Abstract: The addition reaction of a lactic acid-based diol intermediate(LPEG), hydroxyapatite with toluene-2,4-diisocyanate(TDI) was employed to form the covalent hybrid of hydroxyapatite and lactic acid-based polyurethane. The structure and thermal stability of the hybrid were analyzed and compared with the corresponding blends. Thermogravimetric analysis shows that the remained fractions of HA-g-LPEU5K and HA/LPEU5K are 92.5% and 41.7%, respectively. The hydrids are still homogeneous while precipitation is found in the blend solutions after settling at temperature for three days. The stability of the hybrid is significantly higher than that of the blends, which confirms that the covalent hybrid of lactic acidbased polyurethane and hydroxyapatite is successfully obtained. In addition, the hybrid systems exhibit degradable properties.

Key words: Lactic acid-based polyurethane, hydroxyapatite, covalent hybrid