Effects of environmental exposure on carbon polysulphone composites

In vivo and in vitro studies were designed to characterize the material degradation associated with implantation of carbon fibre-reinforced polysulphone (C/PS). Composite plates were compression moulded for both studies, and a fibre orientation of 0 degrees with the long axis and a fibre volume fraction of approximately 55% were used. The in vitro experiment involved soaking three groups of four plates each at 4, 12 and 26 wk in 0.9% saline solution at 37 degrees C. The plates were measured for weight gain after each time period and mechanically tested non-destructively in four-point bending to determine modulus. The in vivo experiment involved implanting three groups of eight composite plates (24 total) subcutaneously in the abdomens of 12 rabbits (two implants/animal). Implants were harvested at 4, 12 and 26 wk after implantation and evaluated for changes in weight or modulus of elasticity. In vitro results showed a statistically significant (P less than 0.05 paired t-test) increase in weight for all time periods: 0.41, 1.25 and 0.93% weight gain for the 4, 12 and 26 wk periods respectively. In vivo results were similar to those in vitro: 0.66, 1.06 and 1.15% weight gain for the 4, 12 and 26 wk periods respectively (P less than 0.05 paired t-test). There was no statistically significant difference between the pre- and post-implantation modulus of elasticity for any time period in vivo or in vitro. However, in both studies, on average, the modulus tended to increase with environmental exposure.