Effects of moisture and degradation time over the mechanical dynamical performance of starch-based biomaterials

The viscoelastic behavior of a polymeric system composed from a blend of starch and a copolymer of poly(ethylene-vinyl alcohol)-(SEVA-C)- was studied by dynamic mechanical analysis. Two main relaxation processes, at about 30 and 90°C, were identified, and their kinetic behavior was studied. The studied materials are being considered for a range of orthopedic applications, which demands the characterization of the dependence of its solid rheological properties upon moisture content. Additionally, it is of main importance to study the evolution of its dynamic mechanical properties as a function of immersion time in simulated physiological solutions. A plasticization effect due to moisture was clearly observed on the low-temperature relaxation. The degradation of SEVA-C in 0.154 M NaCl and 0.154 M NaCl+10% v/v bovine serum solutions provided indication that no significant decreasing of stiffness is observed for times up to 60 days. The effects of an enzymatic environment were evident, the degradation processes being much faster in the later solution.