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The Study on the Biodegradable Polylactic Acid Composites

Author: SunLiLi
Tutor: LiuDeBao
School: Tianjin University of Technology
Course: Materials Physics and Chemistry
Keywords: Polylactic acid Nano - hydroxyapatite Magnesium particles Preparation and Properties
CLC: R318.08
Type: Master's thesis
Year: 2011
Downloads: 80
Quote: 0
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Abstract

Polylactic acid (polylactide, PLA) is a biodegradable polymer, its good biocompatibility has been recognized by the United States Food and Drug Administration (FDA). Its ultimate degradation products are CO2 and H2O, the intermediate product of lactic acid is also a normal glucose in the body, therefore, the polylactic acid-organisms will not produce adverse effects in vivo degradation, the mechanical strength is gradually decreased in the degradation process in the body, can stress slowly transferred to the fracture site, to avoid stress shielding effect, but also has good thermal moldability, and is an ideal implanted material. However single polylactic acid as bone fixation materials lower absolute mechanical strength; acidic degradation products, and easily cause aseptic inflammation in the body; lack of osseointegration capacity; penetrating X-ray, clinical development observed shortcomings is not easy . Therefore, the polylactic acid is modified to improve its performance as a hotspot. Firstly, using the composite nano-hydroxyapatite (n-HA) and polylactic acid, improve the initial hardness and rigidity of the material, slow the rate of degradation of the material in the early to hydroxyapatite nanoparticles surface modified by gelatin to improve polylactic acid matrix interface bonding strength; nano-hydroxyapatite particles dispersed evenly degree of polylactic acid matrix composites, nano-hydroxyapatite sol system. As hydroxyapatite, is difficult to dissolve and absorb the polylactic acid after the in vivo degradation caused by local acidic environment and the role to be improved. Therefore has good biocompatibility and its degradation process of this characteristic of the alkaline metallic magnesium, the magnesium granules compounded with the polylactic acid, midterm and the local acidic environment after the degradation of the polylactic acid, and to reduce the irritation on human tissue. The Mg / PLA composite melt mixing method and its characterization and performance study. Our results show that: 1 through gelatin chemical surface modification of nano-hydroxyapatite particles, can be achieved key binding to hydroxyapatite particles and polylactic acid matrix interface, help to improve the interfacial bond strength of composite materials. 2, the use of nano-hydroxyapatite sol system under the composite help hydroxyapatite particles are uniformly dispersed in the polylactic acid matrix. 3, the study found that the mechanical properties of the composites with the increased content of hydroxyapatite, the mechanical strength first increases and then decreases, there is an optimum range of particle content in the preparation conditions of about 5%. Mg particles addition, although the lower tensile strength, but the bending strength of the composite material is increased. 4, the degradation in the composite material in vitro experiments, the adsorption layer is formed apatite n-HA/PLA composites exhibit good biological activity, the surface of the composite material; the hydroxyapatite nanoparticles Add improve the degradation of the pure poly lactic acid acidic; magnesium particles added to further improve the acidic environment in the degradation of the polylactic acid. 5, both n-HA/PLA and Mg / PLA composite biological friction characteristics: As the load increases the wear resistance of the composite decreases. Nano hydroxyapatite particles with magnesium metal particles are added to help improve the wear resistance of the polylactic acid substrate.

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CLC: > Medicine, health > Basic Medical > Medical science in general > Biomedical Engineering > General issues > Biomaterial
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