Characterization of Rheological Properties of Low Density Polyethylene in Torque Rheometers

Abstract

A method to evaluate the rheological properties of low density polyethylene (LDPE) using torque rheometer was developed and the parameter of Power rate model were obtained by fitting balance torque and balance temperature. The rheological parameters of polymer melts were evaluated on the basis of previous equation by introducing the apparent filling degree in torque rheometer, the results show the temperature compensated torque (Mtc) increase from 5.685 Nm to 6.972 Nm, while apparent filling degree change from 0.65 to 0.85 at the rotor speed of 29.98 rpm. TheMtcalso increase from 2,900 Nm to 3.528 Nm and increase by 0.628 Nm at the rotor speed of 4.985 rpm, while it increase by 1.287 Nm from 5.685 Nm to 6.972 Nm at the rotor speed of 29.99 rpm, which means the higher the rotor speed, the more influence on the torque. The other relative rheological parameters, such as the activation energy (ΔE), the Non-Newton (n), etc., calculated in this model, indicate the effect of apparent filling degree on the polymer melting rheology. The calculated values were compared with those derived from capillary rheolometer, the results show the apparent viscosity decrease with the increase shear rate in exponential function, the change rules of apparent viscosity are good agreement from two kinds test methods.