Nano-hydroxyapatite/Organic Hybrid Materials Preparation Andproperties Research

The composites of PLA/n-HA have great potential applications as bioartificial bone repair materials for current. Polylactide(PLA) has been widely used in various biological fields due to its good mechanical property and necessary biodegradability and biocompatibility. Most important of all, its degradation products are ingestible in human bodies. However, there may be aseptic inflammation in the degradation process. And PLA has no bone conduction. n-HA is a main component of bones and teeth in human beings and many animals. It has a great capability of biological activity, and thereof can be syncretized with the natural bone by chemical bonding reaction. But, n-HA has high brittleness, poor toughness. It is lack of biological signal on the surface. Based on the background, on the one hand, this paper prepared n-HA modified with PDLA on its surface. Then, that the PDLA-n-HA mixed with PLLA prepared the uniform structure of hydroxyapatite and PLLA composites via interaction between PLLA and PDLA. What is more, the relationship between the properties of composites and ratio of PDLA-n-HA and PLLA was also investigated. On the other hand, this article conducted a series of modification research on the surface of n-HA. The main research work of this paper is as follows:The preparation of PDLA-n-HA/PLLA hybrid materials is as follows. First of all, we prepared n-HA by chemical precipitation method. Secondly, Sn(OCt)2 as catalyst, PDLA-n-HA was prepared by ROP of monomer D-LA using the surface hydroxyl groups of n-HA as a initiator. At the same time, synthesis of high molecular weight(Mn≈1×104)PLLA was carried out via ROP of monomer L-LA using benzyl alcohol as initiator. Finally, PDLA-n-HA/PLLA hybrid materials were obtained by the stereocomplex of PDLA-n-HA and PLLA and hot press molding. The materials were characterized by TEM, SEM, Rheology and Mechanical property test.The results showed that when the content of PDLA-n-HA is 10wt%, the MI of PDLA-n-HA/PLLA hybrid material is minimum(27.36 g/10 min). The tensile strength of PDLA-n-HA/PLLA hybrid material which contains 10% of PDLA-n-HA is max( 60.37 Mpa). Its elongation at break is 9.50% and the notched Izod impact strength is 39.88J/m. At the same time, we also tested the rheological behavior of the hybrid materials, thus the viscoelastic properties of hybrid material was discussed from the micro perspective.The modification of n-HA is as follows. This paper also tested the modification of n-HA with silanecoupling agent CG-550, CG-560, CG-171, CG-1631, and investigated the basic properties of the modified n-HA.The results showed that various coupling agent is successful to modify the n-HA. The n-HA which was modified by the CG-171 and mercaptoethanol weight gains of 9.5%. The dispersing stability of n-HA, N1631-n-HA and PDLA-n-HA in chloroform was tested. The trial results showed that the n-HA modified by CG-N1631 make a slight increase in particle dispersion of n-HA. The suspension stability of PDLA-n-HA in chloroform greatly improved. And the stability can be maintained at more than 26 h.