Preparation Of Polylactic Acid Microparticles And Magnetic Composite Materials By Supercritical Fluid Antisolvent Technology

Microparticles of polylactic acid have very large specific surface area and surface tension, which show many specific functions in related applications. In addition, magnetic composite microspheres have important research value due to its unique orientation.In this paper, we use the new efficient supercritical fluid anti solvent technology to prepare poly lactic acid particles firstly, using single factor experiments to investigate the effects of different process parameters on the particle size of the product. The experiment uses a supercritical fluid forcibly dispersed solution prepared polylactic acid microspheres, by the basis of single factor experiment investigated various operating conditions (type of solvent, pressure crystallization, the crystallization temperature of the polylactic acid concentration) of product size influence, also by choosing the solvent and the concentration ratio of the polylactic acid, crystalline pressure, the crystallization temperature, the proportion of co-solvent 4 factors are to L9 (34) orthogonal test. Through experiments concluded:selection of a certain percentage of the concentration of particulate diameter ratio of the solvent methylene chloride and acetone is prepared in a relatively smaller, more evenly distributed; The concentration of poly lactic acid increased and the particle size increases; It helps produce smaller particles by increasing pressure; High temperature can easily lead to particles melt and film agglomeration. Experimental validation summary, the best experimental conditions selecting is:the concentration of 7 mg/ mL, crystallization pressure 16 MPa, temperature 38 ℃, methylene chloride:acetone =2:1, to form the relevant conclusion at the same time.Then, the study on the modification of poly lactic acid was carried out. The first use of the gas anti-solvent precipitation technique for preparing PLA/Fe3O4 composite magnetic microspheres and its related properties are studied. Experiment with dichloromethane as the solvent, CO2 as the anti-solvent, at a temperature of 45 ℃, 10MPa pressure, at a lower solution flow rate of 0.8ml/min condition, using supercritical crystallization equipment provided by Applied Separations company of the United States is to obtain a composite microspheres. And to analysis and characterization by infrared spectroscopy, scanning electron microscopy and vibrating sample magnetometer and so on. The results show:the composite particles stable structure, good performance, good dispersibility, particle size was prepared as 2.239 μm. magnetization as 11.824 emu/g. This study shows that the supercritical anti-solvent technology polylactic acid microspheres magnetic composites technology is feasible, providing a new research idea of the production and preparation of the magnetic microspheres. Compared with the conventional method, prepared by supercritical anti solvent method has smaller particle size of magnetic microspheres, more uniform distribution of the solvent can be recycled, without any pollution, by changing the process parameters can better control the particle size and particle size distribution in the preparation process, can be prepared to meet the different requirements of particle.