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Synthesis and Characterization of Biodegradable PDLLA

Author: SongJie
Tutor: ZuoYuHua
School: Wuhan University of Technology
Course: Materials Science
Keywords: Polylactic acid PDLLA Ring-opening polymerization Lactide Influencing factors
CLC: TQ317
Type: Master's thesis
Year: 2004
Downloads: 525
Quote: 1
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Abstract


Polylactic acid (PDLLA) has good biocompatibility, biodegradable, its ultimate degradation products are carbon dioxide and water to be excreted by the body's normal metabolism, so it is widely used in surgical sutures, burns covering fractures within fixing material like. As fracture fixation materials critical to ensure that the initial mechanical strength meet repair cancellous bone fractures requirements, for the synthesis of high molecular weight polylactic acid conditions is the focus of this paper. Preparation of polylactic acid are mainly two ways: direct condensation method and ring-opening polymerization. The low molecular weight of the polylactic acid prepared by direct polycondensation, and broad molecular weight distribution. Its mechanical properties can not meet certain requirements in the bio-medical. Therefore, currently the most commonly used method for the preparation of high molecular weight polylactic acid (PDLLA), ring-opening polymerization, i.e. by the D, L-lactic acid synthesis propionyl lactide, polylactic acid is formed by ring-opening polymerization from lactide. In this paper, the ring-opening polymerization with D, L-lactic acid synthesis of PDLLA. This synthesis reaction is mainly divided into two steps - the synthesis of lactide and lactide ring-opening polymerization. The first polylactic acid oligomer by dehydration and then by raising the temperature so that the cleavage of the oligomer obtained lactide, synthesis of lactide stannous octoate catalysis under reduced pressure under the action of the catalyst of ZnO obtained by polymerization of PDLLA. , Through the improvement of the reaction apparatus in the process of synthesizing lactide solve the problem of clogging of the lactide and improve the yield of lactide; through research catalyst amount, dehydration temperature, the time of dehydration, dehydration and depolymerization temperature, depolymerization time influence on the reaction, to determine the optimum conditions of the synthesis of lactide. By characterization, of the lactide in the crude lactide and purified to determine the purity of the lactide and purification process. Lactide polymerization factors, the main body purity, the amount of initiator, polymerization temperature, polymerization time, polymerization of the vacuum degree. After synthesized PDLLA molecular weight in the different conditions of the test results show that by controlling the polymerization reaction conditions to obtain a high molecular weight PDLLA, main process parameters: mass ratio of initiator to monomer is about 0.03%, the polymerization temperature in the about 140 ℃, polymerization time 48h, the polymerization vacuum for a 0.05 mm Hg.

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