Influence of crosslinking on the characteristics of thermally expandable microspheres expanding at high temperature

Authors

  • Magnus Jonsson,

    1. KTH Fibre and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology, TR 56-58, SE-100 44 Stockholm, Sweden
    2. Eka Chemicals AB, Box 13000, SE-850 13 Sundsvall, Sweden
    Search for more papers by this author
  • Ove Nordin,

    1. Eka Chemicals AB, Box 13000, SE-850 13 Sundsvall, Sweden
    Search for more papers by this author
  • Anna Larsson Kron,

    1. Eka Chemicals AB, Box 13000, SE-850 13 Sundsvall, Sweden
    Search for more papers by this author
  • Eva Malmström

    Corresponding author
    1. KTH Fibre and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology, TR 56-58, SE-100 44 Stockholm, Sweden
    • KTH Fibre and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology, TR 56-58, SE-100 44 Stockholm, Sweden
    Search for more papers by this author

Abstract

Free-radical suspension polymerization was used to synthesize thermally expandable microspheres (TEMS); in this process, a poly(acrylonitrile-co-methacrylonitrile) shell encapsulated isooctane. Different amounts of dimethacrylate, diacrylate, or divinyl ether functional crosslinker were added to investigate the effects on the crosslinking density of the polymer and the expansion properties of the TEMS. The optimum amount of crosslinker was found to be approximately 0.05–0.1 mol %. However, a significantly better expansion could be obtained with 1,4-butanediol dimethacrylate as a crosslinker, compared to 1,4-butanediol divinyl ether or 1,4-butanediol diacrylate. From monitoring the conversion of monofunctional analogues by gas chromatography, we suggest that the differences in expansion obtained with different crosslinkers, originated from the difference in the reactivity of the radicals in the system toward the vinyl functionalities of the crosslinkers. This regulated the incorporation of the crosslinker into the polymer and, thereby, the mechanical properties of the microsphere shell. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Ancillary