Pyroelectric properties of linear aromatic polyurethanes

Two types of aromatic polyurethanes, poly(hexamethylene phenyl dicarbamate) (PUH6) and poly(heptamethylene biphenylene dicarbamate) (PUB7) have been synthesized by the polycondensation method. Structural, pyroelectric and dielectric properties of these polyurethanes were studied. The pyroelectric activity was studied in the temperature range from room temperature to 120/spl deg/C for poled samples of both polyurethanes. The temperature dependence of the pyroelectric constant of both polyurethanes vanished around their glass transition temperatures. The experimental results given in this paper suggest that the pyroelectric behavior is possibly attributed to orientation of the urethane dipole in the amorphous phase. The pyroelectric coefficients obtained are 13 and 15 /spl mu/m/sup -2/K/sup -1/ for the PUH6 and PUB7 samples, respectively.