REACTIVE EXTRUSION OF POLYPROPYLENE WITH PULSED PEROXIDE ADDITION - PROCESS AND CONTROL ASPECTS

Controlled-theology polypropylenes (CRPPs) have been produced by using pulsed peroxide addition during reactive extrusion of a commodity res in. It has been shown that, in contrast with processes involving conti nuous peroxide addition, it is possible to independently vary the weig ht-average molecular weight (<(M)over bar (w)>) and polydispersity (PD I). The effects of peroxide pulse characteristics on the product molec ular weight characteristics have been investigated using the rheologic al properties of the CRPPs produced, and it has been found that the pu lse width, amplitude, and period provide extra degrees of freedom for controlling <(M)over bar (w)> and PDI. A simple kinetic model has been employed for process simulation, and model predictions have been used to rationalize the control options through a relative gain array (RGA ) analysis of the process. The results from this analysis have shown t hat such reactive extrusion operations are highly nonlinear and that m ultivariable control strategies would be required for large operating windows.