| The research on the fracture innerfixation composites is one of the most attractive aspects of biomedical engineering. For a long time, the metal was the traditional fracture innerfixation for its very strong mechanics strength, but it could not be degraded and absorbed in the human body. So the second operation would be needed to take out the metal bolt. Patients should be very pain and need more money. Therefore, it has become an aim for most scientists to make one fracture innerfixation materials that could be degraded and absorbed in the human body. It has made the aim come true that PLLA came to the world. PLLA possessed no toxicity and harm to human body, and provided with the all right biocompatibility and very strong mechanics intension. PLLA could degrade slowly when it was embedded into the body, and would become to CO2 and H2O after degradation. Up to now, the fracture innerfixation materials that could be degraded and absorbed were almost simplicity polymer materials in the market. There were still many defects in these materials, such as complex facture technics, valuableness price, and rapidly intension degradation. The traditional β-tricalcium phosphate(β-TCP) bioceramic possessed a component similitude with bone mineral, and a good biocompatibility and perdurable erode. But β-TCP appeared a big brittleness and a poor toughness while it was used singly, which limited its application in clinic. To meet the demand for mechanical and biological properties of bone replacement materials, most people have started to study composite materials between β-TCP and polymer. In this dissertation, the emphases are to prepare β-TCP/ Poly L-latic acid (PLLA) composites with excellent mechanical and biological prosperities, especially to pay attention to the biodegradation, the mechanics, the easy machining. 1. High-purity and ultrafine CaCO3 powers were mixed to slurry with water, and were poured rapidly into phosphoric acid solution with Ca/P=1.50, stirring phosphoric acid solution and ultrasonic agitation to precipitate TCP precursor. Next, the β-TCP ultrafine power was prepared by calcining TCP precursor at 950℃. 2. A process which consists of a solvent casting stage, a film crush up, and a compression molding stage has been used to fabricate fracture innerfixation composite materials of β-TCP/PLLA according to the weight percentage of β-TCP %=0%, 20%, 30%, 40%, and 50% in this study. During the preparation of composites, the effects of molding temperature, molding pressure, disperse of the β-TCP in the PLLA, content of the β-TCP, and warm-up time on mechanical properties, degradation in vitro of composites have been studied. Scanning electron microscope (SEM) observation indicated that β-TCP was dispersed uniformly in chloroform solution of the PLLA under the ultrasonic condition, and the composite was compact. The Compressive yield strength and the bending strength of the composite were nearly 75MPa and 80 MPa. The experimental results showed that the β-TCP/PLLA composite materials manufactured under the conditions of low molding pressure, 15min warm-up, 200℃molding temperature and 20wt% β-TCP would possess a much better mechanical strength. The measurement of the melting point and the crystallinity with DSC would provide a test data to molding temperature and degradation of composites. 3. The degradation of β-TCP/ PLLA composites in vitro has been studied in stimulated body fluid (SBF). The degradation in vitro was carried out throughimmersing the composites into SBF at 37℃, and sampling respectively after 1, 3, 6, 9, 13, and 17weeks. Molecular weight of PLLA, mechanical strengths and microstructure changes were measured, and the samples were characterized by FTIR, SEM, and XRD. The results showed that bone-like apatite was formed on the surface of composites, and the mechanical strengths continuously descend with the time of degradation. The decline of mechanical strength was different with the content of β-TCP.
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