An apparatus for measuring the thermal conductivity and viscosity of polymers under shearing strain

Abstract

Due to the difficulty of finding an appropriate method and experimental set-up to measure thermal conductivity in shear flow, there have been very few publications about the effect of orientation on thermal conductivity in shear flow in the literature and viscosity is generally measured separately by using a different experimental set-up. In order to measure simultaneously the thermal conductivity and viscosity of polymer melts in shear flow, a concentric cylinder thermal conductivity cell which is similar in principle to a Couette viscometer has been built. Thermal conductivity can be measured at temperatures approaching and at strain rates up to . The outer cylinder may be rotated at the desired speed of rotation, while the inner cylinder which is stationary has a strain gauge mounted on its top in order to measure the torque and therefore the viscosity. The gap of 2 mm between the two cylinders is filled with polymer melt. The thermal conductivity is measured by a transient plane heat source method which consists of generating heat at a constant rate by using the nickel wire wrapped around the periphery of the inner cylinder and recording the temperature rise of the nickel wire as a function of time. The measurement process and the speed of the motor are controlled by a microcomputer.