Effects Of Stress And Biological Environment On Polymeric Implants' Durability

摘要

The results of investigations of durability of bioinert polysulfone(PSU)and its composites,containing either 15 % of short carbon fibers randomly oriented(PSU + CF MD)or 40 % of long fibers uniaxially oriented(PSU + CF ID),were presented.The effects of a presence,orientation,length and volume part of carbon fibers on mechanical properties of the composites were determined(Table 2).The materials were subjected to creep testing in dry or in vitro(in Ringer fluid)conditions under variable stress(10-400 MPa)or without it(incubation).Then the changes of their mechanical properties were investigated(Table 3)and the observations of surface fractures by SEM method(Fig.2)as well as measurements of interlayer shear strength(ILSS - Table 4)were done.The changes of the structures were determined on the basis of glass transition temperature(T_g)by means of DSC method.The long-term strength(sigma_d- Table 6 and Fig.5)and the values of permissible(maximum)load(sigma_maks- Table 7 and Fig.6)for the materials investigated,in relation to the assumed time of bone tissue fixation,were determined on the basis of creep tests at in vitro conditions.It has been found that PSU and its composites can work safely under long-term load in biological environment at the level of 30-40 % of initial strength during the period required for bone fixation.Introduction of carbon fibers to the polymer allow to subject the material to considerable loads but accelerates the process of its degradation in body fluids' environment.