Abstract
The thermally expandable microspheres (TEMs) were prepared through suspension polymerization with acrylonitrile (AN), methyl methacrylate (MMA) and methyl acrylate (MA) as the main monomers. Simultaneously, iso-pentane, n-hexane, iso-octane and other low-boiling hydrocarbons were prepared as blowing agents under two conditions, including high-pressure nitrogen and atmospheric conditions. The above physical foaming microspheres have a core-shell structure and excellent foaming effects. A layer of polyaniline (PANI) was deposited on the surface of the prepared TEMs by emulsion polymerization to obtain conductive and heat-expandable microspheres. Afterwards, the foaming ink was prepared by mixing the conductive TEMs and water-based ink. Finally, a conductive three-dimensional picture was obtained by screen-printing technology. This paper specifically focuses on the effects of particle size, morphology and the thermal expansion properties of the microspheres. The present research methods expect to obtain microspheres with a high foaming ratio, uniform particle size and antistatic properties, which may be applied to physical foaming ink.
Highlights
In the early 1970s, Dow Chemical Co. first reported the preparation methods of foaming microcapsules in its patents [1], and the research about foaming microcapsule preparation has developed rapidly since [2,3,4,5,6]
The following reagents were obtained from commercial suppliers and were used without further purification: Acrylonitrile (AN), 99 wt %; methyl methacrylate (MMA), 99 wt %; azodiisobutyronitrile (AIBN), 98 wt %; methyl acrylate (MA), 95 wt %; 1,4-butanediol dimethyl acrylic (BDDMA), 99 wt%; MgCl2 ·6H2 O, 95 wt %; n-hexane, 99 wt %; sodium hydroxide, 99 wt %; sodium chloride, 99 wt %; HCl, 37 wt %; cyclohexane, 99 wt %; sodium dodecyl sulfate, 95 wt %; aniline, 99 wt %; ammonium persulfate, 99 wt %
The larger particle size of the microcapsules and the more core materials coated in the microspheres resulted in the higher expansion ratio
Summary
In the early 1970s, Dow Chemical Co. first reported the preparation methods of foaming microcapsules in its patents [1], and the research about foaming microcapsule preparation has developed rapidly since [2,3,4,5,6]. The interior materials of physical foaming microcapsules are generally organic solvents with low boiling points and spherical shells that are thermoplastic polymer coats. When the microcapsules are heated, the heart materials (low boiling point organic solvents) rapidly evaporate with internal pressure production, and the wall materials begin to soften and expand simultaneously. Suspension polymerization is the most common method used to prepare physical foaming microcapsules [21,22]. This study proposes to prepare foaming microcapsules by the suspension polymerization method under high-pressure nitrogen and atmospheric air conditions. A kind of novel microcapsule with special core-shell structures and physical foaming-conductive ink will be prepared based on the research of structure and properties
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