The melt rheology of poly(vinyl chloride) (PVC) resin has been investigated as a function of shear rate over an 80°C temperature range. The microcrystalline nature of PVC has been observed in the form of a low activation energy (δEγ)L at low temperatures and a high activation energy (δEγ)H at high temperatures. The two distinct flow activation energies suggest different rheological flow units in the low and high temperature regions. It was possible to reduce the shear stress-shear rate curves to a single master curve at 200°C by superposition of temperature and rate of shear.

SynopsisCapillary rheometry is used to characterize the thermal stability of poly(viny1 chloride). By isothermally extruding the polymer melt at constant shear rate, apparent viscosity-time relationships are obtained having three distinct regions: ( 1 ) obtainment of equilibrium viscosity, ( 2 ) constant viscosity, and (3) rapidly changing viscosity. During regions 2 and 3 the polymer extrudate gradually changes in color from water clear to black. These characteristic regions are related to the temperature of extrusion by Arrhenius plots. An activation energy of 40 kcal./g.-mole w&s calculated for the decomposition of PVC. Infrared spectroscopy, thermal gravimetric analysis, and intrinsic viscosity experiments are used to corroborate the results of the melt flow data.