Preparation of Thermally Expandable Poly(acrylonitrile-co-methacrylonitrile) Microcapsules Using beta-Cyclodextrin as Pickering Emulsifier

Thermally expandable poly(acrylonitrile-co-methacrylonitrile) microcapsules were prepared by Pickering suspension polymerization. beta-Cyclodextrin (beta-CD) and polyvinylpyrrolidone (PVP) pair as the Pickering emulsifier was used as picking emulsifiers for the first time. (beta-CD is low in toxicity, cheap, and can produce particles with a relatively narrow particle size distribution. Acrylonitrile (AN) and methacrylonitrile (MAN) were used as monomers. The effects of (beta-CD content, the ratio of (beta-CD/PVP relative to the amount of monomer, AN/MAN ratio, and the various blowing agents were investigated for the preparation and properties of microcapsules. Thermally expandable microcapsules having a size of about 125 mu m were produced. When beta-CD : PVP was 2 : 1 at a total dispersant content of 3.5 wt%, the microcapsules had the best expansion performance TGA analysis confirmed that about 35% of the hydrocarbons were encapsulated in the microcapsules. Finally, it was found that beta-CD serves as a good Pickering emulsifier in suspension polymerization.