EVALUATION OF COPOLYMERS OF POLYETHYLENE OXIDE AND POLYBUTYLENE TEREPHTHALATE (POLYACTIVE) - MECHANICAL-BEHAVIOR

Polyether-polyester segmented block copolymers (Polyactive(R)) on the basis of polybutylene terephthalate (PBT) and polyethylene oxide (PEO) were mechanically tested. Tensile strength and modulus of elasticity in compressive and tensile deformation were recorded according to ASTM standards. These tests were done in vitro under dry a nd wet conditio ns, and after 3, 9 and 25 wk subcutaneous implantation of these mater ials in goats. Strength and modulus of elasticity were higher with inc reased contents of PET in the copolymers. After water uptake, the poly mer displayed a lower strength and stiffness. Disintegration of the ma terials with 70% PEO content and dumb-bell shape was noted at 3 wk. Di sintegration of the cylinders of the same material was seen after 25 w k implantation. Of the materials with 60% PEO content, only four of th e five dumb-bells had disintegrated after 25 wk implantation. The in v ivo test results of all other implants did not show a clinically relev ant decrease of strength and stiffness with time after implantation of the copolymers in the goats. Mechanical behaviour of the various copo lymers seemed mainly determined by the amount and integrity of the PET phase.