM STARCH - 3 - INFLUENCE OF DEGREE OF SUBSTITUTION AND AMYLOSE AMYLOPECTIN RATIO ON PERFORMANCE/

The improvements in mechanical properties obtained by orienting starch -ether films were further examined, specifically with regard to their dependence on degree of substitution of the starch and on its amylose/ amylopectin ratio. It was found that the degree of substitution had li ttle or no influence on the mechanical properties of these materials a t comparable deformations during drying. On the other hand, there were clear dependences of the tensile strength and toughness on the amylos e/amylopectin ratio. In particular, the larger this ratio, the stronge r and tougher the materials were after orientation. In overall perform ance, the oriented starch-ether films can be described as tough plasti cs, with tensile strengths between 15 and 47 MPa, tensile moduli betwe en 320 and 670 MPa, and elongations at break between 5 and 120%. These values are comparable to those of medium-density or even high-density polyethylene.