Water as Blowing Agent: Preparation of Environmental Thermally Expandable Microspheres via Inverse Suspension Polymerization

Water-encapsulated environment-friendly core–shell thermally expandable microspheres (TEMs) were prepared via inverse suspension polymerization under atmospheric pressure. Acrylonitrile (AN), methyl methacrylic acid (MMA), and methacrylate (MA) were used as monomers, and water was used as the core material. The influences of dispersants, monomer feed ratio, and cross-linking agent on the TEMs were systematically investigated. The water could disperse well in the continuous oil phase employing both 6 g spand 80 and 0.2 g calcium stearate as dispersants. When the feed ratio of AN/MMA/MA was set at 1:2:2 and 1,4-butanediol dimethacrylate was used as cross-linking agent, TEMs possessed excellent properties. The properties of melamine resin foamed by TEMs-encapsulated water were better than that of n-octane and TEMs-encapsulated n-octane.