Loss Angle Testing of Polymer Melts at High Shear Rate

Theoretical and experimental study of loss angle of polymer melts at high shear rate was done based on multi-function and all-electric rheometer (MAR) designed by the authors. The phase difference of the dynamic components of shear strain and shear stress at the capillary wall proved to be as same as the phase difference of superimposed vibration displacement and the entrance pressure. In order to get the loss angle, the intrinsic vibration displacement was defined and original signal was transformed from time domain representation to frequency domain representation by DFT. The experiment results show that the loss angle increases greatly with the increase of the superimposed vibration displacement frequency. It indicates that the viscous losses increase while the elastic properties decrease with the increase of the superimposed vibration displacement frequency. The loss angle didnt change notably with the increase of the piston steady velocity and the superimposed vibration displacement amplitude. This indicates that the viscoelastic properties keep consistence when the shear rate and piston amplitude changes.