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The Study on the Synthesis of Thermally Expandable Microspheres

Author: ZuoKeCun
Tutor: LiuFeng
School: East China University of Science and Technology
Course: Materials Science and Engineering
Keywords: Heat-expandable microspheres Foaming properties Suspension polymerization
CLC: TQ316.335
Type: Master's thesis
Year: 2012
Downloads: 56
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Abstract


Having a core-shell structure of the heat-expandable microspheres can be successfully prepared by suspension polymerization. The study showed that the phase was added to the oil phase containing a monomer such as acrylonitrile, respectively, can be prepared having good foaming properties of the microspheres in the water of different dispersants. An advantage of using magnesium hydroxide as a dispersant has a ratio of the microspheres obtained with silica prepared magnesium hydroxide easily be able to after the end of the reaction, by adding hydrochloric acid to remove, which is advantageous for industrial production. Silica dispersant system, the particle size and size distribution of the influence factors. The study found that the nearly saturated sodium chloride can be eliminated caking and floc is generated. The microspheres obtained in the addition of baffles or chunky type reaction vessel having a smaller particle size and a more narrow size distribution. In some extent, increase the stirring speed can be obtained finer microspheres, but by stirring Assembly destruction of the initial production of the reaction particles. This system also studied the impact of the reaction conditions on the foaming properties. The smaller the particles the greater the expansion of the internal pressure required to concentrate the higher the foaming temperature. The higher the boiling point of the blowing agent concentrate the higher the foaming temperature. More foaming agent, the the concentrated foaming temperature is lower, the amount of 30% can be obtained medium foaming temperature, foam stabilizing properties, the large expansion ratio of the microspheres. Add different Tg and chemical properties of the third monomer, the foaming properties of the microspheres have a greater impact on the use of butyl acrylate as the third monomer has good foam stabilizing properties. Magnesium hydroxide as a study of the preparation of microspheres of the dispersing agent as an initiator, BPO, 70 ° C reaction temperature, 0.4% crosslinker TM, 3.3% initiator dosage and 11% DMAA obtained microspheres having good foam stabilizing performance. To make the microspheres having a higher expansion ratio, the amount of foaming agent used is higher than 28%. In the oil phase was added having a higher glass transition temperature of the N, N'-dimethyl acrylamide (DMAA) and other monomer, by studying the the foamed law to adjust formulation and process, it is possible to obtain the high-temperature foaming microspheres, issued The bulb temperature may be higher than 190 ° C, and can be maintained in a long temperature range. In the preparation process of the high temperature foam microspheres, the 11% DMAA can be obtained a high foaming temperature, and the larger expansion ratio of the microspheres, with 27.8% of the blowing agent and 0.22% of the TM has better foam stabilizing properties. In addition, the solvent properties of high temperature foam microspheres found soaked in xylene did not affect its foaming properties. The different polarities solvent of microspheres with different degrees of damage. The dry microspheres stored at room temperature and atmospheric pressure for six months not affect its foaming properties.

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CLC: > Industrial Technology > Chemical Industry > Molecular compound Industries ( polymer industry ) > Production process > Polymerization process. > By method of sub- > Suspension polymerization ( into beads polymerization )
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