Preparation and properties of thermoexpandable polymeric microspheres

In this paper, thermoexpandable polymeric microspheres were prepared by suspension polymerization with acrylonitrile (AN) and methyl methacrylate (MMA) as monomers and i-butane as a blowing agent. The micromorphology and thermal stability were researched by polarized microscopy and TGA. The diameter of the expandable microspheres increased from about 20 μm (unexpanded) to 40-80 μm (expanded) upon heating. The maximum expansion volume was higher than 22 times of the original volume and the density of the expanded microspheres was about 16.7 kg/m3. The blowing agent content in microspheres was about 20 wt% and T_o.e., T_m.e. and T_o.s. were 80 ℃, 120-130℃ and 140-145 ℃, respectively.