| Summary: | 碩士 === 南台科技大學 === 化學工程與材枓工程系 === 100 === Polylactide (PLA) is one of the promising biopolymers, which can find wide applications, such as bottles, electrical appliances, food packaging bags, with good biocompatibility, biodegradability, and excellent mechanical properties. This work is to study the manufacture of PLA microparticles using the emulsion solvent evaporation method and the solvent precipitation method and to investigate their thermal properties and the feasibility of being an alternative option for plastisol resins.
In the emulsion solvent evaporation method, PLA was dissolved in dichloromethane, and dispersed in surfactant-containing aqueous solutions, followed by the removal of solvent. The resulting PLA microparticles were investigated by scanning electron microscopy (SEM) to obtain an average particle size between 1.7-8 m. The average particle size increases with increasing surfactant concentration and homogenizer speed, but decreases with increasing PLA content. Plastisols can be successfully prepared from the PLA microparticles; however, solid products cannot be made from compression molding due to the release of plasticizers during the process.
In the solvent precipitation method, PLA was dissolved in ethyl acetate or toluene at high temperatures, followed by a quenching operation or adding of non-solvents to obtain precipitates. The phase diagram of both solutions was constructed by using the cloud point measurement. The morphology of the PLA precipitates was found to change from an interconnneted network structure to a lamellae structure with increasing dissolution temperature. There was no significant change observed for the precipitate with varying PLA concentrations or cooling temperatures. The failure in preparing PLA microparticles by the solvent precipitation method is speculated to be due to the crystallization of PLA along a preferred orientation, rather than isotropic precipitates, which is confirmed by the presence of high PLA crystallinity of up to 70% for the precipitates, when compared with the raw PLA (34%).
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