PROCESSING AND IN-VITRO DEGRADATION OF STARCH EVOH THERMOPLASTIC BLENDS/

This paper describes the processing dependence of the mechanical prope rties of three blends of starch/ethylene vinyl alcohol (EVOH) with pot ential uses as biomaterials. These blends exhibit a distinct rheologic al behaviour and mechanical performance. Using shear controlled orient ation in injection moulding (Scorim) it was possible to induce anisotr opy into the mouldings and to simultaneously enhance stiffness and duc tility. Degradation was studied in simulated physiological solutions ( Hank's balanced salt solution) with and without added bovine serum. Bo th the dry weight loss and the changes in mechanical properties were d etermined for ageing periods up to 80 days. The degradation behaviour proved to be strongly dependent on the formulation of the material stu died, and on the addition of proteins. The susceptibility of the starc h/EVOH blends to degradation when sterilised with ethylene oxide (EtO) was also studied, and showed that the polymers could stand one EtO st erilisation cycle. However, two consecutive cycles severely degraded t he polymer structure and properties.