Polyurethane acrylate (PUA) are widely used as coating for automobile industry. Making these coatings electrically conductive would open up new applications. Using thermally reduced graphene (TRG) and in-situ polymerization we have created PUA nanocomposites with an ultralow percolation concentration of 0.15 wt% (0.07 vol%) graphene. Urethane-acrylate oligomer (UAO) was synthesized and diluted by tripropyleneglycol diacrylate (TPGDA) to form flowable UAO/TPGDA mixture (UA). TRG was solvent-blended in UA to form uncured TRG/UA liquids and were polymerized by free radical polymerization with azobisisobutyronitrile (AIBN) initiator. Percolation concentrations of polymerized TRG/PUA nanocomposites occurred at 0.15 wt% (0.07 vol%), as determined by surface resistance measurements, bulk electrical conductivity, and modulus. TEM images revealed a homogeneous dispersion of TRG in PUA. Differential scanning calorimetry (DSC) was used to monitor the polymerization of TRG/UA uncured liquids and thermal properties of polymerized TRG/PUA nanocomposites. Polymerization heat, glass transition temperature, and polymerization temperature are independent of TRG loading, though polymerization temperature is ∼10 °C lower in the absence of TRG.
Bibliographical noteFunding Information:
The authors would like to acknowledge Prof. Andreas Stein, Dr. Hyunwoo Kim and Mr. Wei Xie for helpful discussions and support from the Abu Dhabi-Minnesota Institute for Research Excellence (ADMIRE); a partnership between the Petroleum Institute of Abu Dhabi, and the Department of Chemical Engineering and Materials Science at the University of Minnesota. We also thank Vorbeck Materials for providing the TRG. This work utilized the University of Minnesota College of Science and Engineering Characterization Facility, which receives partial support from the NSF-NNIN program and capital equipment funding from the NSF through the MRSEC program.
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- Urethane acrylate