FLOW AND THERMAL-STABILITY OF RIGID PVC

Experimental methods of measurement of the flow velocity distribution of a rigid PVC through a slit and a cylindrical die were developed. In particular, the slip of the polymer at the wall of a slit die has been shown by the optical observation of the displacement of tracers mixed with the melt. The effect of lubricants on the flow velocities has been shown and a law of variation of the fluid velocity at the wall has been pro-nnspd. These data, brought together with the kinetics of the PVC thermal degradation, can be used to compute the transit time of the polymer in a die and a thermal residual stability after extrusion. On this basis, it is possible to adjust the output rates, the temperatures, or the geometrical parameters to obtain a product of constant quality during a long extrusion time. © 1979, The Society of Rheology. All rights reserved.