The Preparation Of Polymer Hollow Microspheres And Morphological Control

The preparation of polymer microspheres and the control on their morphology and geometry parameters have attracted more and more attentions in recent years. Because of the especially low density, good light scattering, high specific surface area, thermal insulation properties, polymer hollow microsphereshave a wide range of applications in the light filler, high performance shading coatings,, microcapsule, leather and other fields. The preparation method and the morphology control technology is in rapid development. In this dissertation, a series of methods to prepare polymer hollow microspheres were designed; the influence of preparation parameters on microspheres morphology and geometric feature parameters were systematically studied; synthesis of thin-wall sub-micron hollow microspheres and pilot production was achieved with muchreduced sphere deformation and breakage. Furthermore, a variety of irregular particles of sub-micron to micron sizes were obtained through the synthesis process control. The main research content is as follows:1. Preparation of polymer hollow microspheres by two-step swelling phase separation methodBased on the phase separation mechanism, polymer hollow microspheres were prepared by two-step swelling process:the seed microspheresynthesis methods and technology were studied; seed microspheres with different particle sizes (150-470 nm) were synthesized and used as the template for the preparation of polymer hollow microspheres; the products were characterized by scanning electron microscope (SEM) combined with transmission electron microscope (TEM). Results show that the preparation of polymer hollow microspheres with different sizes can be realized by two-step swelling process combined with the use of different size of seed, but the surface of large size microspheres has many breakages. Only hollow spheres of small particle size can be obtained with complete shellstructure.2. Preparation of polymer hollow microspheres by dynamic swelling phase separation methodUsed solvent/non solvent synergy to form the hole, dynamic swelling phase separation method was designed and used to prepare polymer hollow microspheres:the influence of seed synthesis conditions on seed microsphere molecular weight was studied; TEM and SEM were used to characterize the morphology of hollow microspheres and the influence of seed size, shell monomers, porogen content, volume ratio of two porogen and core-shell ratios; the optimum conditions for the preparation of polymer hollow microspheres was confirmed, and pilot production was carried out. Results show that sub-micron hollow microspheres with thin but complete shell structure can be obtained by this method.3. Preparation of polymer hollow microspheres by one-step methodBased on microsuspension polymerization, the preparation of polymer hollow microspheres was achieved via one-step method. Two monomer emulsification process including high-pressure homogenization process and high-speed stirring processes were involved for preparing polymer hollow microspheres, respectively. In the study on high-pressure homogeneous process, the thesis explored the influence of homogenizing pressure and emulsifier on sphere morphology; in the study on high mixing technology, the amount of initiators, porogens and functional monomers and their adding protocol on the particle morphology were investegated; the product was characterized by SEM and TEM. The results show that, in homogenization process, at appropriate pressure and the presence of emulsifier, sub-micron polymer hollow microspheres and solid microspheres can be obtained by one-step method; in high stirring process, micron-sized spheres were prepared whose morphology is controlled by the process conditions. Solid microspheres, hollow microspheres, porous microspheres, vesicles, bowl, poached egg and boat shaped particles can be separatly obtained by changing the synthesis parameters.