Preparation and characterization of conducting polymer-coated thermally expandable microspheres

The thermally expandable microspheres(TEMs) were prepared via suspension polymerization with acrylonitrile(AN), methyl methacrylate(MMA) and methyl acrylate(MA) as monomers and n-hexane as the blowing agent. Meanwhile, a novel type of functional and conductive thermal expandable microsphere was obtained through strongly covering the surface of microsphere by conductive polymers with the mass loading of 1.5%. The optimal conditions to prepare high foaming ratio and equally distributed microcapsules were investigated with AN-MMA-MA in the proportion of 70%/20%/10%(m/m/m), and 25 wt% of n-hexane in oil phase. The further investigation results showed that the unexpanded TEMs were about 30 μm in diameter and the maximum expansion ratio was nearly 125 times of original volume. The polypyrrole(PPy) was smoothly coated on the surface of the TEMs and the expansion property of PPy-coated TEMs was almost the same as the uncoated TEMs. Moreover, the structure and expanding performance of TEMs and PPy-coated TEMs were characterized by scanning electron microscopy(SEM), laser particle size analyzer and dilatometer(DIL).