Molecular weight/branching distribution modeling of low-density-polyethylene accounting for topological scission and combination termination in continuous stirred tank reactor

We present a comprehensive model to predict the molecular weight distribution (MWD),¹1Molecular weight distribution. and branching distribution of low-density polyethylene (ldPE),²2Low density polyethylene. for free radical polymerization system in a continuous stirred tank reactor (CSTR).³3Continuous stirred tank reactor. The model accounts for branching, by branching moment or pseudo-distributions. The common free radical polymerization reactions including chain scission have been considered in the model. Non-linear or the so-called topological scission has been modeled using approximate fragment length distributions derived from scission, applied to branching topologies. To model the distributions, the Galerkin-FEM method based on the same principles as PREDICI^® has been applied and implemented in MATLAB^©. The fundamental numerical problem arising from topological scission has been solved. Thus, the model provides more accurate results, allowing a precise comparison to earlier results and to Monte Carlo simulations.