New models of radical polymerization with branching and scission predicting molecular weight distribution in tubular and series of continuous stirred tank reactors allowing for multiradicals and gelation

Modeling of the mol. wt. distribution (MWD) of low-​d. Polyethylene (ldPE) has been carried out for a tubular reactor under realistic non-​isothermal conditions and for a series of CSTR's. The model allows for the existence of multiradicals and the occurrence of gelation. The deterministic model is based on a Galerkin finite element approach (FEM) and employs the pseudo distribution concept to address the no. of radical sites per chain as the second dimension next to chain length. The Galerkin method is shown to allow a straightforward and compact formulation of the series of CSTR's using a repetitive matrix structure with connective elements. The 'topol. scission' model is utilized as the closest approxn. of random scission in deterministic modeling accounting for the highly branched character of the system As conditions of ldPE polymn. lead to broad MWD and are close to gelation, allowing for gel turns out to be crucial. It was obsd. that a broad MWD in a single CSTR becomes narrower as the no. of CSTR's in series increases and is narrowest in the batch reactor.