THE INFLUENCE OF BASIC FILLER MATERIALS ON THE DEGRADATION OF AMORPHOUS D-LACTIDE AND L-LACTIDE COPOLYMER

Composite films made of poly L/D copolymer and hydroxylapatite (HA) as filler material were made in two different volume percentages. As ref erences pure copolymer films and composite films with magnesium oxide (MgO) were prepared to serve as strongly basic model filler material. All these materials were immersed in phosphate buffered saline to stud y the effect of filler materials on the degradation rate of the copoly mer. Filled films showed less molecular weight decrease than the unfil led films, while lactate release was higher for the filled films than for the unfilled films. Th is effect implies that the filler mate ria Is influence the degradation mechanism by preventing the occurrence of . the autocatalytic effect of the acidic endgroups, resulting from hyd rolysis of the polymer chains. The polymer chains at the surface of th e material are less protected by the filler materials, which causes a more rapid degradation of these chains and a higher lactate release. A t the same time composites seem to show an erosion type of degradation rather than bulk degradation in unfilled materials.