Short-chain branching distribution oriented model development for Borstar bimodal polyethylene process and its correlation with product performance of slow crack growth

This work aims to develop a model that can predict the short-chain branching distribution (SCBD) of bimodal polyethylene (BPE) for an industrial Borstar process and correlate it with an updated structure-performance model (SPM) to estimate the slow crack growth (SCG) performance of the product. To calculate the SCBD and molecular weight distribution (MWD) simultaneously, a rigorous process model (i.e., kinetic model, thermodynamic model, reactor model) combined with a specific calculation method is established. The predicted SCBD and MWD of BPE are in good agreement with the plant data. An updated SPM that allows the estimation of the SCG resistance of BPE from its molecular architecture is developed, taking the effect of SCBD into account. The SPM reveals that the predicted SCG performance of BPE will be underestimated when only the average SCB content will be considered. The process model is coupled with the updated SPM, and it is capable of a full assessment on the effects of various operating conditions on the SCBD link with the MWD and, in turn, the SCG performance of BPE produced in the Borstar process. The underlying relationships are also discussed.