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 st arch 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 degreesC, were identified, and their kinetic behavior was studied. T he studied materials are being considered for a range of orthopedic applica tions, which demands the characterization of the dependence of its solid rh eological properties upon moisture content. Additionally, it is of main imp ortance to study the evolution of its dynamic mechanical properties as a fu nction of immersion time in simulated physiological solutions. A plasticiza tion effect due to moisture was clearly observed on the low-temperature rel axation. 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 enzymat ic environment were evident, the degradation processes being much faster in the later solution. (C) 2000 John Wiley & Sons, Inc.