The Properties Of HA-P (CL-LA) Composites

Hydroxyapatite can be obtained by calcining bone of animal teeth. Ring-opening polymerization ofε-caprolactone will be induced on the OH of hydroxyapatite to prepare HA-PCL composite biological material. FTIR, TEM, PLM, DSC and SEM is used to analyze and characterize the structure of the material. Also, its mechanical properties are tested. The results show that:HA affects crystallization of PCL,the crystallinity of PCL was reduced from 60% to 43.67%, and the crystal of PCL is small grain. The maximum tensile strength of HA-PCL composite biomaterials can reach 19.96MPa and the elongation could reach 126%.This indicates that the HA can improve the toughness of PCL. There is obviously appearance of wire drawing in the SEM. For good mechanical properties of the composite HA-PCL biological material which is synthesized by this method, it may be applied in repair and replacement of bone.With stannous octoate as catalyst, OH of nano-hydroxyapatite which synthesized in our laboratory induces the ring-opening polymerization ofε-caprolactone. And then grafted with different quantity of lactide. HA-P(CL-LA) compound material with different ratio of nCL to nLA can be prepared. The property and structure of composite is characterized by TEM, NMR, FTIR, DSC and TEM. The result of TEM shows that HA has been dispersed homogeneously in the composites and kept original acicular or rod morphology. The result of FTIR indicates that the composite material is the copolymer of HA, PCL and PLA. The test results of1H-NMR and 13C-NMR show that the structure of composite is HA-P(CL-LA), with the feed ratio ofε-caprolactone to lactide (molar ratio) increasing, the molar ratio of caprolactone units to lactide units in the copolymer increase. And no transesterification reaction between caprolactone and lactide is observed. Only the transesterification of lactide occur, but the segment of PLA in the copolymer is isotactic sequence mainly.With the content of lactide increasing, the affection of caprolactone segment on the self-transesterification in lactide will become weaker. The result of DSC shows that Lactide impact on the crystallization of PCL, the crystallization temperature of PCL in the composites is lower than pure PCL. The appearance of a second crystallization peak with the content of LA increasing is caused byβ-form crystal of PLA. The results of GPC show that the molecular weight changes with the feed amount of lactide. When the amount of lactide increases, the molecular weight decreases correspondingly. Tensile strength of composite material is usually 13-24Mpa. With the content of soft chain (ε-CL) increasing, tensile strength of HA-P(CL-LA) decreases gradually, while elongation increases. The composite has certain flexibility and strength. Decentralization of fracture direction and clear drawbench are shown in SEM graph, the composite is a ductile fracture obviously.In order to show the difference between HA-P(CL-LA) composite and HA-P(LA-CL) composite, OH of nano-hydroxyapatite which synthesized in our laboratory induces the ring-opening polymerization of lactide. And then grafted with different quantity ofε-caprolactone to prepare HA-P(LA-CL) composite. The structure of HA-P(LA-CL) is analyzed by NMR and FTIR to find out the reason for the differences in mechanical properties between HA-P(CL-LA) and HA-P(LA-CL). The result of FTIR indicates that the composite material is the copolymer of HA,PCL and PLA. The test results of 1H-NMR show that the structure of product is HA-P(LA-CL). The result of 13C-NMR shows that the secondary transesterification reaction between caprolactone and lactide is occurred. And no the transesterification of lactide occur, only the main peak of isotactic sequence is observed. The secondary transesterification between PLA and PCL may lead that molecular weight of HA-P(LA-CL) is smaller and its mechanical properties is inferior to HA-P(CL-LA).