Effect of filler type on the mechanical properties of self-reinforced polylactide-calcium phosphate composites

Bioabsorbable polymers are of interest as internal fracture fixation device s. Self-reinforcement has been developed to improve the mechanical properti es of the material and the addition of calcium phosphate fillers improves t he bioactivity. Composite plates, produced by compression molding preimpreg nated sheets of polylactide fibers coated in a polylactide matrix have been degraded in simulated body fluid for up to 12 weeks. Some samples also con tained hydroxyapatite or tricalcium phosphate filler particles. Degradation was measured by monitoring the water uptake and mass decrease of the sampl es, as well as carrying out four point bend tests to assess the mechanical properties of the material. By 12 weeks, it was found that the unfilled sam ples absorbed more water and showed greater mass loss than the samples cont aining calcium phosphate fillers. Also, the flexural modulus and yield stre ss decreased significantly at week 12 for the unfilled samples. Adding hydr oxyapatite (HA) or tricalcium phosphate (TCP) to the composite increased th e flexural modulus and yield strength to values within the range of those r eported for cortical bone and these values were maintained over the 12-week period. (C) 2001 Kluwer Academic Publishers.