The Study On The Synthesis Of Thermally Expandable Microspheres

Thermally expandable microspheres which have core-shell structure can be successfully preparation by suspension polymerization in different aqueous phase. Using magnesium hydroxide as dispersion stabilizer is better than silica, because the former can be easily removed by adding hydrochloric acid after reaction. And that is suitable for industrial production.Influencing factors on particle size and distribution had been studied in silica system. Agglomeration and floccules can be eliminated by adding saturated sodium chloride. Using pyknic type reaction kettle or placing baffles can reduce particle size and narrow size distribution. Increasing mixing speed can reduce particle size, but particles will be broke if stirring too fast. Influencing factors on foaming performance also had been studied. The smaller the particle is, the higher the concentrated foaming temperature is. The more the foaming agent used, the lower the concentrated foaming temperature is, and 30% foaming agent is better. Adding the third monomers which having different Tg and chemical property can affect foaming performance and butyl acrylate gave microspheres better foam stabilization performance.In magnesium hydroxide system, microspheres with better foam stabilization performance can been synthesized using 0.4% TM as cross-linking agent,3.3% BPO as initiator,11% DMAA at 70℃. With at least 28% isooctane as foaming agent was used, microspheres had higher expansion ratio.High temperature foaming microspheres can be preparation through using DMAA as complementary monomer.11% DMAA can give microspheres higher foaming temperature and expansion ratio.27.8% isooctane and 0.22% TM can give microspheres better foam stabilization performance. What's more, solvent resistance performance of microspheres had been studied and we found that dimethylbenzene had no effect on foaming performance. But polar solvent have a great impact upon microspheres performance. The good news was that dried microspheres foaming performance stayed the same after half a year at room temperature.