Effect of blending tricalcium phosphate on hydrolytic degradation of a block polyester containing poly(L-lactic acid) segment

The effect of blending tricalcium phosphate (TCP) on hydrolytic degradation of a new type of poly(L-lactic acid)/poly(ethylene;hexamethylene / sebacate) block polyester (60:40 wt%) was studied. 100- and 250-mu m film specimens blended with 0, 10, and 30 wt% TCP were immersed in phosphate buffered saline (pH 7.4) at 37 degrees C for up to 80-104 weeks. At appropriate intervals, water absorption, dry and wet tensile strength, molecular weight, and thermal properties of the specimens were measured by weighing, tensile strength testing, size exclusion chromatography, and differential scanning calorimetry, respectively. Some samples were characterized by H-1 NMR spectroscopy. Blending of TCP with the block polyester was effective in retarding degradation. The blended TCP was thought to retard degradation for the most part by neutralizing the lactic acid oligomers produced by hydrolysis of the poly(lactic acid) part during the initial stage of degradation.