Synthesis of urethane acrylate based electromagnetic interference shielding materials

In this work, a new method, consists of synthesis of urethane acrylate (UA) followed by in situ polymerization of pyrrole using cerium (IV) as an oxidant and UV-curing of the composites, for preparing polypyrrole-UA (PPy-UA) composite films was described. It appeared that dielectric constants of the composites increased with increasing the PPy content and decreased with increasing the frequency from 10^-2 to 10⁷, indicating an interfacial Maxwell-Wagner contribution to the permittivity. An incorporation of a small amount of PPy (15% Py) to UA matrix increased their dielectric constants more than 4 × 10⁴ (41,259) at 10^-2 Hz. So, the incorporation of PPy was very effective for enhancing the dielectric properties of UA matrix. Furthermore, the significant enhancement in dielectric properties (loss tangent and dielectric constant) contributes to the improvement in electromagnetic interference shielding efficiency. Composite films were characterized using Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectrophotometer and ¹H-NMR. It was seen that PPy is blended with the UA matrix at the molecular level through H-bonding interactions. A linear relationship was also observed between the characteristic groups' absorbances of PPy (from FTIR-ATR) and dielectric constant values (from dielectric spectrometer). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013