| Abstract: | Chlorinated poly(vinyl chloride) (CPVC) is known to have a higher softening temperature than conventional poly(vinyl chloride) (PVC). Its processability characteristics are, however, different; it has been reported that CPVC is more difficult to process. However, only limited information on the processability characteristics is available. This paper describes some studies of the flow behavior of CPVC melts in a capillary rheometer. The true melt viscosity and activation energy were determined between 190° and 210°C for a number of samples, and they appear to be related to the cohesive energy density of the samples. It was observed that melt fracture, i.e., gross distortion of the extrudate, occurs even at low shear rates in samples having a high chlorine content. This has been attributed to the relatively high pressures that have to be used, the pronounced non-Newtonian nature of the melt, and melt elasticity. It is postulated that melt elasticity could result from crosslinking at the site of the double bond which is known to be formed by dehydrochlorination. |
